77 results found
Sharma SK, McLean K, Colgan RJ, et al., 2021, Combining conventional QTL analysis and whole-exome capture-based bulk-segregant analysis provides new genetic insights into tuber sprout elongation and dormancy release in a diploid potato population., Heredity, Vol: 127, Pages: 253-265, ISSN: 0018-067X
Tuber dormancy and sprouting are commercially important potato traits as long-term tuber storage is necessary to ensure year-round availability. Premature dormancy release and sprout growth in tubers during storage can result in a significant deterioration in product quality. In addition, the main chemical sprout suppressant chlorpropham has been withdrawn in Europe, necessitating alternative approaches for controlling sprouting. Breeding potato cultivars with longer dormancy and slower sprout growth is a desirable goal, although this must be tempered by the needs of the seed potato industry, where dormancy break and sprout vigour are required for rapid emergence. We have performed a detailed genetic analysis of tuber sprout growth using a diploid potato population derived from two highly heterozygous parents. A dual approach employing conventional QTL analysis allied to a combined bulk-segregant analysis (BSA) using a novel potato whole-exome capture (WEC) platform was evaluated. Tubers were assessed for sprout growth in storage at six time-points over two consecutive growing seasons. Genetic analysis revealed the presence of main QTL on five chromosomes, several of which were consistent across two growing seasons. In addition, phenotypic bulks displaying extreme sprout growth phenotypes were subjected to WEC sequencing for performing BSA. The combined BSA and WEC approach corroborated QTL locations and served to narrow the associated genomic regions, while also identifying new QTL for further investigation. Overall, our findings reveal a very complex genetic architecture for tuber sprouting and sprout growth, which has implications both for potato and other root, bulb and tuber crops where long-term storage is essential.
Parry G, Benitez-Alfonso Y, Gibbs DJ, et al., 2020, How to build an effective research network: lessons from two decades of the GARNet plant science community, JOURNAL OF EXPERIMENTAL BOTANY, Vol: 71, Pages: 6881-6889, ISSN: 0022-0957
Alamar MC, Anastasiadi M, Lopez-Cobollo R, et al., 2020, Transcriptome and phytohormone changes associated with ethylene-induced onion bulb dormancy, Postharvest Biology and Technology, Vol: 168, Pages: 1-13, ISSN: 0925-5214
Control of dormancy and sprouting in onion bulbs is commercially important for postharvest management. Although ethylene application is sometimes used to extend dormancy, the underlying mechanisms regulating dormancy transition remain unclear. Since the sprout leaves emerge from the bulb baseplate, we used this tissue to assess the impact of ethylene treatment and storage time on the hormone profile and the transcriptome. Reads from 30 libraries were assembled and annotated, with 94,840 unigenes retained after filtering. The de novo transcriptome assembly was of high quality and continuity (N50: 1809 bp, GC content: 36.21 %), and was used to analyse differential expression and Gene Onotologies. Across two years, applied ethylene resulted in delayed dormancy break and reduced post-dormancy sprout vigour. Ethylene supplementation enhanced endogenous ethylene production and caused a transient climacteric-like increase in respiration. Significant changes in hormone and associated transcript profiles occurred through storage and in response to ethylene. In particular, abscisic acid (ABA) and its metabolite phaseic acid (PA) increased under ethylene during the longer dormancy period; however, cytokinin increases observed during storage appeared largely independent of ethylene treatment. Several hormone-related transcripts showed differential expression over time and/or in response to ethylene. Expression of ethylene biosynthesis (ACO), receptor (EIN4) and transcription factor (EIL3) genes were modified by ethylene, as were ABA biosynthesis genes such NCED, and cytokinin biosynthesis genes such as LOG and CKX. We conclude that ethylene substantially modifies expression of genes in several phytohormone pathways, and some of these changes may underlie the dormancy-extending effects of exogenous ethylene.
Antoniadi I, Novák O, Gelová Z, et al., 2020, Cell-surface receptors enable perception of extracellular cytokinins, Nature Communications, Vol: 11, Pages: 1-10, ISSN: 2041-1723
Cytokinins are mobile multifunctional plant hormones with roles in development and stress resilience. Although their Histidine Kinase receptors are substantially localised to the endoplasmic reticulum, cellular sites of cytokinin perception and importance of spatially heterogeneous cytokinin distribution continue to be debated. Here we show that cytokinin perception by plasma membrane receptors is an effective additional path for cytokinin response. Readout from a Two Component Signalling cytokinin-specific reporter (TCSn::GFP) closely matches intracellular cytokinin content in roots, yet we also find cytokinins in extracellular fluid, potentially enabling action at the cell surface. Cytokinins covalently linked to beads that could not pass the plasma membrane increased expression of both TCSn::GFP and Cytokinin Response Factors. Super-resolution microscopy of GFP-labelled receptors and diminished TCSn::GFP response to immobilised cytokinins in cytokinin receptor mutants, further indicate that receptors can function at the cell surface. We argue that dual intracellular and surface locations may augment flexibility of cytokinin responses.
Aphids are the economically most important sap‐sucking insect pest worldwide, causing yield losses by draining nutrients from the phloem sap and vectoring viruses. While no genetic resistance to aphids exists in the model plant Arabidopsis thalia, Medicago truncatula has genetic resistance to a range of different aphid species. Over the last decade M. truncatula has thus been used as an excellent model plant to study plant aphid interactions. This book chapter provides an overview on the current major resistance genes and quantitative trait loci (QTLs) that have been identified and the underlying molecular defense responses.
Altmann S, Lopez-Cobollo RM, Thorpe P, et al., 2019, Uncovering the molecular basis of virulence and avirulence in the Medicago - pea aphid system, 18th Congress of International-Society-for-Molecular-Plant-Microbe-Interactions (IS-MPMI), Publisher: AMER PHYTOPATHOLOGICAL SOC, Pages: 151-151, ISSN: 0894-0282
Papadopulos AST, Igea J, Dunning LT, et al., 2019, Ecological speciation in sympatric palms: 3. Genetic map reveals genomic islands underlying species divergence in Howea, Evolution, Vol: 73, Pages: 1986-1995, ISSN: 0014-3820
Although it is now widely accepted that speciation can occur in the face of continuous gene flow, with little or no spatial separation, the mechanisms and genomic architectures that permit such divergence are still debated. Here, we examined speciation in the face of gene flow in the Howea palms of Lord Howe Island, Australia. We built a genetic map using a novel method applicable to long-lived tree species, combining it with double digest restriction-site associated DNA sequencing of multiple individuals. Based upon various metrics, we detected 46 highly differentiated regions throughout the genome, four of which contained genes with functions that are particularly relevant to the speciation scenario for Howea, specifically salt and drought tolerance.
Osborne OG, Ciezarek A, Wilson T, et al., 2019, Speciation in Howea palms occurred in sympatry, was preceded by ancestral admixture, and was associated with edaphic and phenological adaptation, Molecular Biology and Evolution, Vol: 36, Pages: 2682-2697, ISSN: 1537-1719
Howea palms are viewed as one of the most clear-cut cases of speciation in sympatry. The sister species H. belmoreana and H. forsteriana are endemic to the oceanic Lord Howe Island, Australia, where they have overlapping distributions and are reproductively isolated mainly by flowering time differences. However, the potential role of introgression from Australian mainland relatives had not previously been investigated, a process that has recently put other examples of sympatric speciation into question. Furthermore, the drivers of flowering time-based reproductive isolation remain unclear. We sequenced an RNA-seq dataset that comprehensively sampled Howea and their closest mainland relatives (Linospadix, Laccospadix), and collected detailed soil chemistry data on Lord Howe Island to evaluate whether secondary gene flow had taken place and to examine the role of soil preference in speciation. D-statistics analyses strongly support a scenario whereby ancestral Howea hybridised frequently with its mainland relatives, but this only occurred prior to speciation. Expression analysis, population genetic and phylogenetic tests of selection, identified several flowering time genes with evidence of adaptive divergence between the Howea species. We found expression plasticity in flowering time genes in response to soil chemistry as well as adaptive expression and sequence divergence in genes pleiotropically linked to soil adaptation and flowering time. Ancestral hybridisation may have provided the genetic diversity that promoted their subsequent adaptive divergence and speciation, a process that may be common for rapid ecological speciation.
Morris WL, Alamar MC, Lopez-Cobollo RM, et al., 2019, A member of the TERMINAL FLOWER1/CENTRORADIALIS gene family controls sprout growth in potato tubers, Journal of Experimental Botany, Vol: 70, Pages: 835-843, ISSN: 0022-0957
Potato tuber bud dormancy break followed by premature sprouting is a major commercial problem which results in quality losses and decreased tuber marketability. An approach to controlling premature tuber sprouting is to develop potato cultivars with a longer dormancy period and/or reduced rate of sprout growth. Our recent studies using a potato diploid population have identified several QTLs that are associated with tuber sprout growth. In the current study we aim to characterise a candidate gene associated with one of the largest effect QTL for rapid tuber sprout growth on potato chromosome 3. Underlying this QTL is a gene encoding a TERMINAL FLOWER 1/ CENTRORADIALIS homologue (PGSC0003DMG400014322). Here we use a transgenic approach to manipulate the expression level of the CEN family member in a potato tetraploid genotype (cv. Désirée). We demonstrate a clear effect of StCEN expression manipulation, with decreased expression levels associated with an increased rate of sprout growth, and over-expressing lines showing a lower rate of sprout growth than controls. Associated with different levels of StCEN expression were different levels of ABA and cytokinins implying a role in controlling the levels of plant growth regulators in the apical meristem.
Landrein B, Formosa-Jordan P, Malivert A, et al., 2018, Nitrate modulates stem cell dynamics in Arabidopsis shoot meristems through cytokinins, Proceedings of the National Academy of Sciences of the United States of America, Vol: 115, Pages: 1382-1387, ISSN: 0027-8424
The shoot apical meristem (SAM) is responsible for the generation of all the aerial parts of plants. Given its critical role, dynamical changes in SAM activity should play a central role in the adaptation of plant architecture to the environment. Using quantitative microscopy, grafting experiments, and genetic perturbations, we connect the plant environment to the SAM by describing the molecular mechanism by which cytokinins signal the level of nutrient availability to the SAM. We show that a systemic signal of cytokinin precursors mediates the adaptation of SAM size and organogenesis rate to the availability of mineral nutrients by modulating the expression of WUSCHEL, a key regulator of stem cell homeostasis. In time-lapse experiments, we further show that this mechanism allows meristems to adapt to rapid changes in nitrate concentration, and thereby modulate their rate of organ production to the availability of mineral nutrients within a few days. Our work sheds light on the role of the stem cell regulatory network by showing that it not only maintains meristem homeostasis but also allows plants to adapt to rapid changes in the environment.
Herraiz A, Stokes L, Turnbull C, et al., 2018, Developing a new variety of kentia palms (Howea forsteriana): up-regulation of cytochrome b561 and chalcone synthase is associated with the red coloration of the stems, Botany Letters, Vol: 165, Pages: 241-247, ISSN: 2381-8115
The kentia palm (Howea forsteriana) is endemic to a 12 km2 volcanic island in the Tasman Sea, Lord Howe Island. It is one of the most traded houseplants in the world. The typical kentia palm presents a dark green-coloured stem. Note that the stem is made of leaf rachis and petioles, which are intermingled towards the base. However, we discovered on Lord Howe Island a new biological variety that has a red stem. Red-stemmed palm species are known and highly demanded as decorative plants. However, these red palm horticultural varieties require tropical or subtropical conditions to grow, hence commercialization is limited. Thus, a red-stemmed variety of H. forsteriana may have tremendous market potential. Nonetheless, palm trees grow generally slowly and often reach maturity at 15–20 years old or later, which may make conventional strategies unsuitable for the propagation of a new variety. This difficulty needs to be addressed before commercialization can be achieved. Here, we found that anthocyanin is responsible for the red colouration of the stem in the new variety. Using RNA sequencing and quantitative PCR, we identified two gene isoforms displaying altered expression associated with this red colouration, encoding a cytochrome b561 and a chalcone synthase. The latter protein is known to be part of the anthocyanin biosynthesis pathway, which plays a central role in pigmentation in plants. The levels of cytochrome b561 transcripts accumulated were found to be well correlated with an increased anthocyanin concentration in the red stems.
Osborne OG, De-Kayne R, Bidartondo MI, et al., 2017, Arbuscular mycorrhizal fungi promote coexistence and niche divergence of sympatric palm species on a remote oceanic island, New Phytologist, Vol: 217, Pages: 1254-1266, ISSN: 0028-646X
Microbes can have profound effects on their hosts, driving natural selection, promoting speciation and determining species distributions. However, soil-dwelling microbes are rarely investigated as drivers of evolutionary change in plants.We used metabarcoding and experimental manipulation of soil microbiomes to investigate the impact of soil and root microbes in a well-known case of sympatric speciation, the Howea palms of Lord Howe Island (Australia). Whereas H. forsteriana can grow on both calcareous and volcanic soils, H. belmoreana is restricted to, but more successful on, volcanic soil, indicating a trade-off in adaptation to the two soil types.We suggest a novel explanation for this trade-off. Arbuscular mycorrhizal fungi (AMF) are significantly depleted in H. forsteriana on volcanic soil, relative to both H. belmoreana on volcanic soil and H. forsteriana on calcareous soil. This is mirrored by the results of survival experiments, where the sterilization of natural soil reduces Howea fitness in every soil–species combination except H. forsteriana on volcanic soil. Furthermore, AMF-associated genes exhibit evidence of divergent selection between Howea species.These results show a mechanism by which divergent adaptation can have knock-on effects on host–microbe interactions, thereby reducing interspecific competition and promoting the coexistence of plant sister species.
Kanvil S, Pham J, Lopez-Cobollo R, et al., 2017, Cucurbit extrafascicular phloem has strong negative impacts on aphids and is not a preferred feeding site., Plant, Cell and Environment, Vol: 40, Pages: 2780-2789, ISSN: 0140-7791
Cucurbits have long been known to possess two types of phloem: fascicular (FP) within vascular bundles and extrafascicular phloem (EFP) surrounding vascular bundles and scattered through the cortex. Recently, their divergent composition was revealed, with FP having high sugar content consistent with conventional phloem, but EFP having much lower sugar levels and a very different proteome. However, the evolutionary advantages of possessing both FP and EFP have remained unclear. Here, we present four lines of quantitative evidence that together support the hypothesis that FP represents a typical phloem and is an attractive diet for aphids, whereas aphids avoid feeding on EFP. First, aphid stylet track endings were more abundant near the abaxial FP element of minor veins, suggesting a feeding preference for FP over EFP. Second, sugar profiles from stylet exudates were wholly consistent with FP origins, further supporting preference for FP and avoidance of EFP. Third, supplementation of EFP exudate into artificial diets confirmed an aversion to EFP in choice experiments. Finally, EFP exudate had negative effects on aphid performance. On the basis of aphids' inability to thrive on EFP, we conclude that EFP is atypical and perhaps should not be classed as a phloem system.
Barlow NE, Smpokou E, Friddin MS, et al., 2017, Engineering plant membranes using droplet interface bilayers, Biomicrofluidics, Vol: 11, ISSN: 1932-1058
Droplet interface bilayers (DIBs) have become widely recognised as a robust platform for constructing model membranes and are emerging as a key technology for the bottom-up assembly of synthetic cell-like and tissue-like structures. DIBs are formed when lipid-monolayer coated water droplets are brought together inside a well of oil, which is excluded from the interface as the DIB forms. The unique features of the system, compared to traditional approaches (e.g., supported lipid bilayers, black lipid membranes, and liposomes), is the ability to engineer multi-layered bilayer networks by connecting multiple droplets together in 3D, and the capability to impart bilayer asymmetry freely within these droplet architectures by supplying droplets with different lipids. Yet despite these achievements, one potential limitation of the technology is that DIBs formed from biologically relevant components have not been well studied. This could limit the reach of the platform to biological systems where bilayer composition and asymmetry are understood to play a key role. Herein, we address this issue by reporting the assembly of asymmetric DIBs designed to replicate the plasma membrane compositions of three different plant species; Arabidopsis thaliana, tobacco, and oats, by engineering vesicles with different amounts of plant phospholipids, sterols and cerebrosides for the first time. We show that vesicles made from our plant lipid formulations are stable and can be used to assemble asymmetric plant DIBs. We verify this using a bilayer permeation assay, from which we extract values for absolute effective bilayer permeation and bilayer stability. Our results confirm that stable DIBs can be assembled from our plant membrane mimics and could lead to new approaches for assembling model systems to study membrane translocation and to screen new agrochemicals in plants.
de Saint Germain A, Clavé G, Badet-Denisot MA, et al., 2016, An histidine covalent receptor and butenolide complex mediates strigolactone perception, Nature Chemical Biology, Vol: 12, Pages: 787-794, ISSN: 1552-4469
Strigolactone plant hormones control plant architecture and are key players in both symbiotic and parasitic interactions. They contain an ABC tricyclic lactone connected to a butenolide group, the D ring. The DWARF14 (D14) strigolactone receptor belongs to the superfamily of α/β-hydrolases, and is known to hydrolyze the bond between the ABC lactone and the D ring. Here we characterized the binding and catalytic functions of RAMOSUS3 (RMS3), the pea (Pisum sativum) ortholog of rice (Oryza sativa) D14 strigolactone receptor. Using new profluorescent probes with strigolactone-like bioactivity, we found that RMS3 acts as a single-turnover enzyme that explains its apparent low enzymatic rate. We demonstrated the formation of a covalent RMS3-D-ring complex, essential for bioactivity, in which the D ring was attached to histidine 247 of the catalytic triad. These results reveal an undescribed mechanism of plant hormone reception in which the receptor performs an irreversible enzymatic reaction to generate its own ligand.
Lopez-Cobollo RM, Filippis I, Bennett MH, et al., 2016, Comparative proteomics of cucurbit phloem indicates both unique and shared sets of proteins, The Plant Journal, Vol: 88, Pages: 633-647, ISSN: 1365-313X
Cucurbits are well studied phloem biology models but unusually possess both fascicular phloem (FP) within vascular bundles and additional extrafascicular phloem (EFP). Although the functional differences between the two systems are not yet clear, sugar analysis and limited protein profiling previously established that FP and EFP have divergent composition. Here we report a detailed comparative proteomics study of FP and EFP in two cucurbits, pumpkin and cucumber. We re-examined the sites of exudation by video microscopy, and confirmed that in both species, the spontaneous exudate following tissue cutting derives almost exclusively from EFP. Comparative gel electrophoresis and mass spectrometry-based proteomics of exudates, sieve element contents and microdissected stem tissues established that EFP and FP profiles are highly dissimilar, and that there are also species differences. Searches against cucurbit databases enabled identification of more than 300 FP proteins from each species. Few of the detected proteins (~10%) were shared between sieve element contents of FP and EFP, and enriched Gene Ontology categories also differed. To explore quantitative differences in the proteomes, we developed multiple reaction monitoring methods for cucumber proteins that are representative markers for FP or EFP and assessed exudate composition at different times after tissue cutting. Based on failure to detect FP markers in exudate samples, we conclude that FP is blocked very rapidly and therefore contributes minimally to the exudates. Overall, the highly divergent contents of FP and EFP indicate that they are substantially independent vascular compartments. This article is protected by copyright. All rights reserved.
Dunning LT, Hipperson H, Baker WJ, et al., 2016, Ecological speciation in sympatric palms: 1. Gene expression, selection and pleiotropy, Journal of Evolutionary Biology, Vol: 29, Pages: 1472-1487, ISSN: 1420-9101
Ecological speciation requires divergent selection, reproductive isolation, and a genetic mechanism to link the two. We examined the role of gene expression and coding sequence evolution in this process using two species of Howea palms that have diverged sympatrically on Lord Howe Island, Australia. These palms are associated with distinct soil types and have displaced flowering times, representing an ideal candidate for ecological speciation. We generated large amounts of RNA-Seq data from multiple individuals and tissue types collected on the island from each of the two species. We found that differentially expressed loci as well as those with divergent coding sequences between Howea species were associated with known ecological and phenotypic differences, including response to salinity, drought, pH and flowering time. We identified loci with potential dual function in flowering time and soil adaptation, which effect on flowering time was validated by knocking orthologous genes in a model plant species. These results indicate that pleiotropy could have favoured the evolution of barrier traits in this system, despite ongoing gene flow.
Larrieu A, Champion A, Legrand J, et al., 2016, Corrigendum: A fluorescent hormone biosensor reveals the dynamics of jasmonate signalling in plants, Nature Communications, Vol: 7, ISSN: 2041-1723
Antoniadi I, Plackova L, Simonovik B, et al., 2015, Cell-Type-Specific Cytokinin Distribution within the Arabidopsis Primary Root Apex, PLANT CELL, Vol: 27, Pages: 1955-1967, ISSN: 1040-4651
Kanvil S, Collins CM, Powell G, et al., 2015, Cryptic Virulence and Avirulence Alleles Revealed by Controlled Sexual Recombination in Pea Aphids, GENETICS, Vol: 199, Pages: 581-593, ISSN: 0016-6731
Larrieu A, Champion A, Legrand J, et al., 2015, A fluorescent hormone biosensor reveals the dynamics of jasmonate signalling in plants, Nature Communications, Vol: 6, ISSN: 2041-1723
Activated forms of jasmonic acid (JA) are central signals coordinating plant responses to stresses, yet tools to analyse their spatial and temporal distribution are lacking. Here we describe a JA perception biosensor termed Jas9-VENUS that allows the quantification of dynamic changes in JA distribution in response to stress with high spatiotemporal sensitivity. We show that Jas9-VENUS abundance is dependent on bioactive JA isoforms, the COI1 co-receptor, a functional Jas motif and proteasome activity. We demonstrate the utility of Jas9-VENUS to analyse responses to JA in planta at a cellular scale, both quantitatively and dynamically. This included using Jas9-VENUS to determine the cotyledon-to-root JA signal velocities on wounding, revealing two distinct phases of JA activity in the root. Our results demonstrate the value of developing quantitative sensors such as Jas9-VENUS to provide high-resolution spatiotemporal data about hormone distribution in response to plant abiotic and biotic stresses.
Kanvil S, Powell G, Turnbull C, 2014, Pea aphid biotype performance on diverse Medicago host genotypes indicates highly specific virulence and resistance functions, Bulletin of Entomological Research, Vol: 104, Pages: 689-701, ISSN: 1475-2670
Aphid–plant interactions depend on genotypes of both organisms, which determine the two-way molecular exchange that leads to compatible or incompatible outcomes. The underlying genes are mostly unknown, making it difficult to predict likelihood of aphid success or host resistance, and hampering crop genetic improvement. Here we screened eight pea aphid clonal genotypes collected from diverse legume hosts, on a species-wide panel of Medicago truncatula (Mt) genotypes. Aphid virulence was measured by survival, fecundity and growth rate, together with scores for chlorosis and necrosis as host response indicators. Outcomes were highly dependent on the specific aphid–host genotype combinations. Only one Mt line was fully resistant against all clones. Aphid-induced host chlorosis and necrosis varied greatly, but correlated with resistance only in a few combinations. Bi-clustering analysis indicated that all aphid clones could be distinguished by their performance profiles across the host genotypes tested, with each clone being genetically differentiated and potentially representing a distinct biotype. Clones originating from Medicago sativa ranged from highly virulent to almost completely avirulent on both Medicago species, indicating that some were well adapted, whereas others were most likely migrants. Comparisons of closely related pairs of Australian Mt genotypes differing in aphid resistance revealed no enhanced resistance to European pea aphid clones. Based on the extensive variation in pea aphid adaptation even on unfamiliar hosts, most likely reflecting multiple biotype-specific gene-for-gene interactions, we conclude that robust defences require an arsenal of appropriate resistance genes.
Young NF, Ferguson BJ, Antoniadi I, et al., 2014, Conditional Auxin Response and Differential Cytokinin Profiles in Shoot Branching Mutants., Plant physiology, Vol: 165, Pages: 1723-1736, ISSN: 0032-0889
Strigolactone (SL), auxin, and cytokinin (CK) are hormones that interact to regulate shoot branching. For example, several ramosus (rms) branching mutants in pea (Pisum sativum) have SL defects, perturbed xylem CK levels, and diminished responses to auxin in shoot decapitation assays. In contrast with the last of these characteristics, we discovered that buds on isolated nodes (explants) of rms plants instead respond normally to auxin. We hypothesized that the presence or absence of attached roots would result in transcriptional and hormonal differences in buds and subtending stem tissues, and might underlie the differential auxin response. However, decapitated plants and explants both showed similar up-regulation of CK biosynthesis genes, increased CK levels, and down-regulation of auxin transport genes. Moreover, auxin application counteracted these trends, regardless of the effectiveness of auxin at inhibiting bud growth. Multivariate analysis revealed that stem transcript and CK changes were largely associated with decapitation and/or root removal and auxin response, whereas bud transcript profiles related more to SL defects. CK clustering profiles were indicative of additional zeatin-type CKs in decapitated stems being supplied by roots and thus promoting bud growth in SL-deficient genotypes even in the presence of added auxin. This difference in CK content may explain why rms buds on explants respond better to auxin than those on decapitated plants. We further conclude that rapid changes in CK status in stems are auxin dependent but largely SL independent, suggesting a model in which auxin and CK are dominant regulators of decapitation-induced branching, whereas SLs are more important in intact plants.
Grafting provides a simple way to generate chimeric plants with regions of different genotypes and thus to assess the cell autonomy of gene action. The technique of grafting has been widely used in other species, but in Arabidopsis, its small size makes the process rather more demanding. However, there are now several well-established grafting procedures available, which we described here, and their use has already contributed greatly to understanding of such processes as shoot branching control, flowering, disease resistance, and systemic silencing.
Bromley JR, Warnes BJ, Newell CA, et al., 2013, A purine nucleoside phosphorylase in Solanum tuberosum L. (potato) with specificity for cytokinins contributes to the duration of tuber endodormancy, Biochemical Journal, Vol: 458, Pages: 225-237, ISSN: 1470-8728
Solanum tuberosum Cytokinin Riboside Phosphorylase (StCKP1), catalyses the interconversion of the N9-riboside form of the plant hormone cytokinin (CK), a subset of purines, with its most active free base form. StCKP1 prefers CK to unsubstituted aminopurines. The protein was discovered as CK-binding activity in extracts of tuberising potato stolon tips, from which it was isolated by affinity chromatography. The N-terminal amino acid sequence matched the translation product of a set of ESTs, enabling a complete mRNA sequence to be obtained by RACE-PCR. The predicted polypeptide includes a cleavable signal peptide, and motifs for purine nucleoside phosphorylase activity. Expressed protein was assayed for purine nucleoside phosphorylase activity against CKs and adenine/adenosine. Isopentenyladenine, trans-zeatin, dihydrozeatin and adenine were converted to ribosides in the presence of ribose 1-phosphate. In the opposite direction, isopentenyladenosine, trans-zeatin riboside, dihydrozeatin riboside and adenosine were converted to their free bases in the presence of Pi. StCKP1 had no detectable ribohydrolase activity. Evidence is presented that StCKP1 is active in tubers as a negative regulator of CKs, prolonging endodormancy by a chill-reversible mechanism.
Turnbull CGN, Lopez-Cobollo RM, 2013, Heavy traffic in the fast lane: long-distance signalling by macromolecules, NEW PHYTOLOGIST, Vol: 198, Pages: 33-51, ISSN: 0028-646X
Littlewood J, Wang L, Turnbull C, et al., 2013, Techno-economic potential of bioethanol from bamboo in China, Biotechnology for Biofuels, Vol: 6, Pages: 173-173, ISSN: 1754-6834
BACKGROUND:Bamboo is potentially an interesting feedstock for advanced bioethanol production in China due to its natural abundance, rapid growth, perennial nature and low management requirements. Liquid hot water (LHW) pretreatment was selected as a promising technology to enhance sugar release from bamboo lignocellulose whilst keeping economic and environmental costs to a minimum. The present research was conducted to assess: 1) by how much LHW pretreatment can enhance sugar yields in bamboo, and 2) whether this process has the potential to be economically feasible for biofuel use at the commercial scale. Pretreatments were performed at temperatures of 170-190?C for 10?30 minutes, followed by enzymatic saccharification with a commercial enzyme cocktail at various loadings. These data were then used as inputs to a techno-economic model using AspenPlus? to determine the production cost of bioethanol from bamboo in China.RESULTS:At the selected LHW pretreatment of 190?C for 10 minutes, 69% of the initial sugars were released under a standardised enzyme loading; this varied between 59-76% when 10?140 FPU/g glucan of commercial enzyme Cellic CTec2 was applied. Although the lowest enzyme loading yielded the least amount of bioethanol, the techno-economic evaluation revealed it to be the most economically viable scenario with a production cost of $0.484 per litre (with tax exemption and a $0.16/litre subsidy). The supply-chain analysis demonstrated that bioethanol could be economically competitive with petrol at the pump at enzyme loadings up to 60 FPU/g glucan. However, in a prospective scenario with reduced government support, this enzyme loading threshold would be reduced to 30 FPU/g glucan.CONCLUSIONS:Bioethanol from bamboo is shown to be both technically and economically feasible, as well as competitive with petrol in China. Alternative approaches to reduce bioethanol production costs are still needed however, to ensure its competitiveness in a possible future scenar
Hardner CM, Peace C, Vithanage V, et al., 2012, Genetic Resources and Improvement in Macadamia, 1st International Symposium on Wild Relatives of Subtropical and Temperate Fruit and Nut Crops, Publisher: INT SOC HORTICULTURAL SCIENCE, Pages: 253-262, ISSN: 0567-7572
Braun N, de Saint Germain A, Pillot J-P, et al., 2011, The pea TCP transcription factor PsBRC1 acts downstream of strigolactones to control shoot branching, Plant Physiology, Vol: 158, Pages: 225-238, ISSN: 1532-2548
The function of PsBRC1, the pea (Pisum sativum) homolog of the maize (Zea mays) TEOSINTE BRANCHED1 and the Arabidopsis (Arabidopsis thaliana) BRANCHED1 (AtBRC1) genes, was investigated. The pea Psbrc1 mutant displays an increased shoot-branching phenotype, is able to synthesize strigolactone (SL), and does not respond to SL application. The level of pleiotropy of the SL-deficient ramosus1 (rms1) mutant is higher than in the Psbrc1 mutant, rms1 exhibiting a relatively dwarf phenotype and more extensive branching at upper nodes. The PsBRC1 gene is mostly expressed in the axillary bud and is transcriptionally up-regulated by direct application of the synthetic SL GR24 and down-regulated by the cytokinin (CK) 6-benzylaminopurine. The results suggest that PsBRC1 may have a role in integrating SL and CK signals and that SLs act directly within the bud to regulate its outgrowth. However, the Psbrc1 mutant responds to 6-benzylaminopurine application and decapitation by increasing axillary bud length, implicating a PsBRC1-independent component of the CK response in sustained bud growth. In contrast to other SL-related mutants, the Psbrc1 mutation does not cause a decrease in the CK zeatin riboside in the xylem sap or a strong increase in RMS1 transcript levels, suggesting that the RMS2-dependent feedback is not activated in this mutant. Surprisingly, the double rms1 Psbrc1 mutant displays a strong increase in numbers of branches at cotyledonary nodes, whereas branching at upper nodes is not significantly higher than the branching in rms1. This phenotype indicates a localized regulation of branching at these nodes specific to pea.
Turnbull C, 2011, Long-distance regulation of flowering time, JOURNAL OF EXPERIMENTAL BOTANY, Vol: 62, Pages: 4399-4413, ISSN: 0022-0957
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