Project description:Vegetative phase change is the developmental transition from the juvenile phase to the adult phase during which a plant becomes competent for sexual reproduction. Gain of ability to flower is often accompanied by changes in patterns of differentiation in newly forming vegetative organs. In maize, juvenile leaves differ from adult leaves in morphology, anatomy, and cell wall composition. Whereas the normal sequence of juvenile followed by adult is repeated with every sexual generation, this sequence can be altered in maize by the isolation and culture of the shoot apex from an adult phase plant; an “adult” meristem so treated reverts to forming juvenile vegetative organs. To investigate the molecular differences between the juvenile and adult phases in maize comparisons among two juvenile samples, leaf 4 and culture-derived leaf 3 or 4, and an adult sample (leaf 9) were made using cDNA microarrays. All samples were leaf primordia at plastochron 6. A gene was scored as “phase specific” if it was up- (or down-) regulated in both juvenile samples compared to the adult sample with at least a twofold-change in gene expression at P-value less than or equal to 0.005. Some 221 ESTs up-regulated in juvenile and 28 ESTs up-regulated in adult were identified. Altered patterns of expression of selected ESTs in the phase change mutants Tp2, d1 and gl15 further confirmed these genes as being phase-specific and allowed us to position these genes in the known genetic hierarchy regulating phase change. Keywords: Transcript profiling among seed-derived juvenile leaf 4 and adult leaf 9 and culture-rejuvenated leaf 3 or 4 in maize
Project description:In plants, juvenile to adult phase transition is regulated by the sequential activity of two microRNAs: miR156 and miR172. A decline in miR156 and increase in miR172 abundance is associated with phase transition. There is very limited information on phase transition in economically important horticultural tree crops, which have a significantly long vegetative phase affecting fruit bearing. Here we profiled various molecular cues known to be involved in phase transition and flowering, including the microRNAs miR156 and miR172, in three horticultural tree crops avocado (Persea americana), mango (Mangifera indica) and macadamia (Macadamia integrifolia). We observed that miR156 expression decreases as these trees age and can potentially be used as a juvenility marker. Consistent with findings in annual plants, we also observed conserved regulation of the miR156-SPL3/4/5 regulatory module in these genetically distant tree crops, suggesting that this pathway may play a highly conserved role in vegetative identity. Meanwhile, the abundance of miR172 and its target AP2-like genes, as well as the accumulation level of SPL9 transcripts, were not related with plant age in these crops except in avocado where miR172 expression increased steadily. Finally, we demonstrate that various floral genes, including AP1 and SOC1 were upregulated in the reproductive phase and can be used as potential markers for the reproductive phase transition. Overall, this study provides an insight into the molecular associations of juvenility and phase transition in horticultural trees where crop breeding and improvement is encumbered by long juvenile phases.
Project description:Vegetative phase change is the developmental transition from the juvenile phase to the adult phase during which a plant becomes competent for sexual reproduction. Gain of ability to flower is often accompanied by changes in patterns of differentiation in newly forming vegetative organs. In maize, juvenile leaves differ from adult leaves in morphology, anatomy, and cell wall composition. Whereas the normal sequence of juvenile followed by adult is repeated with every sexual generation, this sequence can be altered in maize by the isolation and culture of the shoot apex from an adult phase plant; an âadultâ meristem so treated reverts to forming juvenile vegetative organs. To investigate the molecular differences between the juvenile and adult phases in maize comparisons among two juvenile samples, leaf 4 and culture-derived leaf 3 or 4, and an adult sample (leaf 9) were made using cDNA microarrays. All samples were leaf primordia at plastochron 6. A gene was scored as âphase specificâ if it was up- (or down-) regulated in both juvenile samples compared to the adult sample with at least a twofold-change in gene expression at P-value less than or equal to 0.005. Some 221 ESTs up-regulated in juvenile and 28 ESTs up-regulated in adult were identified. Altered patterns of expression of selected ESTs in the phase change mutants Tp2, d1 and gl15 further confirmed these genes as being phase-specific and allowed us to position these genes in the known genetic hierarchy regulating phase change. Keywords: Transcript profiling among seed-derived juvenile leaf 4 and adult leaf 9 and culture-rejuvenated leaf 3 or 4 in maize To identify juvenile or adult specific ESTs, total RNA from leaf primordia at plastochron 6 (P6) was isolated from leaves 4 (L4) and 9 (L9) from seed-derived plants and leaf 3 or 4 (RL3/4) from culture-derived plants. For each of six biological replications, each of the three pairwise comparisons of P6-staged leaf primordia from L4, L9 and RL3/4 was made on one slide. With six biological replications and three slides per replication (L4 vs. L9, L9 vs. RL3/4, RL3/4 vs. L4), this replicated loop design used a total of 18 slides. To ensure dye balance, each of the 18 target samples was measured once with Cy3 labeling and once with Cy5 labeling.
Project description:As maize (Zea mays) plants undergo vegetative phase change from juvenile to adult, they both exhibit heteroblasty, an abrupt change in patterns of leaf morphogenesis, and gain the ability to produce flowers. Both processes are under the control of microRNA 156, whose levels decline at the end of the juvenile phase. Gain of ability to flower is conferred by expression of miR156 targets that encode Squamosa Promoter-Binding (SBP) transcription factors, which when derepressed in the adult phase induce the expression of MADS-box transcription factors that promote maturation and flowering. What gene expression differences underlie heteroblasty, as well as what regulates miR156 levels, remain open questions. Here, we compare gene expression in primordia that will develop into juvenile or adult leaves to identify genes that define these two developmental states and may influence vegetative phase change. In comparisons among successive leaves at the same developmental stage of plastochron 6, three-fourths of approximately 1,100 differentially expressed genes were more highly expressed in primordia of juvenile leaves. This juvenile set was enriched in photosynthetic genes, particularly those associated with cyclic electron flow at photosystem I, and in genes involved in oxidative stress and retrograde redox signaling. Pathogen- and herbivory-responsive pathways including jasmonic acid and salicylic acid were also up-regulated in juvenile primordia and indeed, exogenous application of jasmonic acid both delayed the appearance of adult traits and the decline of miR156 levels in maize seedlings. The successful amelioration of stress signals thus plays an important role in inducing vegetative phase change in maize.
Project description:As maize (Zea mays) plants undergo vegetative phase change from juvenile to adult, they both exhibit heteroblasty, an abrupt change in patterns of leaf morphogenesis, and gain the ability to produce flowers. Both processes are under the control of microRNA 156, whose levels decline at the end of the juvenile phase. Gain of ability to flower is conferred by expression of miR156 targets that encode Squamosa Promoter-Binding (SBP) transcription factors, which when derepressed in the adult phase induce the expression of MADS-box transcription factors that promote maturation and flowering. What gene expression differences underlie heteroblasty, as well as what regulates miR156 levels, remain open questions. Here, we compare gene expression in primordia that will develop into juvenile or adult leaves to identify genes that define these two developmental states and may influence vegetative phase change. In comparisons among successive leaves at the same developmental stage of plastochron 6, three-fourths of approximately 1,100 differentially expressed genes were more highly expressed in primordia of juvenile leaves. This juvenile set was enriched in photosynthetic genes, particularly those associated with cyclic electron flow at photosystem I, and in genes involved in oxidative stress and retrograde redox signaling. Pathogen- and herbivory-responsive pathways including jasmonic acid and salicylic acid were also up-regulated in juvenile primordia and indeed, exogenous application of jasmonic acid both delayed the appearance of adult traits and the decline of miR156 levels in maize seedlings. The successful amelioration of stress signals thus plays an important role in inducing vegetative phase change in maize. 12 untreated samples (8mm primordia of leaves 1-12) and 1 treated sample (leaf 5 primordium, 15mM JA treatment). 2 or more technical replicates per sample
Project description:Background: A long juvenile period between germination and flowering is a common characteristic among fruit trees, including Malus hupehensis (Pamp.) Rehd., which is an apple rootstock widely used in China. microRNAs (miRNAs) play an important role in the regulation of phase transition and reproductive growth processes. Results: M. hupehensis RNA libraries, one adult and one juvenile phase, were constructed using tree leaves and underwent high-throughput sequencing. We identified 42 known miRNA families and 172 novel miRNAs. We also identified 127 targets for 25 known miRNA families and 168 targets for 35 unique novel miRNAs using degradome sequencing. The identified miRNA targets were categorized into 58 biological processes, and the 123 targets of known miRNAs were associated with phase transition processes. The KEGG analysis revealed that these targets were involved in starch and sucrose metabolism, and plant hormone signal transduction. Expression profiling of miRNAs and their targets indicated multiple regulatory functions in the phase transition. The higher expression level of mdm-miR156 and lower expression level of mdm-miR172 in the juvenile phase leaves implied that these two small miRNAs regulated the phase transition. mdm-miR160 and miRNA393, which regulate genes involved in auxin signal transduction, could also be involved in controlling this process. The identification of known and novel miRNAs and their targets provides new information on this regulatory process in M. hupehensis, which will contribute to the understanding of miRNA functions during growth, phase transition and reproduction in woody fruit trees. Conclusions: A comprehensive study on M. hupehensis miRNAs related to the juvenile to adult phase transition was performed. The combination of sRNA and degradome sequencing can be used to better illustrate the profiling of hormone-regulated miRNAs and miRNA targets involving complex regulatory networks, which will contribute to the understanding of miRNA functions during growth, phase transition and reproductive growth in perennial woody fruit trees.
Project description:In this study we identified the NAC family member VviCARPO (Controlled Adjustment of Ripening and maturation of Plant Organs) as a key regulator of grapevine maturation. We explored CARPO binding landscapes through DAP-seq and overlapped its bound genes with transcriptomics datasets from stable and transient CARPO overexpressing grapevine plants to narrow a set of high-confidence targets. Among these, we identified key molecular ripening markers. Physiological, metabolic and promoter activation analyses showed that CARPO induces chlorophyll degradation and anthocyanin accumulation through the up regulation of VviSGR1 and VviMYBA1, respectively, with the latter being up-regulated by a VviCARPO-VviNAC03 regulatory complex. CARPO complemented the nor mutant phenotype in tomato, suggesting it may have acquired a dual role as an orchestrator of both ripening- and senescence-related processes. Our results evidenced that CARPO is a master regulator of the grapevine vegetative-to-mature phase organ transition and therefore an essential target for insuring fruit quality and environmental resilience.
Project description:In this study we identified the NAC family member VviCARPO (Controlled Adjustment of Ripening and maturation of Plant Organs) as a key regulator of grapevine maturation. We explored CARPO binding landscapes through DAP-seq and overlapped its bound genes with transcriptomics datasets from stable and transient CARPO overexpressing grapevine plants to narrow a set of high-confidence targets. Among these, we identified key molecular ripening markers. Physiological, metabolic and promoter activation analyses showed that CARPO induces chlorophyll degradation and anthocyanin accumulation through the up regulation of VviSGR1 and VviMYBA1, respectively, with the latter being up-regulated by a VviCARPO-VviNAC03 regulatory complex. CARPO complemented the nor mutant phenotype in tomato, suggesting it may have acquired a dual role as an orchestrator of both ripening- and senescence-related processes. Our results evidenced that CARPO is a master regulator of the grapevine vegetative-to-mature phase organ transition and therefore an essential target for insuring fruit quality and environmental resilience.
Project description:Grapevine is a woody temperate perennial plant and one of the most important fruit crops with global relevance in both the fresh fruit and winemaking industries. Unfortunately, global warming is affecting viticulture by altering developmental transitions and fruit maturation processes. In this context, uncovering the molecular mechanisms controlling the onset and progression of ripening could prove essential to maintain high-quality grapes and wines. Through a deep inspection of previously published transcriptomic data we identified the NAC family member VviCARPO (Controlled Adjustment of Ripening and maturation of Plant Organs) as a key regulator of grapevine maturation whose induction precedes the expression of well-known ripening associated genes. We explored VviCARPO binding landscapes through DAP-seq and overlapped its bound genes with transcriptomics datasets from stable and transient VviCARPO overexpressing grapevine plants to define a set of high-confidence targets. Among these, we identified key molecular ripening markers. Physiological, metabolic and promoter activation analyses showed that VviCARPO induces chlorophyll degradation and anthocyanin accumulation through the up-regulation of VviSGR1 and VviMYBA1, respectively, with the latter being up-regulated through a VviCARPO-VviNAC03 regulatory complex. Despite showing a closer phylogenetic relationship to senescent-related AtNAP homologues, VviCARPO complemented the nor mutant phenotype in tomato, suggesting it may have acquired a dual role as an orchestrator of both ripening- and senescence-related processes. Our data supports CARPO as a master regulator of the grapevine vegetative-to-mature phase organ transition and therefore an essential target for insuring fruit quality and environmental resilience.
Project description:The first genome-wide transcriptomic atlas of grapevine (Vitis vinifera) is based on 54 diverse samples expressing ~93% of predicted grapevine genes. Pollen and senescent leaves have unique transcriptomes but microarray analysis grouped all other samples into vegetative/green or mature/woody categories based on maturity rather than organ identity. This fundamental transcriptome reprograming during maturation was highlighted by three distinct statistical approaches supported by gene coexpression analysis. The shift to the mature/woody developmental program results from the reiterative coactivation of pathways that are largely inactive in vegetative/green tissues, often involving the coregulation of neighboring genes and global regulation based on codon preference.