Project description:Leaf development has been monitored chiefly by following anatomical markers. Analysis of transcriptome dynamics during leaf maturation revealed multiple expression patterns that rise or fall with age or that display age specific peaks. These were used to formulate a digital differentiation index (DDI), based on a set of selected markers with informative expression during leaf ontogeny. The leaf-based DDI reliably predicted the developmental state of leaf samples from diverse sources and was independent of mitotic cell division transcripts or propensity of the specific cell type. To calibrate and test the DDI a series of Arabidopsis shoot development was used (Efroni et al, 2008)
Project description:Dynamic cell identities underlie flexible developmental programs. The stomatal lineages in the Arabidopsis leaf epidermis feature asynchronous and indeterminate divisions that can be modulated by environmental cues. The products of these lineages, stomatal guard cells and pavement cells, regulate plant-atmosphere exchanges, and the epidermis as a whole influences overall leaf growth. How flexibility is encoded in development of the stomatal lineage, and how cell fates are coordinated in the leaf are open questions. Here, we offer single-cell transcriptomes to uncover models of cell differentiation within Arabidopsis leaf tissue.
Project description:Leaf development has been monitored chiefly by following anatomical markers. Analysis of transcriptome dynamics during leaf maturation revealed multiple expression patterns that rise or fall with age or that display age specific peaks. These were used to formulate a digital differentiation index (DDI), based on a set of selected markers with informative expression during leaf ontogeny. The leaf-based DDI reliably predicted the developmental state of leaf samples from diverse sources and was independent of mitotic cell division transcripts or propensity of the specific cell type. To calibrate and test the DDI a series of Arabidopsis shoot development was used (Efroni et al, 2008) Experiment Overall Design: Four samples from different stages of shoot and leaf development taken from plants grown at short days (10 hours light at 20C), starting from 5 days after sowing (DAS) apices to 35 DAS fully expanded leaves. RNA was hybridized to affymatrix ATH1 arrays and done in duplicates.
Project description:Plants grow continuously and undergo numerous changes in their vegetative morphology and physiology during their life span. The molecular basis of these changes is largely unknown. To provide a more comprehensive picture of shoot development in Arabidopsis, microarray analysis was used to profile the mRNA content of shoot apices of different ages, as well as leaf primordia and fully-expanded leaves from 6 different positions on the shoot, in early-flowering and late-flowering genotypes. This extensive dataset provides a new and unexpectedly complex picture of shoot development in Arabidopsis. At any given time, the pattern of gene expression is different in every leaf on the shoot, and reflects the activity at least 6 developmental programs. Three of these are specific to individual leaves (leaf maturation, leaf aging, leaf senescence), two occur at the level of the shoot apex (vegetative phase change, floral induction), and one involves the entire shoot (shoot aging). Our results demonstrate that vegetative development is a much more dynamic process that previously imagined, and provide new insights into the underlying mechanism of this process.
Project description:Leaf senescence, the last step of leaf development which is important for plant’s fitness, proceeds with age but is modulated by various environmental stresses and hormones. Salt stress is one of the well-known environmental stresses that accelerate leaf senescence. However, the molecular mechanisms how the signal of salt stress is integrated into leaf senescence programs are still elusive. In this study, we characterized the function of an Arabidopsis APETALA 2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) family transcription factor, ERF34, in salt stress-induced leaf senescence. ERF34 was differentially expressed under leaf senescence-inducing conditions including age, dark, and high salt. ERF34 negatively regulated salt stress-induced leaf senescence as well as promoted salt stress tolerance at diverse developmental stages. Analysis of genome-wide targets of ERF34 revealed that the overexpression of ERF34 could alter salt-responsive gene expression. Moreover, ERF34 directly bound to the promoters of EARLY RESPONSIVE TO DEHYDRATION 10 and RESPONSE TO DESICCATION 29A and activated their expression. Our findings imply that ERF34 is a key regulator in the convergence of salt stress response with the regulatory programs of leaf senescence and is a potential candidate for crop improvement, particularly by enhancing salt stress tolerance.
Project description:Leaf senescence is governed by a complex regulatory network involving dynamic reprogramming of gene expression. Recent evidence indicates that trimethylation of histone H3 at lysine 4 (H3K4me3) alters gene expression during leaf senescence. However, it is largely unknown how histone modification is regulated in an age-dependent manner. We found that JMJ16, an Arabidopsis JmjC-domain containing protein, is a specific H3K4 demethylase that negatively regulates leaf senescence. The histone demethylase activity and the JmjN, JmjC, and FYR domains of JMJ16, but not the zf-C5HC2 domain, are essential for JMJ16 function in the regulation of leaf senescence. Genome-wide analysis revealed a widespread coordinated up-regulation of H3K4me3 and gene expression associated with leaf senescence in the loss-of-function jmj16 mutant compared with the wild type. Genetic analysis indicated that JMJ16 negatively regulates leaf senescence at least partly through repressing the expression of WRKY53 and SAG201, two known positive regulators of leaf senescence. Further analyses demonstrated that JMJ16 associates with WRKY53 and SAG201, and represses precocious expression of WRKY53 and SAG201 in mature leaves by reducing H3K4me3 levels at these loci. Moreover, association of JMJ16 on WRKY53 and SAG201 loci increased at mature stage but decreased at later stage, suggesting that the age-dependent dynamic chromatin association of JMJ16 is required for precise transcriptional activation of SAGs during leaf senescence. Thus, JMJ16 is an important regulator of leaf senescence that demethylates H3K4 at senescence-associated genes in an age-dependent manner.