Project description:Leaf size and flatness directly affect photosynthesis and are closely related to agricultural yield. The final leaf size and shape are coordinately determined by cell proliferation, differentiation, and expansion during leaf development. Lettuce (Lactuca sativa L.) is one of the most important leafy vegetables worldwide, and lettuce leaves vary in shape and size. However, the molecular mechanisms of leaf development in lettuce are largely unknown. In this study, we showed that the lettuce APETALA2 (LsAP2) gene regulates leaf morphology. LsAP2 encodes a transcriptional repressor that contains the conserved EAR motif, which mediates interactions with the TOPLESS/TOPLESS-RELATED (TPL/TPR) corepressors. Overexpression of LsAP2 led to small and crinkly leaves, and many bulges were seen on the surface of the leaf blade. LsAP2 physically interacted with the CINCINNATA (CIN)-like TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) transcription factors and inhibited their transcriptional activation activity. RNA sequencing analysis showed that LsAP2 affected the expression of auxin- and polarity-related genes. In addition, LsAP2 directly repressed the abaxial identity gene KANADI2 (LsKAN2). Together, these results indicate that LsAP2 regulates leaf morphology by inhibiting CIN-like TCP transcription factors and repressing LsKAN2, and our work provides insights into the regulatory mechanisms of leaf development in lettuce.
Project description:Mutations in the CINCINNATA gene in Antirrhinum and its orthologues in Arabidopsis cause negative surface curvature in leaves due to excess marginal growth. CIN-like genes code for TCP transcription factors and are expressed in a broad zone of a growing leaf somewhat distal to the proliferation zone. Although a few TCP targets are known, the role of CIN-like TCP genes in regulating leaf curvature has remained unclear. We have compared the global transcription profile of wild type and cincinnata mutant to identify its targets. By combining DNA-protein interaction, chromatin immunoprecipitation and RNA in situ hybridization, we show that CIN maintains surface flatness by regulating signaling or level of major plant hormones. CIN promotes cytokinin signaling directly and GA level indirectly, in accelerating maturity in leaf cells along the tip-to-base direction. In addition, CIN suppresses auxin signaling more at the margin than centre by establishing a margin-to-medial expression gradient of a homologue of the auxin suppressor IAA3. Our results uncover an underlying mechanism in a developing leaf that controls maturity of leaf and its surface curvature. Considering the conservation of CIN-like genes and their function in leaf morphogenesis in multiple plant species, it is likely that such mechanism is evolutionarily conserved.
Project description:Mutations in the CINCINNATA gene in Antirrhinum and its orthologues in Arabidopsis cause negative surface curvature in leaves due to excess marginal growth. CIN-like genes code for TCP transcription factors and are expressed in a broad zone of a growing leaf somewhat distal to the proliferation zone. Although a few TCP targets are known, the role of CIN-like TCP genes in regulating leaf curvature has remained unclear. We have compared the global transcription profile of wild type and cincinnata mutant to identify its targets. By combining DNA-protein interaction, chromatin immunoprecipitation and RNA in situ hybridization, we show that CIN maintains surface flatness by regulating signaling or level of major plant hormones. CIN promotes cytokinin signaling directly and GA level indirectly, in accelerating maturity in leaf cells along the tip-to-base direction. In addition, CIN suppresses auxin signaling more at the margin than centre by establishing a margin-to-medial expression gradient of a homologue of the auxin suppressor IAA3. Our results uncover an underlying mechanism in a developing leaf that controls maturity of leaf and its surface curvature. Considering the conservation of CIN-like genes and their function in leaf morphogenesis in multiple plant species, it is likely that such mechanism is evolutionarily conserved. Two color Experiment, Organism: Arabidopsis thaliana and Antirrhinum. Arrays Used: 1. Agilent Arabidopsis thaliana Gene expression Microarray 22k (AMADID: 013324) 2. Agilent Custom Arabidopsis thaliana 4x44k Gene Expression (AMADID: 015226) 3. Agilent custom Antirrhinum 4x44k Gene expression (AMADID: 016341) designed by Genotypic Technology Private Limited.
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. When calibrated by informative root markers, the same algorithm accurately diagnosed dissected root samples. We used the DDI to characterize plants with reduced activities of multiple CINCINNATA (CIN)-TCP growth regulators. These plants had giant curled leaves made up of small cells with abnormal shape, low DDI scores and low expression of mitosis markers, depicting the primary role of CIN-TCPs as promoters of differentiation. Delayed activity of several CIN-TCPs resulted in abnormally large but flat leaves with regular cells. The application of DDI has therefore portrayed the CIN-TCPs as heterochronic regulators that permit the development of a flexible and robust leaf form through an ordered and protracted maturation schedule. Experiment Overall Design: Vegetative apices of arabidopsis plants from modified CIN-TCP activity were collected. Experiment Overall Design: 1. Overexpression of an artificial microRNA targeting TCP5, TCP13 and TCP17 Experiment Overall Design: 2. Overexpression of the endogenous microRNA 319b targeting TCP2, TCP3, TCP4, TCP10 and TCP24 Experiment Overall Design: 3. the combination of the two microRNA, knocking down the eight CIN-TCP Experiment Overall Design: 4. Overexpression of TCP4 under the leaf specific BLS promoter
Project description:Leaves are flat determinate organs derived from indeterminate shoot apical meristems. The presence of a specific leaf meristem is debated, as anatomical features typical of meristems are not present in leaves. Here we demonstrate that multiple NGATHA (NGA) and CINCINNATA-class-TCP (CIN-TCP) transcription factors act redundantly to suppress activity of a leaf margin meristem in Arabidopsis thaliana, and that their absence confers persistent marginal growth of leaves, cotyledons and floral organs. The marginal meristem is activated by the juxtaposition of adaxial and abaxial domains and maintained by WOX homeobox transcription factors, but other margin elaboration genes are dispensable for its maintenance. This genetic framework parallels the morphogenetic program of shoot apical meristems and may represent a relic from an ancestral shoot system from which seed plant leaves evolved.
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. When calibrated by informative root markers, the same algorithm accurately diagnosed dissected root samples. We used the DDI to characterize plants with reduced activities of multiple CINCINNATA (CIN)-TCP growth regulators. These plants had giant curled leaves made up of small cells with abnormal shape, low DDI scores and low expression of mitosis markers, depicting the primary role of CIN-TCPs as promoters of differentiation. Delayed activity of several CIN-TCPs resulted in abnormally large but flat leaves with regular cells. The application of DDI has therefore portrayed the CIN-TCPs as heterochronic regulators that permit the development of a flexible and robust leaf form through an ordered and protracted maturation schedule.
Project description:Chitin soil amendment is known to improve soil quality, plant growth and plant stress resilience, but the underlying mechanisms are not well understood. In this study, we monitored chitin’s effect on lettuce physiology every two weeks through an eight-week growth period, analyzed the early transcriptional reprogramming and related metabolomic changes of lettuce, in response to crab chitin treatment in peat-based potting soil. In commercial growth conditions, chitin amendment still promoted lettuce growth, increased chlorophyll content, the number of leaves and crop head weight from week six. The flavonoid content in lettuce leaves was altered as well, showing an increase at week two but a decrease from week six. Transcriptomic analysis showed that over 300 genes in lettuce root were significant differentially expressed after chitin soil treatment. Gene Ontology-term (GO) enrichment analysis revealed statistical overrepresentation of GO terms linked to photosynthesis, pigment metabolic process and phenylpropanoid metabolic process. Further analysis of the differentially expressed genes (DEGs) showed that the flavonoid pathway is mostly upregulated whereas the bifurcation of upstream phenylpropanoid pathway towards lignin biosynthesis is mostly downregulated. Metabolomic analysis revealed the upregulation of salicylic acid, chlorogenic acid, ferulic acid, and p-coumaric acid in chitin treated lettuce seedlings. These phenolic compounds mainly influence the phenylpropanoid biosynthesis pathway and may play important roles in plant defense reactions. Our results suggest that chitin soil amendments might activate induced resistance by priming lettuce plants and promote lettuce growth via transcriptional changes.
Project description:Verotoxigenic Escherichia coli (VTEC) are a leading cause of food-borne illness. Fruit and vegetables are recognised as an important source of the pathogen and can account for ~ 25 % of food-borne VTEC outbreaks, globally. The ability of VTEC to colonise leaves and roots of leafy vegetables, spinach (Spinacia oleracea) and lettuce (Lactuca sativa), was compared. The highest levels of colonisation occurred in the roots and rhizosphere, whereas colonisation of the leaves was lower and significantly different between the species. Colonisation of the leaves of prickly lettuce (L. serriola), a wild relative of domesticated lettuce, was especially poor. Differential VTEC gene expression in spinach extracts was markedly different for three tissue types, with little overlap. Comparison of expression in the same tissue type, cell wall polysaccharides, for lettuce and spinach also showed substantial differences, again with virtually no overlap. The transcriptional response was largely dependent on temperatures that are relevant to plant growth, not warm-blooded animals. The data show that VTEC adaptation to plant hosts and subsequent colonisation potential is underpinned by wholescale changes in gene expression that are specific to both plant tissue type and to the species.