Project description:During de-etiolation of Arabidopsis seedlings, light promotes the expansion of cotyledons but inhibits the elongation of hypocotyls. The mechanism of this differential regulation of cell enlargement is unclear. Our organ-specific transcriptomic analysis identified 32 Small Auxin Up RNA (SAUR) genes whose transcripts were light-induced in cotyledons and/or repressed in hypocotyls. We therefore named these SAURs as lirSAURs. Both overexpression and mutation analyses demonstrated that lirSAURs could promote cotyledon expansion and opening and enhance hypocotyl elongation, possibly by inhibiting phosphatase activity of PP2C-Ds. Light reduced auxin levels to down-regulate the expression of lirSAURs in hypocotyls. Further, phytochrome-interacting factors (PIFs) were shown
Project description:MicroRNAs and phytophormes are all small molecular signals that play important roles in regulating development and environmental responses in plants. The interplay between them allow the plants to better converge multiple inner and outer signals to optimizing their survival strategy. So far, the knowledge of how miRNAs are involved in brassinosteroid (BR) signaling is lacking. Here, we report the finding of miR394 and its target gene LEAF CURLING RESPONSENESS (LCR), which were transcriptionally responsive to BR, participate in BR signaling in regulating hypocotyls elongation in Arabidopsis. By phenotypic analyzing of a set of transgenic and mutants, miR394 was found to act as a negative regulator in BR signaling in hypocotyls elongation, while its target gene on the contrary. Genetically, miR394 functions upstream of BIN2 and BZR1/BES1, but partially downstream or independent with BRI1 and BSU1. RNA-seq analysis further supports that miR394 inhibits BR signaling through BIN2 because miR394 co-regulate significant number of genes together with BIN2. Additionally, miR394 improved the accumulation of BIN2 but decreased the protein amount of BZR1 and BES1, which can be phosphorylated by BIN2. miR394 also repressed the transcription of PRE1/5/6 and EXP8, the key hypocotyls elongation regulating genes, which had been reported to be BZR1/BES1 targets. These findings revealed a new pathway that miRNA involved in BR signaling in Arabidopsis.
Project description:Plants have evolved shoot elongation mechanisms to escape from diverse environmental stresses such as flooding and vegetative shade. The apparent similarity in growth responses suggests possible convergence of the signalling pathways. Shoot elongation is mediated by passive ethylene accumulating in flooded plant organs and by changes in light quality and quantity under vegetation shade. Here we study hypocotyl elongation as a proxy for shoot elongation and delineated Arabidopsis hypocotyl length kinetics in response to ethylene and shade. Based on these kinetics, we further investigated ethylene and shade-induced genome-wide gene expression changes in hypocotyls and cotyledons separately. Both treatments induced a more extensive transcriptome reconfiguration in the hypocotyls compared to the cotyledons. Bioinformatics analyses suggested contrasting regulation of growth promotion- and photosynthesis-related genes. These analyses also suggested an induction of auxin, brassinosteroid and gibberellin signatures and the involvement of several candidate regulators in the elongating hypocotyls. Pharmacological and mutant analyses confirmed the functional involvement of several of these candidate genes and physiological control points in regulating stress-escape responses to different environmental stimuli. We discuss how these signaling networks might be integrated and conclude that plants, when facing different stresses, utilise a conserved set of transcriptionally regulated genes to modulate and fine tune growth. 1 day old Arabidopsis seedlings were subjected to control, ethylene and shade conditions. Hypocotyl and cotyledon tissues were harvested at 1.5 h, 13.5 h and 25.5 h of treatment time respectively. Microarray hybridization was carried out with 3 biological replicates (collected over 3 independent experiments) of each sample using the Affymetrix Arabidopsis Gene 1.1 ST platform.
Project description:Plants have evolved shoot elongation mechanisms to escape from diverse environmental stresses such as flooding and vegetative shade. The apparent similarity in growth responses suggests possible convergence of the signalling pathways. Shoot elongation is mediated by passive ethylene accumulating in flooded plant organs and by changes in light quality and quantity under vegetation shade. Here we study hypocotyl elongation as a proxy for shoot elongation and delineated Arabidopsis hypocotyl length kinetics in response to ethylene and shade. Based on these kinetics, we further investigated ethylene and shade-induced genome-wide gene expression changes in hypocotyls and cotyledons separately. Both treatments induced a more extensive transcriptome reconfiguration in the hypocotyls compared to the cotyledons. Bioinformatics analyses suggested contrasting regulation of growth promotion- and photosynthesis-related genes. These analyses also suggested an induction of auxin, brassinosteroid and gibberellin signatures and the involvement of several candidate regulators in the elongating hypocotyls. Pharmacological and mutant analyses confirmed the functional involvement of several of these candidate genes and physiological control points in regulating stress-escape responses to different environmental stimuli. We discuss how these signaling networks might be integrated and conclude that plants, when facing different stresses, utilise a conserved set of transcriptionally regulated genes to modulate and fine tune growth.