Project description:ra03-04_elongation_isoxaben - isoxaben treatment - 1. Study the molecular basis of the growth acceleration observed in hypocotyl cells. We previously have observed that cell elongation takes place in two distinct phases (Refregier et al., 2004). A slow growth phase during which a thick polylamellated wall is deposited and a rapid growth phase during which cell wall polymers are extensively remodelled. In dark-grown hypocotyls the slow growth phase takes place during the first 48h after seed-imbibition synchronously in all cells. At 48h after imbibition, cells at the basis of the hypocotyl undergo a growth acceleration, this acceleration follows an acropetal gradient along the hypocotyl. In this experiment, we investigated the changes in transcript abundance that accompany this sudden increase in growth rate. 2. Study the feed-back mechanisms involved in the coordination between cellulose synthesis and the cell elongation. The inhibition of cellulose using chemical inhibitors also inhibits cell elongation. In the same study (Refregier et al., 2004), we have observed that the effect of the cellulose synthesis inhibitor isoxaben on cell elongation is different dependent on the growth stage. When applied during the slow growth phase, cells continue to elongate slowly and do not show the growth acceleration at 48h after imbibition. Surprisingly, when applied after the growth acceleration, isoxaben does not inhibit subsequent growth. In this study we compared the effects of isoxaben on the transcript profiles before and after the growth acceleration. This should inform us about the response of the hypocotyl cells to the inhibition of cellulose and should provide insights into the molecular events that underly the observed coupling between cellulose synthesis and cell elongation. - 1- 45 hours, transfer to medium +/-isoxaben, harvest at 48 hours: comparison 48 hours + /- isoxaben. 2- 52 hours, transfer on + /-isoxaben, harvest 55 hours: comparison 55 hours + /-isoxaben (after transition: inhibition synthesis of cellulose, no inhibition of cellular elongation). Keywords: treated vs untreated comparison
Project description:1. Study the molecular basis of the growth acceleration observed in hypocotyl cells. We previously have observed that cell elongation takes place in two distinct phases (Refregier et al., 2004). A slow growth phase during which a thick polylamellated wall is deposited and a rapid growth phase during which cell wall polymers are extensively remodelled. In dark-grown hypocotyls the slow growth phase takes place during the first 48h after seed-imbibition synchronously in all cells. At 48h after imbibition, cells at the basis of the hypocotyl undergo a growth acceleration, this acceleration follows an acropetal gradient along the hypocotyl. In this experiment, we investigated the changes in transcript abundance that accompany this sudden increase in growth rate. 2. Study the feed-back mechanisms involved in the coordination between cellulose synthesis and the cell elongation. The inhibition of cellulose using chemical inhibitors also inhibits cell elongation. In the same study (Refregier et al., 2004), we have observed that the effect of the cellulose synthesis inhibitor isoxaben on cell elongation is different dependent on the growth stage. When applied during the slow growth phase, cells continue to elongate slowly and do not show the growth acceleration at 48h after imbibition. Surprisingly, when applied after the growth acceleration, isoxaben does not inhibit subsequent growth. In this study we compared the effects of isoxaben on the transcript profiles before and after the growth acceleration. This should inform us about the response of the hypocotyl cells to the inhibition of cellulose and should provide insights into the molecular events that underly the observed coupling between cellulose synthesis and cell elongation.
Project description:Transcriptional profiling of hypocotyl comparing wild type with shr mutant. We used Affymetrix ATH1 microarrays to determine the effect of GRAS transcription factor SHORT-ROOT on growth and development of Arabidopsis shoot system (hypocotyl) by global transcriptome analysis and to identify the key players in the regulatory pathway.
Project description:ra03-04_elongation_isoxaben - time course - 1. Study the molecular basis of the growth acceleration observed in hypocotyl cells. We previously have observed that cell elongation takes place in two distinct phases (Refregier et al., 2004). A slow growth phase during which a thick polylamellated wall is deposited and a rapid growth phase during which cell wall polymers are extensively remodelled. In dark-grown hypocotyls the slow growth phase takes place during the first 48h after seed-imbibition synchronously in all cells. At 48h after imbibition, cells at the basis of the hypocotyl undergo a growth acceleration, this acceleration follows an acropetal gradient along the hypocotyl. In this experiment, we investigated the changes in transcript abundance that accompany this sudden increase in growth rate. 2. Study the feed-back mechanisms involved in the coordination between cellulose synthesis and the cell elongation. The inhibition of cellulose using chemical inhibitors also inhibits cell elongation. In the same study (Refregier et al., 2004), we have observed that the effect of the cellulose synthesis inhibitor isoxaben on cell elongation is different dependent on the growth stage. When applied during the slow growth phase, cells continue to elongate slowly and do not show the growth acceleration at 48h after imbibition. Surprisingly, when applied after the growth acceleration, isoxaben does not inhibit subsequent growth. In this study we compared the effects of isoxaben on the transcript profiles before and after the growth acceleration. This should inform us about the response of the hypocotyl cells to the inhibition of cellulose and should provide insights into the molecular events that underly the observed coupling between cellulose synthesis and cell elongation. - 1- Time course from 45h until 55h after seed-imbibition, comparisons respectively between: 45h - 48h, 48h - 52h, 52h - 55h Keywords: time course
Project description:Plant cells are surrounded by walls, which must often meet opposing functional requirements during plant growth and defense. The cells meet them by modifying wall structure and composition in a tightly controlled and adaptive manner. The modifications seem to be mediated by a dedicated cell wall integrity (CWI) maintenance mechanism. Currently the mode of action of the mechanism is not understood and it is unclear how its activity is coordinated with established plant defense signaling. We investigated both the responses to cell wall damage (CWD) compromising CWI and the underlying mechanism in Arabidopsis thaliana. A cellulose biosynthesis inhibitor isoxaben was used as a tool to induce the loss of cell wall integrity. Isoxaben was chosen because it only affects a certain cell type / differentiation stage, and weakens the cell walls indirectly by inhibiting a biosynthetic process, making CWD occurrence dependent on high turgor levels (allowing simultaneous manipulation of the responses by addition of osmotica like sorbitol, mannitol, etc.). Isoxaben treatment causes structural damage, induction of lesion formation, cell death, deposition of lignin and callose as well as production of jasmonic acid and salicylic acid. Isoxaben-resistant mutant ixr1-1 is included to ensure the specificity of the treatment.
Project description:The cell wall is a crucial structure in plant cells, and modifications in its composition often have a major impact on growth and development. However, the molecular mechanisms responsible for the negative effects of cell wall alterations on plant growth are largely unknown. It was previously shown that a reduction in the levels of de-esterified homogalacturonan, a major pectin component of cell walls, in Arabidopsis thaliana plants expressing a fungal polygalacturonase or mutated in the QUASIMODO2 gene (qua2-1 plants), cause severe growth defects. Here we show that the class III peroxidase AtPrx71 is strongly up-regulated in these plants, as well as in response to alterations of other wall structural components, including treatments the cellulose synthase inhibitor isoxaben. Analysis of atprx71 loss-of-function mutants and of plants overexpressing AtPrx71 indicates that this gene negatively affects Arabidopsis growth at different stages of development. Furthermore, lack of AtPrx71 partially suppresses the dwarf phenotype of qua2-1, suggesting that this protein contributes to the growth defects observed in plants undergoing cell wall damage. AtPrx71 appears to promote the production of reactive oxygen species in qua2-1 plants, as well as in plants treated with isoxaben. We propose that production of reactive oxygen species mediated by AtPrx71 negatively regulates Arabidopsis growth both during physiological development and in response to loss of cell wall integrity.
Project description:We found that Arabidopsis plants constitutively expressing OsRR6 exhibit reduced cytokinin sensitivity, adventitious root formation and enhanced anthocyanin accumulation. In addition they are hypersensitive to red, far-red and blue light in hypocotyl growth assay and also flower little early as compared to wild type.Therefore, to identify the downstream pathways affected in the OsRR6 overexpression plants, we performed transcriptome profiling of overexpression line vs wild type using Affymetrix microarray platform.