time course-Transcriptome analysis of the hypocotyl growth switch

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 6 dye-swap - CATMA arrays