Studies On Early Events In Response To Seed Imbibition In Arabidopsis

Abstract

We carried out gene expression analysis on early stages of seed imbibition. Non-dormant Arabidopsis seeds imbibed at 15-, 30-, 60- and 180-min were analyzed using Affymetrix ATH1 Arrays. No up-regulated genes were found until 30 min, and Zat12 (At5g59820) was the only gene significantly up-regulated at 1 hour. After 3 hours, expression of about 2,200 genes was induced. These included AtNCED9, CYP707A2 and ABI4, and several genes associating with biogenesis of reactive oxygen species. Moreover, we found about 1,900 down-regulated genes at 3 hours. ABRE (CACGTG) was overrepresented in their promoters. LC-MS/MS analysis revealed that endogenous ABA level was drastically decreased after 3 hours. QRT-PCR analysis showed that CYP707A2 expression was induced 3 hours after imbibition. Interestingly, expression levels of ABI3, ABI4, and ABI5 were changed after 3 hours. These results suggested that the reduction in the ABA levels affects gene expression at 3 hours of imbibition.