Dry seeds accumulate translatable mRNAs as well as functional proteins for transcription and translation. They are possibly involved in early physiological responses after imbibition, however, their functions remain poorly understood. The aim of this study is to investigate the function of seed stored transcriptional machinery in resumption of gene expression after the onset of imbibition in Arabidopsis thaliana. First, we examined the characters of stored mRNAs in A. thaliana dry seeds using microarray data from non-dormant Columbia (Col) and dormant Cape Verde Islands (Cvi) accessions. Transcriptomes of Col and Cvi dry seeds resembled one another, suggesting that patterns of stored mRNA do not reflect either the degree of dormancy or germination potential, but rather reflect the developmental context, such as seed maturation. Upon imbibition, changes in mRNA abundance of many genes were initiated between 1- and 2-h after the onset of imbibition. RT-PCR expression analysis of imbibition-responsive genes indicates that early induction was not altered by treatment of cycloheximide. This suggests that de novo protein synthesis is not required for gene expression during early imbibition stages. Moreover, controlled deterioration treatment (CDT), which causes artificial damages on dry seeds, disrupted gene expression specifically during the first 3 h after the start of imbibition, suggesting that seed stored transcription factors play a pivotal role in gene expression during early imbibition periods. Furthermore, the negligible effect of CDT on germination indicates that early imbibition response is dispensable and de novo synthesized proteins compensate for the function of stored proteins for germination.
