Abstract
Seed imbibition is a prerequisite for subsequent dormancy and germination control. Here, we investigated imbibition responses of Arabidopsis seeds by transcriptomic and hormone profile analyses using dormant (Cvi) and non-dormant (Col) accessions. Once imbibed, seeds of both accessions swelled most until 3h, reflecting water uptake. Microarray analysis showed that in both accessions, 15-min-, 30-min-, and 1-h-imbibed seeds were less active in gene expression than at 3h. More than 2000 genes were either up-regulated or down-regulated in 3-h-imbibed seeds. Some 3-h-up-regulated genes were already induced in 1-h-imbibed seeds, suggestive of genome reprogramming early after the onset of imbibition. Imbibition-induced genes in 3-h-imbibed seeds included those up-regulated in both Col and Cvi (common) or unique to either accession (accession-specific). Quantification of plant hormones showed that abscisic acid (ABA) and salicylic acid (SA) contents were higher, but gibberellinA4 (GA4), N6-(Δ2-isopentenyl) adenine (iP), jasmonic acid (JA), JA-Ile, and indole-3-acetic acid (IAA) were lower in imbibed seeds of Cvi compared to Col. In addition, changes in IAA and JA were initiated before 1h, whereas ABA and JA-Ile declined 3h after the onset of imbibition. An increase in GA4 and iP appeared to be correlated temporally with the initiation of secondary water uptake, which marks the completion of germination.
