Abstract
Temperature is a main environmental cue that directs the season of germination of winter- and summer-annual seeds. The seeds of winter-annuals, such as Arabidopsis, are dispersed in spring but their germination is suppressed by high temperature during summer. Supraoptimal and suboptimal temperatures often inhibit germination of crop seeds and reduce efficiency of their production severely. We used Arabidopsis as a model, and found that high temperature enhances expression of NCED9, and suppresses germination through the action of ABA in continuous light condition. In red-light pulse condition, however, ABA may not be a main factor since germination of ABA deficient mutant seeds was inhibited by high temperature. PIL5 is shown to be a main germination suppressor in far-red light pulse condition. Analyses of PIL5 loss of function mutant seeds indicated that high temperature suppresses germination through the action of PIL5 in this condition. We also found PIF4, which is shown to work on high temperature response of the seedlings, is another germination suppressor. We will discuss how temperature regulate the action of these germination suppressors.
