Abstract
Seed dormancy and germination are controlled by multiple environmental and endogenous factors. We have previously shown that both red light and cold treatment upregulate the gibberellin (GA) biosynthesis gene AtGA3ox1. Besides the synthesis of bioactive GAs, their deactivation by GA 2-oxidases is another possible mechanism for controlling the level of this hormone. Our QRT-PCR analysis indicated that AtGA2ox2, which encodes a GA 2-oxidase, was highly upregulated when seeds were imbibed in the dark at 22°C following a far-red (FR) light pulse that inhibits germination. In a loss-of-function AtGA2ox2 mutant, the inhibitory effect of FR light and dark incubation on germination was reduced, suggesting a role of AtGA2ox2 in maintaining a low level of bioactive GAs. These results suggest that GA deactivation plays a role in modulating the level of bioactive GAs in response to environmental signals during Arabidopsis seed germination.
