A rice F-box gene, OsFbx352, is involved in glucose-delayed seed germination in rice

F-box proteins play diverse roles in regulating numerous physiological processes in plants. This study isolated a gene (OsFbx352) from rice encoding an F-box domain protein and characterized its role in seed germination. Expression of OsFbx352 was upregulated by abscisic acid (ABA). The transcripts of OsFbx352 were increased upon imbibition of rice seeds and the increase was markedly suppressed by glucose. Germination of seeds with overexpression of OsFbx352 was less suppressed by glucose than that of wild-type seeds, while glucose had greater inhibition for germination of seeds with knockdown of OsFbx352 by RNA interference (RNAi) than that of wild-type seeds. The differential response of germination of the transgenic and wild-type seeds to glucose may be accounted for by differences in ABA content among overexpressing, RNAi, and wild-type seeds such that overexpression of OsFbx352 and knockdown of OsFbx352 led to lower and higher ABA contents, respectively, than that of wild-type seeds in the presence of glucose. Overexpression of OsFbx352 led to a reduction in expression of genes responsible for ABA synthesis (OsNced2, OsNced3) and an increase in expression of genes encoding ABA catabolism (OsAba-ox2, OsAba-ox3) in the presence of glucose. These findings indicate that OsFbx352 plays a regulatory role in the regulation of glucose-induced suppression of seed germination by targeting ABA metabolism.