Find in Library

Seed germination is a complex process that is regulated by various exogenous and endogenous factors, in which abscisic acid (ABA) plays a crucial role. The triphosphate tunnel metalloenzyme (TTM) superfamily exists in all living organisms, but research on its biological role is limited. Here, we reveal that <i>TTM2</i> functions in ABA-mediated seed germination. Our study indicates that <i>TTM2</i> expression is enhanced but repressed by ABA during seed germination. Promoted <i>TTM2</i> expression in <i>35S::TTM2-FLAG</i> rescues ABA-mediated inhibition of seed germination and early seedling development and <i>ttm2</i> mutants exhibit lower seed germination rate and reduced cotyledon greening compared with the wild type, revealing that the repression of <i>TTM2</i> expression is required for ABA-mediated inhibition of seed germination and early seedling development. Further, ABA inhibits <i>TTM2</i> expression by ABA insensitive 4 (ABI4) binding of <i>TTM2</i> promoter and the ABA-insensitive phenotype of <i>abi4-1</i> with higher <i>TTM2</i> expression can be rescued by mutation of <i>TTM2</i> in <i>abi4-1 ttm2-1</i> mutant, indicating that <i>TTM2</i> acts downstream of <i>ABI4</i>. In addition, <i>TTM1</i>, a homolog of <i>TTM2</i>, is not involved in ABA-mediated regulation of seed germination. In summary, our findings reveal that TTM2 acts as a downstream factor of ABI4 in ABA-mediated seed germination and early seedling growth.