Triphosphate Tunnel Metalloenzyme 2 Acts as a Downstream Factor of ABI4 in ABA-Mediated Seed Germination.

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 functions in ABA-mediated seed germination. Our study indicates that expression is enhanced but repressed by ABA during seed germination. Promoted expression in rescues ABA-mediated inhibition of seed germination and early seedling development and mutants exhibit lower seed germination rate and reduced cotyledon greening compared with the wild type, revealing that the repression of expression is required for ABA-mediated inhibition of seed germination and early seedling development. Further, ABA inhibits expression by ABA insensitive 4 (ABI4) binding of promoter and the ABA-insensitive phenotype of with higher expression can be rescued by mutation of in mutant, indicating that acts downstream of . In addition, , a homolog of , 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.