OsTPP1 regulates seed germination through the crosstalk with abscisic acid in rice.

Seed germination is essential for direct seeding in rice. It has been demonstrated that trehalose-6-phosphate phosphatase 1 (OsTPP1) plays roles in improving yield and stress tolerance in rice. In this study, the roles of OsTPP1 on seed germination in rice were investigated. The tpp1 mutant germinated slower than the wild-type (WT), which can be restored by exogenous trehalose. tpp1 seeds showed higher ABA content compared with WT seeds. The tpp1 mutant was hypersensitive to ABA and ABA catabolism inhibitor (Dinicozanole). Furthermore, two ABA catabolism genes were downregulated in the tpp1 mutant which were responsible for increased ABA concentrations, and exogenous trehalose increased transcripts of ABA catabolism genes, suggesting that OsTPP1 and ABA catabolism genes acted in the same signaling pathway. Further analysis showed that a transcription factor of OsGAMYB was an activator of OsTPP1, and expression of OsGAMYB was decreased by both the exogenous and endogenous ABA, subsequently reducing the expression of OsTPP1, which suggested a new signaling pathway required for seed germination in rice. In addition, ABA-responsive genes, especially OsABI5, were invoved in OsTPP1-mediated seed germination. Overall, our study provided new pathways in seed germination that OsTPP1 controlled seed germination through crosstalk with the ABA catabolism pathway.