Transcription factor OsMYB30 increases trehalose content to inhibit α-amylase and seed germination at low temperature.

Low temperature germination (LTG) is an important agronomic trait for direct-seeding cultivation of rice (Oryza sativa). Both OsMYB30 and OsTPP1 regulate the cold stress response in rice, but the function of OsMYB30 and OsTPP1 in regulating LTG and the underlying molecular mechanism remain unknown. Employing transcriptomics and functional studies revealed a sugar signaling pathway that regulates seed germination in response to low temperature. Expression of OsMYB30 and OsTPP1 was induced by low temperature during seed germination, and overexpressing either OsMYB30 or OsTPP1 delayed seed germination and increased sensitivity to low temperature during seed germination. Transcriptomics and qPCR revealed that expression of OsTPP1 was upregulated in OsMYB30-overexpressing lines but downregulated in OsMYB30-knockout lines. In vitro and in vivo experiments revealed that OsMYB30 bound to the promoter of OsTPP1 and regulated the abundance of OsTPP1 transcripts. Over accumulation of trehalose was found in both OsMYB30- and OsTPP1-overexpressing lines, resulting in inhibition of α-amylase 1a (OsAMY1a) gene during seed germination. Both low temperature and exogenous trehalose treatments suppressed the expression of OsAMY1a, and the osamy1a mutant was not sensitive to exogenous trehalose during seed germination. Overall, we concluded that OsMYB30 expression was induced by low temperature to activate the expression of OsTPP1 and increase trehalose content, which thus inhibited α-Amylase activity and seed germination. This study identified a phytohormone-independent pathway that integrates environmental cues with internal factors to control seed germination.