Regulation of the aurantio-obtusin accumulation by StTCP4.1-mediated StDA1-StHDR1 module in Senna tora seeds

Abstract

Senna tora (S. tora) is a commonly used Chinese medicinal plant due to the presence of the bioactive compounds anthraquinones in its mature seeds. Seed size is an important factor that affect S. tora yield quantity and quality. However, the mechanism regulating seed size and aurantio-obtusin biosynthesis in S.tora is still unclear. In this study, we identified the ubiquitin receptor StDA1 in S.tora that served as a negative regulator to seed formation and limited seed enlargement. Antisense overexpression of StDA1 led to larger seeds in S. tora and promoted the accumulation of aurantio-obtusin. In contrast, overexpression of StDA1 in S.tora resulted in a relative decrease in aurantio-obtusin accumulation. Moreover, StDA1 can directly bind to StHDR1and regulate its degradation through the 26S proteasome to regulate seed size and aurantio-obtusin accumulation. We also found that the StDA1-StHDR1 module is responsive to the MeJA via StTCP4.1, which in turn affects the accumulation of aurantio-obtusin. Overall, we have identified a protein complex that regulates the accumulation of aurantio-obtusin, StTCP4.1-StDA1-StHDR1, as a potential target for improving S.tora yield quantity and quality.