JA differentially regulates a SmWLIM1/MYB62-SUS1 module to control male fertility via starch biosynthesis

Abstract Male sterility is a valuable trait for hybrid breeding, and starch metabolism plays a crucial role in regulating fertility. However, the molecular mechanisms underlying pollen fertility in the medicinal plant Salvia miltiorrhiza remain unclear. In this study, comparative transcriptome and starch content analyses of anthers from a naturally sterile Sichuan (SC) genotype and a fertile Shandong (SD) genotype identified the sucrose synthase gene SmSUS1 as a key regulator. This work provides the first functional evidence that SmSUS1 positively regulates pollen fertility by promoting starch biosynthesis. Using Weighted gene co-expression network analysis, two upstream transcription factors (TFs), SmWLIM1 and SmMYB62, were further uncovered. In vitro and in vivo assays demonstrated that both transcription factors directly activate SmSUS1 expression, forming a transcriptional module essential for fertility regulation. Jasmonic acid (JA) signaling differentially regulates this module, primarily by suppressing SmWLIM1 expression, which subsequently downregulates SmSUS1 and leads to reduced pollen viability. Although SmMYB62 expression responds to JA, its dynamics do not directly correlate with fertility. Notably, this entire JA-SmWLIM1-SmSUS1 regulatory axis operates specifically in the fertile SD genotype, revealing a genotype-dependent hormonal control of male fertility. Our study elucidates not only a core transcriptional module governing fertility but also a novel genotype-specific JA-starch metabolism pathway, providing crucial regulatory targets and genetic resources for hybrid breeding in medicinal plants.