CmGLK CmCHLH module regulates seed germination rate mediated by abscisic acid pathway in melon

The uniformity and speed of seedling emergence are particularly important in vegetable industrial seedling. A higher germination rate can decrease the seedling cycle and increase seedling uniformity in melon. However, the molecular mechanisms underlying the regulation of seed germination remain largely unknown in melon. Golden2-like (CmGLK) has been identified as a key transcription factor involved in chloroplast development in our previous study, and we also found that it plays a novel role in regulating seed germination rate in melon in this study. The near isogenic line of Cmglk (Cmglk-NIL) and CmGLK knockout mutants in melon exhibited slower seed germination rates than that in wild type lines, while the overexpression of CmGLK in tomato showed significantly increased germination rates. Comparative transcriptome analysis revealed that numerous ABA-related genes were involved in seed germination. Furthermore, the Cmglk-NIL and CmGLK knockout mutants exhibited increased sensitivity to exogenous ABA during seed germination, while the CmGLK overexpression lines in tomato showed reduced sensitivity to ABA. Bioinformatics analysis and experimental validation indicated that CmGLK could directly bind to the promoter of CmCHLH, thereby activating its expression. Overexpression of CmCHLH in tomato significantly increased seed germination rate, confirming its regulatory role. Taken together, these findings elucidate a CmGLK-CmCHLH regulatory module that regulates seed germination rate through ABA pathway in melon. This will not only enhance our understanding of the mechanisms underlying seed germination in melon, but also provide a reference for seed germination regulation for other crops.