Functional Characterization of the Gibberellin (GA) Receptor ScGID1 in Sugarcane.

Sugarcane smut caused by Sporisorium scitamineum represents the most destructive disease in the sugarcane industry, causing host hormone disruption and producing a black whip-like sorus in the apex of the stalk. In this study, the gibberellin metabolic pathway was found to respond to S. scitamineum infection, and the contents of bioactive gibberellins were significantly reduced in the leaves of diseased plants. The gibberellin receptor gene ScGID1 was identified and significantly downregulated. ScGID1 localized in both the nucleus and cytoplasm and had the highest expression level in the leaves. Eight proteins that interact with ScGID1 were screened out using a yeast two-hybrid assay. Novel DELLA proteins named ScGAI1a and ScGA20ox2, key enzymes in GA biosynthesis, were both found to interact with ScGID1 in a gibberellin-independent manner. Transcription factor trapping with a yeast one-hybrid system identified 50 proteins that interacted with the promoter of ScGID1, among which ScS1FA and ScPLATZ inhibited ScGID1 transcription, while ScGDSL promoted transcription. Overexpression of ScGID1 in transgenic Nicotiana benthamiana plants could increase plant height and promote flowering. These results not only contribute to improving our understanding of the metabolic regulatory network of sugarcane gibberellin but also expand our knowledge of the interaction between sugarcane and pathogens.