StMYC1, a JA signaling transcription factor, enhances tuber yield and confers herbivore resistance in potato

The basic helix-loop-helix (bHLH) transcription factors MYC2 and its paralogs are master regulators in jasmonate (JA) signaling in Arabidopsis, yet their functions in potato (Solanum tuberosum) remain poorly understood. Here, we identified and characterized StMYC1, a potato transcription factor that clusters phylogenetically with tomato SlMYC1 and contains conserved JASMONATE ZIM-DOMAIN (JAZ)-interacting and bHLH domains. Overexpression of StMYC1 in Arabidopsis recapitulated canonical JA-hyperresponsive phenotypes in plant development and defense responses, confirming its functional conservation in the JA signaling pathway. Yeast two-hybrid assays demonstrated that StMYC1 interacts with Arabidopsis JAZ repressors and potato StJAZ1-like, indicating its integration into the core JA signaling module. Transcriptome analysis revealed that StMYC1 reprograms the gene expression profile in Arabidopsis leaves to enhance defense-related gene expression while repressing genes associated with plant growth. Strikingly, overexpression of StMYC1 in potato conferred a dual beneficial effect, including increased microtuber yield under in vitro conditions and enhanced resistance to Spodoptera exigua. Physiological and molecular analyses showed that StMYC1 improves photosynthetic capacity in source leaves and upregulates the expression of genes involved in sucrose transport, starch biosynthesis, and tuberization in sink microtubers. Moreover, StMYC1 enhances the constitutive and inducible accumulation of steroidal glycoalkaloids (SGAs), as well as the inducible expression of JA-responsive defense genes, in potato leaves. Our work demonstrates that StMYC1 is a conserved JA signaling component that coordinately improves herbivore resistance and microtuber production in potato likely by enhancing source capacity and redirecting resource allocation to favor both tuber storage and leaf defense. These results highlight StMYC1 as a promising target for breeding potato varieties with enhanced herbivore resistance and tuber yield, and provide insights for the genetic improvement of other storage-organ crops.