Differential expression of brassinosteroid signaling pathway genes in root-knot nematode-resistant and susceptible sweetpotato cultivars during Meloidogyne incognita infection

초록

Root-knot nematodes (RKNs), especially Meloidogyne incognita, represent a major constraint on sweetpotato (Ipomoea batatas [L.] Lam) production globally. However, the role of brassinosteroid (BR) signaling in mediating RKN resistance remains unclear. Transcriptome analyses of RKN-resistant cultivars (RCs: Danjami, Pungwonmi, and Juhwangmi) and susceptible cultivars (SCs: Dahomi, Shinhwangmi, and Yulmi) revealed differential regulation of BR signaling genes during both constitutive and infection-induced defense responses. In this study, BR pathway genes related to BAK1-, BZR1-, and BRU1-like components were extracted from RNA-seq datasets and analyzed to characterize their expression patterns following M. incognita infection. Heatmap analysis revealed early and strong induction of BR genes in SCs, but downregulation or only weak activation in RCs. qRT-PCR analysis of the representative cultivars Yulmi (SC) and Juhwangmi (RC) confirmed strong and sustained expression of BR genes in Yulmi, in contrast to the delayed or reduced responses observed in Juhwangmi. These findings suggest that early activation of BR signaling may promote susceptibility by prioritizing growth over defense, while its suppression in RCs facilitates defense responses. This study provides the first transcriptomic evidence that BR signaling differentially contributes to RKN resistance in sweetpotato and identifies BR pathway components as potential targets for the development of resistant cultivars.

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