Transcription Factors HmeWRKY33 and HmeWRKY51 Regulate the Susceptibility of Pitaya to Canker Disease

Pitaya canker disease, caused by Neoscytalidium dimidiatum, is the primary threat to pitaya cultivation, significantly compromising fruit quality and reducing yield. WRKY transcription factors are essential regulators in plant pathogen recognition and defense mechanisms, yet their specific roles in the development of pitaya canker disease remain largely unexplored. In this study, five genes (HmeWRKY33, HmeWRKY51, HmePR1, HmeHsp70, and HmeSERK) associated with pitaya canker disease were identified through RNA-Seq analysis. The expression levels of HmeWRKY33 and HmeWRKY51 were upregulated following N. dimidiatum infection. Transient transformation revealed that these five genes negatively influenced the resistance of Nicotiana benthamiana leaves to canker disease while promoting the accumulation of reactive oxygen species and inducing cell death. Yeast one-hybrid and dual luciferase reporter assays revealed that HmeWRKY33 directly activated the expression of HmeSERK, while HmeWRKY51 directly inhibited the expression of HmePR1 and HmeHsp70, coparticipating in regulating the susceptibility of ‘Youcihuanglong’ pitaya to canker. These findings provide a theoretical basis for breeding new canker-resistant pitaya varieties through genetic transformation.