LncRNA33732-respiratory burst oxidase module associated with WRKY1 in tomato- Phytophthora infestans interactions.

Our previous studies indicated that tomato WRKY1 transcription factor acts as a positive regulator during tomato resistance to Phytophthora infestans. However, the molecular mechanism of WRKY1-mediated resistance regulation remains unclear. Here, we used a comparative transcriptome analysis between wild-type and WRKY1-overexpressing tomato plants to identify differentially expressed genes (DEGs) and long non-coding RNAs (DELs), and we examined long non-coding RNA (lncRNA)-gene networks. The promoter sequences of the upregulated DEGs and DELs were analyzed. Among 1073 DEGs and 199 DELs, 1 kb 5'-upstream regions of 59 DEGs and 22 DELs contain the W-box, the target sequence of the WRKY1. The results of promoter-β-glucuronidase (GUS) fusion and yeast one-hybrid assay showed that lncRNA33732 was activated by WRKY1 through sequence-specific interactions with the W-box element in its promoter. The overexpression and silencing analysis of lncRNA33732 in tomato showed that lncRNA33732 acts as a positive regulator and enhanced tomato resistance to P. infestans by induction of the expression of respiratory burst oxidase (RBOH) and increase in the accumulation of H2 O2 . When the expression of RBOH gene was inhibited in tomato plants, H2 O2 accumulation decreased and resistance were impaired. These findings suggest that lncRNA33732 activated by WRKY1 induces RBOH expression to increase H2 O2 accumulation in early defense reaction of tomato to P. infestans attack. Our results provide insights into the WRKY1-lncRNA33732-RBOH module involved in the regulation of H2 O2 accumulation and resistance to P. infestans, as well as provide candidates to enhance broad-spectrum resistance to pathogens in tomato.