The long non-coding RNA MSTRG.32189-PcmiR399b-PcUBC24 module regulates the phosphate accumulation and disease resistance to Botryosphaeria dothidea in pear

Pear ring rot disease (Botryosphaeria dothidea) causes a significant threat to the healthy development of the pear industry. Recent research has identified the functional role of long noncoding RNAs (lncRNAs) in various biological processes of plants. The role of lncRNAs in pear defense response remains unknown. In this study, transcriptome sequencing was used to analyze long non-coding RNAs in pear stem infected with B. dothidea. It showed that 3,555 lncRNAs were identified, of which 286 lncRNAs were significantly differentially expressed. GO and KEGG analysis showed that cis- and trans-regulated target genes were enriched in multiple disease-resistant related pathways. More specifically, MSTRG.32189 predicted as an endogenous target mimic (eTM) was significantly down-regulated in response to B. dothidea infection, which was confirmed to inhibit the cleavage effect of PcmiR399b on PcUBC24. The transgenic Arabidopsis of OE-MSTRG.32189 exhibited lower Pi content and weaker disease resistance to Botrytis cinerea compared to WT. In pear callus, overexpression of MSTRG.32189 negatively regulated PcmiR399b, which decreased Pi content and reduced disease resistance. Whereas overexpressing PcmiR399b in pear callus exhibited the opposite effects compared with OE-MSTRG.32189. Overexpression and knock-out of PcUBC24 further clarified that PcUBC24 negatively regulate the Pi content and disease resistance to B. dothidea infection. Furthermore, the ROS levels and the expressions of disease resistance pathway-related genes were regulated by the MSTRG.32189-PcmiR399b-PcUBC24 module in transgenic pear callus, which contributed to disease resistance. Overall, our results demonstrated the role of lncRNAs in pear defense response, revealing MSTRG.32189-PcmiR399b-PcUBC24 module regulates phosphate accumulation and disease resistance to B. dothidea infection in pear.