Transcriptome Profile in a Susceptible Pear ‘Zaosu’ ( Pyrus bretschneideri Rehd.)– Valsa pyri Interaction

Pear production was seriously threatened by Valsa canker, a notorious disease caused by the necrotrophic fungus Valsa pyri ( Vp ), but the molecular mechanism is elusive. Currently, the dynamic gene expression profiles of main susceptible variety ‘Zaosu’ ( Pyrus bretschneideri Rehd.) in response to Vp were investigated using RNA sequencing (RNA-seq). In total, 286, 1912, and 6321 differentially expressed genes (DEGs) were detected from the infected phloem tissues at 1, 2, and 4 days after infection, respectively. Functional terms “Stress biotic”, “Signaling. receptor kinase”, and “Plant hormone signal transduction” were significantly enriched. DEGs associated with Ethylene, Chitinase, Glycosyl hydrolase, and receptor-like kinase (RLK) subfamilies LysM and WAK_LRK10L-1 were mainly up-regulated and contributed to induction of the immune responses in ‘Zaosu’. On the contrary, DEGs involved in auxin and brassinosteroid signals, receptor-like protein, nucleotide-binding leucine-rich repeat (NB-LRR), and RLK subfamilies CrRLK1L-1, LRR-III, LRR-VII, and LRR-XII are mainly down-regulated, which are the reasons why ‘Zaosu’ fails to prevent Vp invasion. Our results highlight new insights into pear responses against Vp and perhaps other necrotrophs.