Systematic identification of lysin-motif receptor-like kinases (LYKs) in Citrus sinensis, and analysis of their inducible involvements in citrus bacterial canker and phytohormone signaling

Abstract

Lysin motif receptor-like kinases (LYKs) plays a crucial role in plant-microbe interaction. During microbial infection, LYK recognizes the microbial entry into the host cell and triggers plant defense responses against pathogens. The citrus LYK family and its roles in the citrus bacterial canker (CBC) caused by Xanthomonas citri subsp. citri (Xcc) remains uncertain. In this study, we have performed a systematic annotation of CsLYK family and analyzed the altered expression patterns of genes induced by Xcc and biotic stress-related phytohormones (abscisic acid, methyl-jasmonate, and salicylic acid). We found that the Citrus sinensis genome harbors 9 LYK genes, which were further divided into 3 subgroups, and localized on 5 chromosomes and the unassembled scaffolds. They were characterized by the classic lysM and a Pkinase domain, and were found to be primarily localized on the plasma membrane. Most of the CsLYK family members were involved in a putative protein-protein interaction network. Expression profiles showed that CsLYKs could be induced by Xcc infection and some phytohormones. This highlights the correlation between the LYKs and the CBC resistance. These findings extend our understanding of LYKs in citrus, notably their roles in CBC studies. Besides, this study highlights the potential role of plant LYKs involved in pathogen resistance.