Cyclic nucleotide gated channel gene family in tomato: genome-wide identification and functional analyses in disease resistance

The cyclic nucleotide gated channel (CNGC) is suggested to be one of the important calcium conducting channels. Nevertheless, genome-wide identification and systemic functional analysis of CNGC gene family in crop plant species have not yet been conducted. In this study, we performed genome-wide identification of CNGC gene family in the economically important crop tomato (Solanum lycopersicum L.) and analyzed function of the group IVb SICNGC genes in disease resistance. Eighteen CNGC genes were identified in tomato genome, and four CNGC loci that were misannotated at database were corrected by cloning and sequencing. Detailed bioinformatics analyses on gene structure, domain composition and phylogenetic relationship of the SICNGC gene family were conducted and the group-specific feature was revealed. Comprehensive expression analyses demonstrated that SICNGC genes were highly, widely but differently responsive to diverse stimuli. Pharmacological assays showed that the putative CNGC activators cGMP and cAMP enhanced resistance against Sclerotinia sclerotiorum. Silencing of group IVb SICNGC genes significantly enhanced resistance to fungal pathogens Pythium aphaniderma turn and S. sclerotiorum, strongly reduced resistance to viral pathogen Tobacco rattle virus, while attenuated PAMP- and DAMPtriggered immunity as shown by obvious decrease of the flg22- and AtPepl -elicited hydrogen peroxide accumulation in S/CNGC-silenced plants. Additionally, silencing of these SICNGC genes significantly altered expression of a set of Ca2+ signaling genes including SICaMs, SICDPKs, and SICAMTA3. Collectively, our results reveal that group IV SICNGC genes regulate a wide range of resistance in tomato probably by affecting Ca2+ signaling.