Abstract
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 SlCNGC 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 SlCNGC gene family were conducted and the group-specific feature was revealed. Comprehensive expression analyses demonstrated that SlCNGC 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 SlCNGC genes significantly enhanced resistance to fungal pathogens Pythium aphanidermatum and S. sclerotiorum, strongly reduced resistance to viral pathogen Tobacco rattle virus, while attenuated PAMP- and DAMP-triggered immunity as shown by obvious decrease of the flg22- and AtPep1-elicited hydrogen peroxide accumulation in SlCNGC-silenced plants. Additionally, silencing of these SlCNGC genes significantly altered expression of a set of Ca2+ signaling genes including SlCaMs, SlCDPKs, and SlCAMTA3. Collectively, our results reveal that group IV SlCNGC genes regulate a wide range of resistance in tomato probably by affecting Ca2+ signaling.
Highlights
The cyclic nucleotide gated channels (CNGCs) are ligand-gated cation channels localized typically in plasma membrane (Chin et al, 2009; Ma et al, 2009)
These results suggest that Ca2+ channels, which are regulated by cNMPs such as CNGCs, may play a role in tomato resistance to S. sclerotiorum
We identified CNGC gene family in the economically important crop tomato (Solanum lycopersicum L.) and analyzed function of the group IV SlCNGC genes in disease resistance, representing the first genome-wide identification and functional analysis of CNGC gene family in dicotyldons crop species
Summary
The cyclic nucleotide gated channels (CNGCs) are ligand-gated cation channels localized typically in plasma membrane (Chin et al, 2009; Ma et al, 2009). A plant CNGC-specific motif spanning the phosphate binding cassette (PBC) and hinge region within CNB domain of CNGC proteins is predicted This motif identifies CNGCs but no other protein and represents an efficient tool to identify plant CNGCs, which has been validated in several species such as Arabidopsis, rice, P. patens and Selaginella moellendorffii (Zelman et al, 2012, 2013). It has been suggested that plant CNGCs might conduct calcium They might be activated by direct binding of cyclic nucleotides such as cAMP and cGMP to the CNB domain and inhibited by binding of CaM to the CaMB domain (Chin et al, 2009; Wang et al, 2013). AtCNGC18 is activated by a calciumdependent protein kinase AtCPK32 in Xenopus laevis oocytes (Zhou et al, 2014)
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