Abstract
BackgroundCysteine-rich receptor-like kinases (CRKs) represent a large subfamily of receptor-like kinases and play vital roles in diverse physiological processes in regulating plant growth and development.ResultsCaCRK5 transcripts were induced in pepper upon the infection of Ralstonia solanacearum and treatment with salicylic acid. The fusions between CaCRK5 and green fluorescence protein were targeted to the plasma membrane. Suppression of CaCRK5 via virus-induced gene silencing (VIGS) made pepper plants significantly susceptible to R. solanacearum infection, which was accompanied with decreased expression of defense related genes CaPR1, CaSAR8.2, CaDEF1 and CaACO1. Overexpression of CaCRK5 increased resistance against R. solanacearum in Nicotiana benthamiana. Furthermore, electrophoretic mobility shift assay and chromatin immunoprecipitation coupled with quantitative real-time PCR analysis revealed that a homeodomain zipper I protein CaHDZ27 can active the expression of CaCRK5 through directly binding to its promoter. Yeast two-hybrid and bimolecular fluorescence complementation (BiFC) analyses suggested that CaCRK5 heterodimerized with the homologous member CaCRK6 on the plasma membrane.ConclusionsOur data revealed that CaCRK5 played a positive role in regulating immune responses against R. solanacearum infection in pepper.
Highlights
Cysteine-rich receptor-like kinases (CRKs) represent a large subfamily of receptor-like kinases and play vital roles in diverse physiological processes in regulating plant growth and development
SMART analysis of the domain architecture predicted that CaCKR5 was composed of two cysteine-rich Domain of Unknown Function 26 (DUF26) domains (PFAM01657, Stressantifung domain), a transmembrane region and a serine/ threonine kinase domain (PFAM07714), and CaCRK5 belongs to the family of cysteine-rich kinases [10]
In summary, our data suggest that CaCRK5 significantly contributes to immune defense against R. solanacearum in pepper and N. benthamiana
Summary
Cysteine-rich receptor-like kinases (CRKs) represent a large subfamily of receptor-like kinases and play vital roles in diverse physiological processes in regulating plant growth and development. When plants are attacked by pathogens, plant immune receptors can detect pathogen infection and elicit a battery of defense responses. As the first line of plant defense, pattern recognition receptors (PRRs) recognize microbe-associated molecular patterns (MAMPs) that are released by the pathogen during infection and trigger plant immunity [1]. Well-characterized PRRs include the Arabidopsis leucine-rich repeat (LRR) receptor kinases FLAGELLIN SENSING 2 (FLS2) and EF-TU RECEPTOR (EFR), which can recognize bacterial flagellin [4] and EFTu [5], respectively. Roles for most RLKs are unknown, many RLKs were reported to regulate plant physiological processes, including development, hormone perception and defense responses [8]
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