| Sweet cherry is one of the main horticultural cash crops in our country,containing abundant nutritional components and important economic value.Sweet cherry is subjected to various biotic and abiotic stresses during its growth,such as drought,salinization,and pathogen threats.Therefore,it is of great theoretical and practical significance to screen the genes of anti-stress sweet cherry by molecular biological means.Receptor-like kinases（RLKs）are a class of transmembrane proteins located on the cell membrane.RLKs serve as bridges between the perception of external stimuli and the transmission of input signals,which can perceive external signals,convert extracellular signals into intracellular signals,and ultimately lead to the expression of appropriate target genes,thereby affecting the changes of biological individuals.The structural domains of plant RLKsconsist of an N-terminal signal sequence,an extracellular domain,a transmembrane domain,and a cytoplasmic domain with kinase activity.The characteristics of RLK family members lie in the diversity of the extracellular domain,which are divided into various subfamilies,and the diversity of the extracellular domain promotes the widespread signal perception of cells.Cysteine-rich receptor-like kinases（CRKs）,which are a subfamily of RLKscontaining a high content of cysteine,have been reported in recent years to play important roles in plant growth and development,immune responses,and abiotic stress as receptors for various signals.However,their function in stress resistance of sweet cherry has not been reported.This study used bioinformatics and molecular biology methods to explore the role of Pa CRKs in response to salt stress in plants.Using bioinformatics methods,40Pa CRKs were identified from the data in the sweet cherry database.Chromosomal localization and phylogenetic analysis of Pa CRKs indicated that Pa CRKs clustered on the same chromosome were also preferentially clustered in the same subgroup,suggesting that the Pa CRKs genes may have originated from gene duplication.Expression patterns analysis of Pa CRKs in the root system under four stress conditions revealed that the expression levels of Pa CRKs were different under salt,Pseudomonas syringae,droght,and abscisic acid treatments.Among them,salt stress had the most significant impact on the expression of Pa CRKs,with the expression level of Pa CRK1upregulated 8-fold under salt stress.These results indicated that Pa CRK1 is involved in the plant’s response pathway to external environmental changes.Through analysis of the structural domains and subcellular localization of Pa CRK1,it was found that Pa CRK1 is a receptor-like kinase located on the cell membrane.In order to verify the function of Pa CRK1 under salt stress,this study overexpressed Pa CRK1 in Arabidopsis thaliana,and the results showed that Arabidopsis thaliana with Pa CRK1overexpressed grew significantly better than the wild type under salt stress.Pa CRK1was further overexpressed in the sweet cherry rootstock Gisela 5.The results showed that the phenotype of the overexpressing Pa CRK1 Gisela 5 line was better than that of the control under salt stress.Physiological and biochemical indicators indicated that overexpression of Pa CRK1 increased root activity and chlorophyll content.The accumulation of MDA and H2O2in the roots of transgenic lines were significantly reduced,while the content of Vc increased.Antioxidant enzyme activity detection and transcriptome analysis showed that Pa CRK1 enhanced salt tolerance of sweet cherry seedlings by upregulating the expression of antioxidant-related genes.This study has broadened our understanding of the application of plant receptor kinases,especially CRKs,in stress resistance.At the same time,it has provided necessary theoretical support for the screening of stress-resistant transgenic sweet cherries. |
