Identification And Functional Analyses Of LRR ? Receptor-Like Protein Kinases In Maize

Receptor-like protein kinases(RLKs)play important roles in communications of cell to cell and cell to the surrounding environments.They coordinate the function of plant cells to control cell growth,cell division,plant morphogenesis and so on.There are more than 610 RLKs in Arabidopsis,among which the leucine-rich repeat receptor-like kinases(LRR-RLKs)form the largest subfamily,containing at least 223 members.Arabidopsis LRR II-RLK family consists of 14 members,and detailed studies have been performed for the SERK subfamily.SERKs play central roles in brassinosteroid signal transduction,plant innate immune responses,anther development,stomatal patterning and floral organ abscission.In addition,unpulished data of our laboratory have shown that SERKs also play an important role in embryo development.Researches on another LRR II-RLK subfamily that was named as CIK(CLV3 INSENSITIVE RECEPTOR KINASE)by our laboratory revealed that CIKs have an important function in regulating the homeostasis of Arabidopsis shoot apical meristem(SAM).Maize,as an important crop,forage and industrial material,has an important position in the national economy.However,functions of LRR II-RLKs in maize are largely unknown.In this work,17 putative maize LRR II-RLKs were identified in NCBI database.Fourteen of these LRR II-RLK genes were cloned with the help of the Gateway technology and transformed into the weak BR receptor mutant bri1-5,the embryo development mutant serk1 serk2 serk3,and the weak SAM mutant cik1/2/4 to identify those that can suppress the phenotypes of the mutants.Three maize LRR II-RLK genes,Zm-8,Zm-16 and Zm-17,were found by phenotypic analysis of transgenic plants,which can suppress the phenotype of bri1-5,producing higher transgenic plants with flatter leaves and elongated petioles compared.They were also able to partially restore the embryo phenotype of serk1 serk2 serk3,showing significantly elongated cotyledons and hypocotyls in transgenic embryos.These results indicated that Zm-8,Zm-16,and Zm-17 have similar functions to AtSERKs.We also found that Zm-7,Zm-9,Zm-11 and Zm-13 can suppress the defective meristem of cik1/2/4,and the roots of the rescued transgenic plants are sensitive to exogenously applied CLV3 peptide,suggesting that at least these four genes in maize play functions similar to AtCIKs.All together,these results indicated that the LRR II-RLK genes of monocotyledonous maize and dicotyledonous Arabidopsis are functionally conserved.Arabidopsis SERKs and CIKs play important roles in various biological processes of growth,development,and responses to environmental cues,which suggests that their homologues in maize may also play similar important roles.This study provides a basis for the subsequent functional analysis of SERKs and CIKs in maize.