Rice Receptor-like Cytoplasmic Kinase STRK1 Is Involved In ABA Signaling Response

The plant hormone Abscisic acid（ABA）plays an important role in many processes of plant growth and development,including seed maturation,seed dormancy,stomatal closure,and seedling growth.ABA also plays an important role in plant responses to abiotic stresses such as cold,drought and salt.Receptor-like cytoplasmic kinase-mediated signal transduction is an important regulatory mechanism for plant growth and development in response to different environmental stresses.A previous study in our laboratory identified a receptor-like cytoplasmic kinase STRK1 from rice（Oryza sativa L.）that activates Cat C by phosphorylation of Tyr210 and modulates H₂O₂homeostasis to enhance salt and oxidative stress tolerance.ABA is an important hormone regulating salt stress response,and its signal transduction mechanism has been well studied,but the receptor-like cytoplasmic kinases involved in its signaling pathway are rarely reported.This study preliminarily explored the molecular mechanism of STRK1 involved in ABA signal transduction to regulate salt stress response of rice.The main results are as follows:（1）STRK1 is involved in ABA signal response.Expression profile analysis showed that STRK1 expression was induced by ABA.ABA sensitivity analysis showed that compared with the wild type,strk1 knockout plants were less sensitive to ABA,while STRK1 overexpressed plants were more sensitive to ABA,suggesting that STRK1 could enhance the sensitivity of rice seedlings to ABA.The expression levels of genes related to ABA synthesis were detected and STRK1 affected the expression levels of some GENES related to ABA synthesis.Overexpression of STRK1 up-regulated the expression of OsCat B,OsSod Cc2 and ABA-dependent stress genes,while deletion of STRK1 down-regulated the expression of related genes.These results suggest that STRK1may be involved in ABA signal transduction by influencing ABA-dependent stress responses.（2）STRK1 interacts with OsABIL2 in cell membrane.Phosphorylation at the tyrosine site of At ABI1,A member of PP2Cs A subgroup,was found in the ABA signaling pathway.The homology of OsABIL2 and At ABI1 in rice was the highest.OsABIL2 was cloned from rice,and the interaction between STRK1and OsABIL2 in vitro and in vivo was further verified by yeast two-hybrid、GST-Pull down and BiFC experiments.（3）STRK1 may be involved in ABA signal response through interaction with OsABIL2.Using bioinformatics website analysis gene structure and expression pattern of time and space,found that OsABIL2 contains 4 exons and3 introns,and has the highest expression level in vegetative stage and leaves.Subcellular localization analysis showed that OsABIL2 was localized to the cell membrane,consistent with the subcellular localization of STRK1 and OsABIL2-STRK1 interaction.Then,OsABIL2 overexpression and knockout vectors were constructed,and three OsABIL2 overexpression lines,one homozygous knockout line abil2 and several heterozygous lines were obtained by agrobacterium tumefaciens transformation and identification.Related phenotypes and physiological traits need to be analyzed.In conclusion,this study preliminarily proved that STRK1 is involved in ABA signal response,and speculated that STRK1 may be involved in the regulation of ABA signal transduction through its interaction with OsABIL2 on the cell membrane.In addition,rice genetic material related to STRK1 and OsABIL2 was constructed,which laid a foundation for further analysis of STRK1’s involvement in ABA signal transduction regulation.