Comprehensive analysis for GRF and GIF genes and their responses to abiotic stresses in tea plant

GRFs and GIFs are important regulators in growth and development and in response to various abiotic stresses. Fifteen GRFs and five GIFs were identified from tea plant and divided into three and two groups according to phylogenetic analysis, respectively. All of CsGRF family members contained WRC and QLQ domains. Interestingly, dual WRC domains were found in CsGRF01. All of CsGIF family members harbored SNH and QG domains. All of 15 CsGRF genes were predicted to be targeted by csn-miR396b, implying strong post-transcriptional regulation. Fifteen CsGRFs and five CsGIFs were unevenly distributed on the chromosomes of tea plant. Two duplicated CsGIF gene pairs were identified with segmental duplication. One set of triplicated genes CsGRF04/06/07 were found in the tea plant genome. There were no tandem duplication events. The evolutionary analysis showed that these duplicated genes came across purification selection during the evolutionary period, implying conserved evolution. Moreover, eight pairs of orthologous GRF genes, two pairs of orthologous GIF genes between tea plant and Arabidopsis and six pairs of orthologous GRF genes between tea plant and rice were identified. The expression patterns showed that most CsGRFs and more than half of CsGIFs were highly expressed in bud. Co-expression analysis revealed that CsGIF05, CsGIF04 and CsGIF03 exhibited correlation with all of 15 CsGRFs in expression in diverse tissues or during all stages of leaf development. The expression levels of most CsGRFs and more than half of CsGIF genes were down-regulated in response to drought stress or salt stress. CsGIF05 and CsGIF04 exhibited correlation with all of 15 CsGRFs in expression under drought or salt stress condition. Protein interaction prediction showed that CsGIF05 was predicted to have interaction relationship with eight CsGRFs. These results revealed that CsGRFs and CsGIFs played crucial roles not only in growth and development but also in various abiotic stress responses, and they may play important roles in coordinating growth with stress responses by interaction in tea plant. It will provide important scientific basis for further researching the potential functions of CsGRFs and CsGIFs in response to abiotic stresses in tea plant.