Rice WOX family gene identification and expression analysis of seeds germinated under stress

【Objective】To identify rice WOX family gene members and to analyze expression of seeds germinated under stress, so as to provide theoretical reference for exploring function of WOX family genes, mechanism, rice genetic improvement.【Method】WOX family genes were identified. Their phylogenetic evolution relation, physicochemical properties, gene structures, conserved domains, conserved motifs, cis-acting elements, and chromosomal localization were analyzed. Their temporal and spatial expression characteristics and expression patterns under abiotic stress during seed germination were determined through qRT-PCR.【Result】Thirteen rice WOX family gene members(OsWOX1-OsWOX13) were obtained from identification of PlantTFDB data base and they could be divided into 3 branches, in which only 1 belonged to ancient evolutionary branch and 6 intermediate evolutionary branch and 6 modern evolutionary branch. Thirteen genes of OsWOXs family distributed unevenly in chromosome No.1, 3, 4, 5, 7, 8, 11. The rest 5 chromosome did not contain genes from this family. Gene structure differed greatly, indicating WOX gene function had difference and diversity. Thirteen rice WOX proteins located in cell nucleus, with Homodomain superfamily conserved domains and 10 conserved motifs, in which Motif 1 and Motif 2 located in every protein's conserved functional domains. The promoter regions of OsWOXs genes contained more light response elements and defense stress response elements, and seed-specific response elements(RY-element) existed in OsWOX1, OsWOX9, OsWOX11 and OsWOX12 genes. The expression patterns of 13 OsWOXs genes were significantly different under rice seed germination and stress. The expression of OsWOX8 gene was high in germinating seeds and seedlings, the expression of OsWOX9 and OsWOX11 genes was high in germinating seeds and the expression of OsWOX2, OsWOX6 and OsWOX8 genes was high in seedlings. Under drought stress, the relative expression of OsWOX1, OsWOX2, OsWOX4 and OsWOX5 genes in seedlings were 15.0 times, 8.0 times, 3.9 times and 3.6 times higher than those in the control(CK) group, respectively, while the relative expression levels of OsWOX3, OsWOX4 and OsWOX7 genes in seeds were 87.2%, 86.9% and 97.8% lower than those in the CK group, respectively.【Conclusion】OsWOXs gene family members are relatively advanced in phylogeny compared to that in Arabidopsis thaliana and corn, and only OsWOX8 is retained as the only ancient branch. OsWOXs family genes contain lots of light response and stress response elements, which may be more involved in photosynthesis and stress response. OsWOXs gene showed abundant and diverse expression patterns of in rice seed germination, seedling stage and various abiotic stresses and OsWOX9 and OsWOX11 were the key genes regulating seed germination.