Identification and expression analysis of VQ gene family in barley

【Objective】 In this study, gene family members of VQ in barley were identified expression analysis was conducted, which provided theoretical basis for functional mining of barley VQ gene.【Method】 In this study, the VQ gene was identified from the barley, and its structural features and coding protein sequences were analyzed using a bioinformatics approach. Barley tissue expression patterns, salt stress and biotic stress were analyzed based on transcriptome sequencing data and real-time fluorescent quantitative PCR(qRT-PCR).【Result】 A total of 29 HvVQ genes(HvVQ1-HvVQ29) were identified in the barley genome.The average length of HvVQ protein sequences was short(214 aa), most HvVQ proteins were basic or neutral, and HvVQ genes were unevenly distributed on the chromosomes of barley and localized in the nucleus. All 29 HvVQ proteins contained the conserved motif FxxxVQxhTG, and nearly 90% HvVQ genes have no introns. Phylogenetic analysis were classified the VQ family genes of barley, Arabidopsis and rice into 7 subfamilies (Ⅰ-Ⅶ), and HvVQs genes was unevenly distributed in subfamilies Ⅱ-Ⅶ. Interspecies covariance analysis showed that the number of covariate gene pairs with rice(17 pairs) was much higher than that with Arabidopsis(1 pair), and intraspecies covariance analysis found 1 covariate gene pair. Nonsynonymous substitution rate/synonymous substitution rate(Ka/Ks) calculations revealed that HvVQ proteins were mainly in the purifying selection state. The promoter region of the HvVQ genes was rich in growth and developmental elements, abiotic stress-responsive elements, and hormone-responsive elements, with a diversity of species and distribution. Predictive analysis of the protein network inferred that it interacted with two subfamilies of HvWRKYs(II-c and III). Most of the HvVQ genes were expressed in tissues, and HvVQ19 expression was up-regulated when subjected to salt stress, the expression levels in the root tip and root elongation regions were up-regulated by 1.40 and 1.10 times respectively. qRT-PCR was performed on 10 of the HvVQ genes, of which HvVQ2 gene was significantly down-regulated under both aphid and yellow dwarf virus stresses(fold change <0.5 for significant repression and >2.0 for significant induction), HvVQ7 and HvVQ15 genes were the most significantly up-regulated under aphid and yellow dwarf virus stresses, and the other 7 HvVQ genes all showed differential expression.【Conclusion】 HvVQ gene family members are conserved and evolved in sequence, their expression is tissue specific, most members expression levels are regulated by salt stress, have a large number of hormone response elements, and are presumed to play important regulatory roles in biotic and abiotic stresses.