Abstract
BackgroundExpansin loosens plant cell walls and involves in cell enlargement and various abiotic stresses. Plant expansin superfamily contains four subfamilies: α-expansin (EXPA), β-expansin (EXPB), expansin-like A (EXLA), and expansin-like B (EXLB). In this work, we performed a comprehensive study on the molecular characterization, phylogenetic relationship and expression profiling of common wheat (Triticum aestivum) expansin gene family using the recently released wheat genome database (IWGSC RefSeq v1.1 with a coverage rate of 94%).ResultsGenome-wide analysis identified 241 expansin genes in the wheat genome, which were grouped into three subfamilies (EXPA, EXPB and EXLA) by phylogenetic tree. Molecular structure analysis showed that wheat expansin gene family showed high evolutionary conservation although some differences were present in different subfamilies. Some key amino acid sites that contribute to functional divergence, positive selection, and coevolution were detected. Evolutionary analysis revealed that wheat expansin gene superfamily underwent strong positive selection. The transcriptome map and qRT-PCR analysis found that wheat expansin genes had tissue/organ expression specificity and preference, and generally highly expressed in the roots. The expression levels of some expansin genes were significantly induced by NaCl and polyethylene glycol stresses, which was consistent with the differential distribution of the cis-elements in the promoter region.ConclusionsWheat expansin gene family showed high evolutionary conservation and wide range of functional divergence. Different selection constraints may influence the evolution of the three expansin subfamilies. The different expression patterns demonstrated that expansin genes could play important roles in plant growth and abiotic stress responses. This study provides new insights into the structures, evolution and functions of wheat expansin gene family.
Highlights
Expansin loosens plant cell walls and involves in cell enlargement and various abiotic stresses
This study identified 241 expansin genes from recently released wheat genome database, which were classified into EXPA, EXPB and expansin-like A (EXLA) subfamilies
Molecular characterization showed that wheat expansin gene family showed high evolutionary conservation
Summary
Expansin loosens plant cell walls and involves in cell enlargement and various abiotic stresses. We performed a comprehensive study on the molecular characterization, phylogenetic relationship and expression profiling of common wheat (Triticum aestivum) expansin gene family using the recently released wheat genome database (IWGSC RefSeq v1.1 with a coverage rate of 94%). Common wheat (Triticum aestivum L.) is one of the three most important grain crops worldwide, accounting for about 35% of the world's staple food. Wheat serves as an important protein source of human food. Hexaploid wheat contains A, B and D genomes with about 17 Gb in genome size, which was five times larger than that of humans [1]. Expansin genes were widely investigated in different plants, including oat coleoptiles [6], rice [7], cotton fiber [8], and soybean [9].
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