Abstract
Members of the large family of WRKY transcription factors are involved in a wide range of developmental and physiological processes, most particularly in the plant response to biotic and abiotic stress. Here, an analysis of the soybean genome sequence allowed the identification of the full complement of 188 soybean WRKY genes. Phylogenetic analysis revealed that soybean WRKY genes were classified into three major groups (I, II, III), with the second group further categorized into five subgroups (IIa–IIe). The soybean WRKYs from each group shared similar gene structures and motif compositions. The location of the GmWRKYs was dispersed over all 20 soybean chromosomes. The whole genome duplication appeared to have contributed significantly to the expansion of the family. Expression analysis by RNA-seq indicated that in soybean root, 66 of the genes responded rapidly and transiently to the imposition of salt stress, all but one being up-regulated. While in aerial part, 49 GmWRKYs responded, all but two being down-regulated. RT-qPCR analysis showed that in the whole soybean plant, 66 GmWRKYs exhibited distinct expression patterns in response to salt stress, of which 12 showed no significant change, 35 were decreased, while 19 were induced. The data present here provide critical clues for further functional studies of WRKY gene in soybean salt tolerance.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-2647-x) contains supplementary material, which is available to authorized users.
Highlights
Soybean (Glycine max) is a global cash crop
Our findings provide new clues for further investigation of WRKY gene in soybean salt tolerance
The acquisition of full genome sequences has simplified the enumeration of WRKY copy number, so that it is clear that there are 81 WRKY copies in tomato (Huang et al 2012), 55 in cucumber (Ling et al 2011), 104 in poplar (He et al 2012), 59 in grapevine (Wang et al 2014), 116 in cotton (Dou et al 2014) and 119 in maize (Wei et al 2012)
Summary
Soybean (Glycine max) is a global cash crop. Apart from its major contribution to human and animal nutrition, the seed provides a feedstock for biodiesel production and represents a significant raw material for a number of pharmaceutical and industrial processes (Phang et al 2008; Wang et al 2010). During the long period of evolution, soybean has evolved complex strategies to survive salt stress. These strategies are originated from the changes of various aspects, such as the genome, gene expression, metabolism and physiology (Phang et al 2008). Functionally reported salt tolerance related genes in soybean are mainly categorized into several classes, including ion transporter coding genes (e.g. GmHKT1, GmSALT3, GmNHX1, GmCAX1 and GmCHX1) (Chen et al 2011; Guan et al 2014; Li et al 2006; Luo et al 2005a; Qi et al 2014), transcription factors (TFs) (e.g. GmNAC11/-20/-29, GmDREB1, GmMYB76/-92/-174/-177, GmbZIP44/-62/-78, GmWRKY27 and GmERF7) (Hao et al 2011; Jin et al 2010; Liao et al 2008a, b; Wang et al 2015; Zhai et al 2013) and others genes (e.g. glutathione S-transferase gene GsGST, late embryogenesis abundant gene GmLEA, calcineurin B-like protein coding gene GmCBL1 and flavone synthase gene GmFNSII) (Ji et al 2010; Lan et al 2005; Li et al 2012; Phang et al 2008; Wang et al 2011; Yan et al 2014; Zhou et al 2010)
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