Molecular Cloning and Expression Analysis of Eight PgWRKY Genes in Panax ginseng Responsive to Salt and Hormones

Abstract

Despite the importance of WRKY genes in plant physiological processes, little is known about their roles in Panax ginseng C.A. Meyer. Forty-eight unigenes on this species were previously reported as WRKY transcripts using the next-generation sequencing (NGS) technology. Subsequently, one gene that encodes PgWRKY1 protein belonging to subgroup II-d was cloned and functionally characterized. In this study, eight WRKY genes from the NGS-based transcriptome sequencing dataset designated as PgWRKY2-9 have been cloned and characterized. The genes encoding WRKY proteins were assigned to WRKY Group II (one subgroup II-c, four subgroup II-d, and three subgroup II-e) based on phylogenetic analysis. The cDNAs of the cloned PgWRKYs encode putative proteins ranging from 194 to 358 amino acid residues, each of which includes one WRKYGQK sequence motif and one C2H2-type zinc-finger motif. Quantitative real-time PCR (qRT-PCR) analysis demonstrated that the eight analyzed PgWRKY genes were expressed at different levels in various organs including leaves, roots, adventitious roots, stems, and seeds. Importantly, the transcription responses of these PgWRKYs to methyl jasmonate (MeJA) showed that PgWRKY2, PgWRKY3, PgWRKY4, PgWRKY5, PgWRKY6, and PgWRKY7 were downregulated by MeJA treatment, while PgWRKY8 and PgWRKY9 were upregulated to varying degrees. Moreover, the PgWRKY genes increased or decreased by salicylic acid (SA), abscisic acid (ABA), and NaCl treatments. The results suggest that the PgWRKYs may be multiple stress–inducible genes responding to both salt and hormones.

Abscisic Acid Regulates the 3-Hydroxy-3-methylglutaryl CoA Reductase Gene Promoter and Ginsenoside Production in Panax quinquefolium Hairy Root Cultures

“…It has been noted that increased activation of some genes and the biosynthesis of specific proteins may improve the adaptation of the plant to drought or salt-stress conditions. For example, in Panax sp., the expression of S-adenosyl-L-methionine synthetase, PgWRKY1,2,4,5,8,9, LHT-type plant amino acid-transporter, and MYB transcription factor is activated in response to ABA treatment [16,17,18,19,20]. Literature data also indicates that abscisic acid can regulate the biosynthesis of secondary metabolites.…”

Advances in ginsenoside biosynthesis and metabolic regulation

“…Nuruzzaman et al. obtained 48 transcription factors related to the ginsenoside synthesis by transcriptional sequencing of the adventitious roots treated with MJ, in which the transcription factors of WRKY1‐9 were identified. In addition, it was found that WRKY1‐9 had different expression levels in roots, stems, leaves, adventitious roots, and seeds.…”

The Overexpression of a Transcription Factor Gene VbWRKY32 Enhances the Cold Tolerance in Verbena bonariensis

“…Some genes, including WRKY transcription factors (TFs), are induced to help plants adapt to stresses by changing physiology and morphology. WRKY TFs were a valuable family which resisted abiotic stress, such as cold, NaCl, drought, salicylic acid, ethylene, abscisic acid, methyl jasmonate, and hydrogen peroxide (H 2 O 2 ) (Wang et al, 2013;Zhou et al, 2015;Xiu et al, 2016). The WRKY family comprised one or two DNA-binding domains consisted of 60 amino acid regions and the highly conservative sequence WRKYGQK at its N-terminus and a zinc-finger motif (Cx 4−5 Cx 22−23 HxH or Cx 7 Cx 23 HxC) at C-terminus (Eulgem et al, 2000;Rushton et al, 2010).…”