Transcriptomics-based identification of <italic>WRKY</italic> genes and characterization of a salt and hormone-responsive <italic>PgWRKY1</italic> gene in <italic>Panax ginseng</italic>

Abstract

WRKY proteins belong to a transcription factor (TF) family and play dynamic roles in many plant processes, including plant responses to abiotic and biotic stresses, as well as secondary metabolism. However, no WRKY gene in Panax ginseng C.A. Meyer has been reported to date. In this study, a number of WRKY unigenes from methyl jasmonate (MeJA)-treated adventitious root transcriptome of this species were identified using next-generation sequencing technology. A total of 48 promising WRKY unigenes encoding WRKY proteins were obtained by eliminating wrong and incomplete open reading frame (ORF). Phylogenetic analysis reveals 48 WRKY TFs, including 11 Group I, 36 Group II, and 1 Group III. Moreover, one MeJA-responsive unigene designated as PgWRKY1 was cloned and characterized. It contains an entire ORF of 1077 bp and encodes a polypeptide of 358 amino acid residues. The PgWRKY1 protein contains a single WRKY domain consisting of a conserved amino acid sequence motif WRKYGQK and a C2H2-type zinc-finger motif belonging to WRKY subgroup II-d. Subcellular localization of PgWRKY1-GFP fusion protein in onion and tobacco epidermis cells revealed that PgWRKY1 was exclusively present in the nucleus. Quantitative real-time polymerase chain reaction analysis demonstrated that the expression of PgWRKY1 was relatively higher in roots and lateral roots compared with leaves, stems, and seeds. Importantly, PgWRKY1 expression was significantly induced by salicylic acid, abscisic acid, and NaCl, but downregulated by MeJA treatment. These results suggested that PgWRKY1 might be a multiple stress-inducible gene responding to hormones and salt stresses.

Both JrWRKY2 and JrWRKY7 of Juglans regia mediate responses to abiotic stresses and abscisic acid through formation of homodimers and interaction

“…This suggests that PgWRKY1 might be a multiple stress‐inducible gene that can respond to hormones and salt stress, and may also be important for root formation (Nuruzzaman et al . ). On the basis of these reports, we suggest, JrWRKY2 and JrWRKY7 are important candidate genes in abiotic stress responses, tissue formation and development.…”

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.…”

Research progress in terms of the biosynthesis and regulation of terpenoids from medicinal plants

“…达 玛烷合酶(dammarenediol synthase, DS)可催化2,3-氧化 鲨烯生成达玛烯二醇, 被认为是人参皂苷生物合成中 最重要的关键酶, Han等人 [36] 通过RNAi技术使DS基因 沉默, 导致人参根中皂苷含量降低至对照组的84.5%. 可响应SA, ABA和NaCl的正向调控, 表明其可能参与 人参的多个信号途径 [99] .…”