Transcriptome-Wide Identification of WRKY Transcription Factor and Functional Characterization of RgWRKY37 Involved in Acteoside Biosynthesis in Rehmannia glutinosa

Abstract

WRKYs play important roles in plant metabolism, but their regulation mechanism in <i>Rehmannia glutinosa</i> remains elusive. In this study, 37 putative WRKY transcription factors (TFs) with complete WRKY domain from <i>R. glutinosa</i> transcriptome sequence data were identified. Based on their conserved domains and zinc finger motif, the <i>R. glutinosa</i> WRKY TFs were divided into five groups. Structural feature analysis shows that the 37 RgWRKY proteins contain WRKYGQK/GKK domains and a C2H2/C2HC-type zinc finger structure. To identify the function of <i>RgWRKY</i> members involved in acteoside biosynthesis, transcriptional profiles of 37 <i>RgWRKYs</i> in hairy roots under salicylic acid (SA), methyl jasmonate (MeJA), and hydrogen peroxide (H₂O₂) treatments were systematically established using RNA-seq analysis. Based on the correlationship between the expression levels of <i>RgWRKY</i> genes and acteoside content, <i>RgWRKY7</i>, <i>RgWRKY23</i>, <i>RgWRKY34</i>, <i>RgWRKY35</i>, and <i>RgWRKY37</i> were suggested to be involved in acteoside biosynthesis in <i>R. glutinosa</i>, and <i>RgWRKY37</i> was selected for gene functional research. Overexpression of <i>RgWRKY37</i> increased the content of acteoside and total phenylethanoid glycosides (PhGs) in hairy roots and enhanced the transcript abundance of seven enzyme genes involved in the acteoside biosynthesis pathway. These results strongly suggest the involvement of the WRKY transcription factor in the regulation of acteoside biosynthesis.