WRKY gene family of Licorice (Glycyrrhiza uralensis): identification and expression analysis in response to abiotic stress

WRKY transcription factors (TF) control a variety of biological processes in higher plants, including abiotic and biotic stress responses. WRKY genes have been identified and functionally characterized in many plant species during the past ten years, but despite this progress, few investigations have focused on this TF family in licorice (Glycyrrhiza uralensis Fisch.). This study identified 72 WRKY genes from the licorice genome and classified them into three groups. The gene structure analysis indicated that the GuWRKY genes contain from one to eight introns, with the majority having two introns and three exons. Conserved motif analysis identified the conserved WRKY domain in most GuWRKYs. Further analysis of the promoter region revealed that almost all GuWRKYs had plant hormone- or stress-responsive cis-regulatory elements, with differences in the number of elements among the groups. The role of 10 selected GuWRKYs in regulating abiotic stress responses was further explored via quantitative real-time PCR (qRT-PCR) after low-temperature (4 °C), salt (150 mmol·L−1 NaCl), drought (15% polyethylene glycol 6000) treatments at 3, 6, 12, and 24 h. Thus, our study of the WRKY gene family in licorice provides a basis for further research on the structure and function of WRKY genes.