Abstract
WRKY transcription factors play significant roles in plant stress responses. In this study, a class III WRKY gene ScWRKY5, was successfully isolated from sugarcane variety ROC22. The ScWRKY5 was a nucleus protein with transcriptional activation activity. The ScWRKY5 gene was constitutively expressed in all the sugarcane tissues, with the highest expression level in the stem epidermis and the lowest in the root. After inoculation with Sporisorium scitamineum for 1 d, the expression level of ScWRKY5 was significantly increased in two smut-resistant varieties (YZ01-1413 and LC05-136), while it was decreased in three smut-susceptible varieties (ROC22, YZ03-103, and FN40). Besides, the expression level of ScWRKY5 was increased by the plant hormones salicylic acid (SA) and abscisic acid (ABA), as well as the abiotic factors polyethylene glycol (PEG) and sodium chloride (NaCl). Transient overexpression of the ScWRKY5 gene enhanced the resistance of Nicotiana benthamiana to the tobacco bacterial pathogen Ralstonia solanacearum, however the transiently overexpressed N. benthamiana was more sensitive to the tobacco fungal pathogen Fusarium solani var. coeruleum. These results provide a reference for further research on the resistance function of sugarcane WRKY genes.
Highlights
WRKY transcription factors play significant roles in plant stress responses
Phylogenetic tree analysis showed that ScWRKY5 and the WRKY family proteins from S. spontaneum could be divided into three categories (I–III) (Fig. S1)
There were some elements related to the abiotic stress response, such as MBS cis-acting elements involved in drought stress
Summary
WRKY transcription factors play significant roles in plant stress responses. Through the expression changes of various stress-related functional genes, the transcripts are recombined in plants to enhance adaptability to the environment. The most typical feature of WRKY transcription factors is that there is a polypeptide sequence of at least 60 amino acids in length in the DNA-binding domain of WRKY family members. Type I WRKYs contain two WRKY domains and a zinc-finger-like motif C 2H2 (CX4-5CX22 -23HX1H) (X represents any amino acid residue). Type II WRKYs contain only one WRKY domain, and their zinc-finger-like motif is the same as the type I WRKYs. According to the homology between family members, type II WRKYs can be further divided into five subclasses (IIa–IIe)[12], while, Dong et al.[19] divided the type II WRKYs of A. thaliana into seven subclasses (IIa–IIg). 58 WRKYs were induced by drought s tress[27]
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