Cotton RSG2 Mediates Plant Resistance against Verticillium dahliae by miR482b Regulation

SIMPLE SUMMARY: Cotton is an important economic crop, but its production is constrained by various biotic and abiotic stresses. Verticillium wilt caused by Verticillium dahliae is a major factor limiting cotton yield, causing significant losses in both quantity and quality. In plant resistance research, miRNAs are considered important regulatory factors, and the miR482 family is closely related to plant resistance. Typically, this family can target NBS-LRR genes to participate in cotton’s defense response to Verticillium wilt, but the specific molecular mechanisms still need further study. This study revealed the mechanism of ghr-miR482b and its target gene GhRSG2 in cotton’s resistance to Verticillium wilt through molecular biology and biochemistry, providing new ideas and candidate genes for breeding cotton varieties resistant to Verticillium wilt and a reference for the disease-resistant breeding of other crops, thereby improving agricultural productivity, reducing pesticide use, and promoting sustainable agriculture. ABSTRACT: Cotton Verticillium wilt, mainly caused by Verticillium dahliae, has a serious impact on the yield and quality of cotton fiber. Many microRNAs (miRNAs) have been identified to participate in plant resistance to V. dahliae infection, but the exploration of miRNA’s function mechanism in plant defense is needed. Here, we demonstrate that the ghr-miR482b-GhRSG2 module mediates cotton plant resistance to V. dahliae infection. Based on the mRNA degradation data and GUS fusion experiments, ghr-miR482b directedly bonds to GhRSG2 mRNA to lead to its degradation. The knockdown and overexpression of ghr-miR482b through virus-induced gene silencing strategies enhanced (decreased by 0.39-fold in disease index compared with the control) and weakened (increased by 0.46-fold) the plant resistance to V. dahliae, respectively. In addition, silencing GhRSG2 significantly increased (increased by 0.93-fold in disease index) the plant sensitivity to V. dahliae compared with the control plants treated with empty vector. The expression levels of two SA-related disease genes, GhPR1 and GhPR2, significantly decreased in GhRSG2-silenced plants by 0.71 and 0.67 times, respectively, and in ghr-miR482b-overexpressed (OX) plants by 0.59 and 0.75 times, respectively, compared with the control, whereas the expression levels of GhPR1 and GhPR2 were significantly increased by 1.21 and 2.59 times, respectively, in ghr-miR482b knockdown (KD) plants. In sum, the ghr-miR482b-GhRSG2 module participates in the regulation of plant defense against V. dahliae by inducing the expression of PR1 and PR2 genes.