Genome-Wide Analysis of WRKY Genes and Their Response to Hormone and Mechanic Stresses in Carrot

Abstract

The <i>WRKY</i> gene family plays a vital role in plant development and environment response. Although previous studies suggested that the <i>WRKY</i> genes in carrot (Kuroda type) involved in biotic and abiotic stress responses, the information of <i>WRKY</i> genes in the latest version of the carrot genome (<i>Daucus carota</i> v2.0, Nantes type carrot) and their response to hormone and injury stresses have not been reported. In this study, we performed a genome-wide analysis of <i>WRKY</i>s using a chromosome-scale genome assembly of carrot (<i>Daucus carota</i> subsp. <i>sativus</i> L.). We identified a total of 67 <i>WRKY</i> genes, which were further classified into the three groups. These <i>WRKY</i> genes are unevenly distributed on carrot chromosomes. We found that more than half of them were derived from whole-genome duplication (WGD) events, suggesting that WGDs have played a major role during the evolution of the <i>WRKY</i> gene family. We experimentally ascertained the expression divergence existed between WGD-derived <i>WRKY</i> duplicated gene pairs, which is indicative of functional differentiation between duplicated genes. Our analysis of <i>cis</i>-acting elements indicated that <i>WRKY</i> genes were transcriptionally regulated upon hormone and mechanic injury stresses. Gene expression analyses by qRT-PCR further presented that <i>WRKY</i> genes were involved in hormone and mechanic injury stresses.