Identification and expression analysis of WRKY family genes under biotic and abiotic stresses in Brassica rapa

Abstract

WRKY proteins constitute one of the largest transcription factor families in higher plants, and they are involved in multiple biological processes such as plant development, metabolism, and responses to biotic and abiotic stresses. Genes of this family have been well documented in response to many abiotic and biotic stresses in many plant species, but not yet against Pectobacterium carotovorum subsp. carotovorum and Fusarium oxysporum f.sp. conglutinans in any of the plants. Moreover, potentiality of a specific gene may vary depending on stress conditions and genotypes. To identify stress resistance-related potential WRKY genes of Brassica rapa, we analyzed their expressions against above-mentioned pathogens and cold, salt, and drought stresses in B. rapa. Stress resistance-related functions of all Brassica rapa WRKY (BrWRKY) genes were firstly analyzed through homology study with existing biotic and abiotic stress resistance-related WRKY genes of other plant species and found a high degree of homology. We then identified all BrWRKY genes in a Br135K microarray dataset, which was created by applying low-temperature stresses to two contrasting Chinese cabbage doubled haploid (DH) lines, Chiifu and Kenshin, and selected 41 BrWRKY genes with high and differential transcript abundance levels. These selected genes were further investigated under cold, salt, and drought stresses as well as after infection with P. carotovorum subsp. carotovorum and F. oxysporum f.sp. conglutinans in B. rapa. The selected genes showed an organ-specific expression, and 22 BrWRKY genes were differentially expressed in Chiifu compared to Kenshin under cold and drought stresses. Six BrWRKY genes were more responsive in Kenshin compared to Chiffu under salt stress. In addition, eight BrWRKY genes showed differential expression after P. carotovorum subsp. carotovorum infection and five genes after F. oxysporum f.sp. conglutinans infection in B. rapa. Thus, the differentially expressed BrWRKY genes might be potential resources for molecular breeding of Brassica crops against abiotic and biotic stresses and several genes, which showed differential expressions commonly in response to several stresses, might be useful for multiple stress resistance. These findings would also be helpful in resolving the complex regulatory mechanism of WRKY genes in stress resistance and for this further functional genomics study of these potential genes in different Brassica crops is essential.

BrWRKY65, a WRKY Transcription Factor, Is Involved in Regulating Three Leaf Senescence-Associated Genes in Chinese Flowering Cabbage

“…Although 145 WRKY TFs are found in Brassica rapa plants such as Chinese cabbage [34,35], and a senescence-related Group IIc WRKY TF BrWRKY75 is preliminarily characterized in our previous study [36], the mechanism(s) of senescence-associated WRKY TFs involved in regulating leaf senescence in Chinese flowering cabbage remains unclear. However, in the present work, searching our RNA-seq transcriptome database, a full-length WRKY gene (NP_001306245.1) showed increased expression during postharvest cabbage leaf senescence.…”

Genome-wide analysis of WRKY gene family in the sesame genome and identification of the WRKY genes involved in responses to abiotic stresses

“…Recent research has demonstrated that WRKY genes are involved in responses to various stresses and there is now compelling evidence that WRKYs are plant transcription factors that regulate tolerance to abiotic stresses [48]. Gene expression studies have shown that 20 AtWRKY genes in Arabidopsis, 41 OsWRKY genes in rice, 66 GmWRKY genes in soybean, 41 BrWRKY genes in Brassica rapa, and 74 BnWRKY genes in rapeseed are involved in responses to abiotic stresses [14,18,34,[49][50][51]. In this study, 44 SiWRKY genes were expressed differentially in response to waterlogging and drought stresses, indicating that these genes may also be involved in responses to abiotic stresses.…”

The chaperone MeHSP90 recruits MeWRKY20 and MeCatalase1 to regulate drought stress resistance in cassava

“…In our previous study, we identified 85 MeWRKYs and analyzed their expression profiles in response to various abiotic stresses (Wei et al, 2016b). Current studies have indicated that WRKY TFs are widely involved in regulating plant abiotic stress responses, such as drought, salt stress, and ABA signaling (Rushton et al, 2012;Liu et al, 2014;Gong et al, 2015;Kayum et al, 2015;Singh & Laxmi, 2015;He et al, 2016). As a WRKY TF, abscisic acid (ABA) overly sensitive 3 (ABO3) modulates ABA-mediated stomatal closure and drought stress resistance in Arabidopsis (Ren et al, 2010).…”