Evolutionary Expansion of WRKY Gene Family in Banana and Its Expression Profile during the Infection of Root Lesion Nematode, Pratylenchus coffeae

Abstract

The WRKY family of transcription factors orchestrate the reprogrammed expression of the complex network of defense genes at various biotic and abiotic stresses. Within the last 96 million years, three rounds of Musa polyploidization events had occurred from selective pressure causing duplication of MusaWRKYs with new activities. Here, we identified a total of 153 WRKY transcription factors available from the DH Pahang genome. Based on their phylogenetic relationship, the MusaWRKYs available with complete gene sequence were classified into the seven common WRKY sub-groups. Synteny analyses data revealed paralogous relationships, with 17 MusaWRKY gene pairs originating from the duplication events that had occurred within the Musa lineage. We also found 15 other MusaWRKY gene pairs originating from much older duplication events that had occurred along Arecales and Poales lineage of commelinids. Based on the synonymous and nonsynonymous substitution rates, the fate of duplicated MusaWRKY genes was predicted to have undergone sub-functionalization in which the duplicated gene copies retain a subset of the ancestral gene function. Also, to understand the regulatory roles of MusaWRKY during a biotic stress, Illumina sequencing was performed on resistant and susceptible cultivars during the infection of root lesion nematode, Pratylenchus coffeae. The differential WRKY gene expression analysis in nematode resistant and susceptible cultivars during challenged and unchallenged conditions had distinguished: 1) MusaWRKYs participating in general banana defense mechanism against P.coffeae common to both susceptible and resistant cultivars, 2) MusaWRKYs that may aid in the pathogen survival as suppressors of plant triggered immunity, 3) MusaWRKYs that may aid in the host defense as activators of plant triggered immunity and 4) cultivar specific MusaWRKY regulation. Mainly, MusaWRKY52, -69 and -92 are found to be P.coffeae specific and can act as activators or repressors in a defense pathway. Overall, this preliminary study in Musa provides the basis for understanding the evolution and regulatory mechanism of MusaWRKY during nematode stress.

Genome-wide investigation of WRKY gene family in pineapple: evolution and expression profiles during development and stress

“…Comparison of the number of WRKY genes in pineapple with other sequenced monocot genomes has shown that pineapple possesses comparatively lesser number of genes [ 34 , 43 – 45 ]. Tandem and segmental duplication events have played a critical role in the expansion of WRKY gene family [ 4 ].…”

Transcriptomic analysis of resistant and susceptible banana corms in response to infection by Fusarium oxysporum f. sp. cubense tropical race 4

“…The result was similar to a previous study which reported that defense was built up in a resistant coffee accession before leaf miner ( Leucoptera coffella ) attack 38 . Among the 3,867 DEGs, it is worth mentioning that the most enriched KEGG pathway belonged to plant-pathogen interaction and was composed on 7 WRKY transcription factors known to play an important role in biotic stress resistance 39–41 . Interestingly, 12 out of the 51 TIFY transcription factors contained in the banana genome were also differentially expressed.…”

“…In contrast, WRKY70 increased plant susceptibility to necrotrophic fungal pathogens because it acts as a repressor of jasmonate-regulated genes 71 . A total of 153 WRKY transcription factors were identified in the DH Pahang genome 25,41 . It was found that a large number (56) of WRKY genes showed inducible expression in banana root tissue during Foc infection 40 .…”

Functional Analysis of MaWRKY24 in Transcriptional Activation of Autophagy-Related Gene 8f/g and Plant Disease Susceptibility to Soil-Borne Fusarium oxysporum f. sp. cubense

“…Interesting, PtrWRKY18 (Populus trichocarpa, Ptr) and PtrWRKY35 activate pathogenesis-related (PR) genes, and increase the resistance to the biotrophic pathogen Melampsora [23]. In the banana, MaWRKY69 and MaWRKY92 are highly upregulated in the susceptible cultivar, but downregulated in the resistant cultivar after infection by the root lesion nematode Pratylenchus coffeae [24]. MaWRKY71-overexpressing transgenic bananas have increased salt and oxidative stress resistance compared to wild-type bananas, with no effect on the disease resistance against Foc [25].…”

“…A recent study showed that MaWRKY31, MaWRKY33, MaWRKY60, and MaWRKY71 directly bind to the W-box elements in the promoters of 9-cis-epoxycarotenoid dioxygenase 1 (MaNCED1) and MaNCED2 and activate their expression, thereby regulating abscisic acid-induced cold tolerance in banana fruit [27]. Although MaWRKYs are comprehensively identified in the banana, the in vivo roles remain elusive [9,24], and need to be investigated further.…”