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

Abstract

WRKYs play important roles in plant development and stress responses. Although MaWRKYs have been comprehensively identified in the banana (Musa acuminata), their in vivo roles and direct targets remain elusive. In this study, a transcript profile analysis indicated the common regulation of MaWRKYs transcripts in response to fungal pathogen Fusarium oxysporum f. sp. cubense (Foc). Among these MaWRKYs, MaWRKY24 was chosen for further analysis due to its higher expression in response to Foc. The specific nucleus subcellular location and transcription activated activity on W-box indicated that MaWRKY24 was a transcription factor. The correlation analysis of gene expression indicated that MaWRKYs were closely related to autophagy-associated genes (MaATG8s). Further analysis showed that MaWRKY24 directly regulated the transcriptional level of MaATG8f/g through binding to W-box in their promoters, as evidenced by quantitative real-time Polymerase Chain Reaction (PCR), dual luciferase assay, and electrophoretic mobility shift assay. In addition, overexpression of MaWRKY24 and MaATG8f/g resulted in disease susceptibility to Foc, which might be related to the activation of autophagic activity. This study highlights the positive regulation of MaWRKY24 in transcriptional activation of autophagy-related gene 8f/g in the banana and their common roles in disease susceptibility to soil-borne Foc, indicating the effects of MaWRKY24 on autophagy and disease susceptibility.

The Banana MaWRKY18, MaWRKY45, MaWRKY60 and MaWRKY70 Genes Encode Functional Transcription Factors and Display Differential Expression in Response to Defense Phytohormones

“…We also found NLS sites in all four banana WRKY proteins considered in this study and confirmed that these proteins were indeed localized in the nuclei of onion epidermal cells. These results are consistent with the nuclear localization of other plant WRKY TFs, including the banana WRKYs reported thus far [ 48 , 49 , 50 , 51 , 55 ]. Furthermore, we demonstrated that these four banana WRKYs were functional transcription factors in yeast since all of them were capable of activating RNA polymerase II for the transcription of three marker genes.…”

“…Despite these advances in WRKY gene annotations, only a small percentage of them have been functionally characterized, mainly in the model plants Arabidopsis and rice. In the case of economically important fruit crops, such as banana, with 164 WRKY genes annotated [ 29 ], only a few WRKY genes have been validated as TFs [ 48 , 49 , 50 , 51 ]. Cloning and elucidating the functional aspects of banana WRKY genes will expand our understanding of the multiple roles of these transcription factors and provide novel tools for genetic improvement.…”

“…Furthermore, we demonstrated that these four banana WRKYs were functional transcription factors in yeast since all of them were capable of activating RNA polymerase II for the transcription of three marker genes. Less than 5% of the WRKY genes found in the banana genome have been experimentally validated as TFs, and most of them are from the cultivar Cavendish [ 48 , 49 , 50 , 51 ]; this is the first report that assessed the transactivation activity of WRKY proteins from a wild banana ( M. acuminata ssp. malaccensis ), which is resistant to the most destructive diseases of this crop and is a progenitor of most banana cultivars [ 26 ].…”

Transcriptional Regulation of Drought Response in Arabidopsis and Woody Plants

“…Overexpression of PbrWRKY53 increased drought tolerance in tobacco and Pyrus ussuriensis , whereas the PbrWRKY53 knock-down lines showed compromised drought tolerance in P. ussuriensis with reduced PbrNCED1 and PbrNCED3 expression levels ( Liu Y. et al, 2019 ; Table 1 ). The function of WRKY TFs in biotic stress response has been well-studied in woody plants ( Duan et al, 2015 ; Jiang et al, 2017 ; Liu G. et al, 2019 ). However, their function in abiotic stress response, especially in drought response, needs to be deeply investigated.…”

Overexpression of Banana ATG8f Modulates Drought Stress Resistance in Arabidopsis

“…The recombinant plasmid pEGAD-MaATG8f (PromoterCaMV35S::GFP-MaATG8f ) has been described previously [44,46]. Briefly, the sequence of MaATG8f was cloned into pEGAD vector in the C-terminal in frame with green fluorescent protein (GFP) to form the constructs of PromoterCaMV35S::GFP-MaATG8s.…”