Abstract
Bacterial wilt (BW) is a serious disease that affects eggplant (Solanum melongena) production. Although resistance to this disease has been reported, the underlying mechanism is unknown. In this study, we identified a NAC family transcription factor (SmNAC) from eggplant and characterized its expression, its localization at the tissue and subcellular levels, and its role in BW resistance. To this end, transgenic eggplant lines were generated in which the expression of SmNAC was constitutively up regulated or suppressed using RNAi. The results indicated that overexpression of SmNAC decreases resistance to BW. Moreover, SmNAC overexpression resulted in the reduced accumulation of the plant immune signaling molecule salicylic acid (SA) and reduced expression of ICS1 (a gene that encode isochorismate synthase 1, which is involved in SA biosynthesis). We propose that reduced SA content results in increased bacterial wilt susceptibility in the transgenic lines. Our results provide important new insights into the regulatory mechanisms of bacterial wilt resistance in eggplant.
Highlights
Bacterial wilt (BW) is a serious disease that affects eggplant (Solanum melongena) production
We describe the identification of a NAC transcription factor (SmNAC) from eggplant (Solanum melongena) based on RNA-seq data, and present data supporting its role in resistance to bacterial wilt (BW), a complex and devastating soil-borne vascular disease in plants caused by Ralstonia solanacearum
NAC transcription factors elicit a variety of biological functions in plant development, including the regulation of responses to abiotic or biotic stresses, and they can be broadly classified into two large groups, I and II, based on structural features[35]
Summary
Bacterial wilt (BW) is a serious disease that affects eggplant (Solanum melongena) production. We identified a NAC family transcription factor (SmNAC) from eggplant and characterized its expression, its localization at the tissue and subcellular levels, and its role in BW resistance To this end, transgenic eggplant lines were generated in which the expression of SmNAC was constitutively up regulated or suppressed using RNAi. The results indicated that overexpression of SmNAC decreases resistance to BW. NAC family proteins have an N-terminus containing a highly conserved and specific NAC domain[2] and were originally characterized and named for their sequence similarity to the petuniahybrida NAM (NO APICAL MERISTEM) and the Arabidopsis thaliana ATAF1, ATAF2, and CUC2 (CUP-SHAPED COTYLEDON) genes[2] They have been shown to play a variety of roles in plant growth and development, responses to abiotic and biotic stresses, and fruit maturation and to be components of hormone signal transduction pathways[3,4,5,6]. The expression of VSP1 and LOX2 was enhanced after ANAC019 and ANAC055 were overexpressed, and the double mutant (ANAC019 and ANAC055) exhibited reduced VSP1 and LOX2 expression and resistance to Botrytis cinerea[18]
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