Abstract
BackgroundTomato gray leaf spot caused by Stemphylium lycopersici (S. lycopersici) is a serious disease that can severely hinder tomato production. To date, only Sm has been reported to provide resistance against this disease, and the molecular mechanism underlying resistance to this disease in tomato remains unclear. To better understand the mechanism of tomato resistance to S. lycopersici, real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR)-based analysis, physiological indexes, microscopy observations and transgenic technology were used in this study.ResultsOur results showed that the expression of SlERF01 was strongly induced by S. lycopersici and by exogenous applications of the hormones salicylic acid (SA) and jasmonic acid (JA). Furthermore, overexpression of SlERF01 enhanced the hypersensitive response (HR) to S. lycopersici and elevated the expression of defense genes in tomato. Furthermore, the accumulation of lignin, callose and hydrogen peroxide (H2O2) increased in the transgenic lines after inoculation with S. lycopersici. Taken together, our results showed that SlERF01 played an indispensable role in multiple SA, JA and reactive oxygen species (ROS) signaling pathways to provide resistance to S. lycopersici invasion. Our findings also indicated that SlERF01 could activate the expression of the PR1 gene and enhance resistance to S. lycopersici.ConclusionsWe identified the SlERF01 gene, which encodes a novel tomato AP2/ERF transcription factor (TF). Functional analysis revealed that SlERF01 positively regulates tomato resistance to S. lycopersici. Our findings indicate that SlERF01 plays a key role in multiple SA, JA and ROS signaling pathways to provide resistance to invasion by S. lycopersici. The findings of this study not only help to better understand the mechanisms of response to pathogens but also enable targeted breeding strategies for tomato resistance to S. lycopersici.
Highlights
Tomato gray leaf spot caused by Stemphylium lycopersici (S. lycopersici) is a serious disease that can severely hinder tomato production
The phylogenetic analysis results showed that SlERF01 may encode a novel ERF protein that participates in the disease resistance response
The SlERF01::green fluorescent proteins (GFPs) fusion construct was subsequently transformed into the A. tumefaciens GV3101 strain, with an empty GFP vector serving as a negative control
Summary
Tomato gray leaf spot caused by Stemphylium lycopersici (S. lycopersici) is a serious disease that can severely hinder tomato production. The various defensive signaling responses include reactive oxygen species (ROS) bursts and callose and lignin accumulation and lead to localized cell and tissue death [6, 7], which is referred to as the hypersensitive response (HR), at the site of pathogenic invasion to limit pathogen growth [8,9,10]. As a chemically reactive molecule, hydrogen peroxide (H2O2) can induce the HR [14], which is associated with subsequent lignin and callose accumulation, limiting the growth of pathogens by strengthening cell walls. Systemic acquired resistance (SAR) is characterized by long-lasting, broad-spectrum effects [15]; these effects can be triggered by PTI- and ETImediated pathogen recognition and are related to the levels of salicylic acid (SA) in local cells and distant tissues. Previous studies have shown that the defense hormone SA plays an essential role in the SAR signaling pathway by inducing SAR-related gene expression via the regulatory protein NPR1 and a transcriptional coactivator [16]
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