Abstract
Grafting can improve the resistance of watermelon to soil-borne diseases. However, the molecular mechanism of defense response is not completely understood. Herein, we used a proteomic approach to investigate the molecular basis involved in grafted watermelon leaf defense against Fusarium oxysporum f.sp. niveum (FON) infection. The bottle gourd rootstock-grafted (RG) watermelon seedlings were highly resistant to FON compared with self-grafted (SG) watermelon plants, with a disease incidence of 3.4 and 89%, respectively. Meanwhile, grafting significantly induced the activity of pathogenesis-related proteases under FON challenge. Proteins extracted from leaves of RG and SG under FON inoculation were analyzed using two-dimensional gel electrophoresis. Thirty-nine differentially accumulated proteins (DAPs) were identified and classified into 10 functional groups. Accordingly, protein biosynthetic and stress- and defense-related proteins play crucial roles in the enhancement of disease resistance of RG watermelon seedlings, compared with that of SG watermelon seedlings. Proteins involved in signal transduction positively regulated the defense process. Carbohydrate and energy metabolism and photosystem contributed to energy production in RG watermelon seedlings under FON infection. The disease resistance of RG watermelon seedlings may also be related to the improved scavenging capacity of reactive oxygen species (ROS). The expression profile of 10 randomly selected proteins was measured using quantitative real-time PCR, among which, 7 was consistent with the results of the proteomic analysis. The functional implications of these proteins in regulating grafted watermelon response against F. oxysporum are discussed.
Highlights
Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] is an important fruit crop and contributes 11.98% of the world fruit production (FAO, 2018)1
Plant growth was significantly influenced by bottle gourd rootstock grafting under FON infection
Pathogen infection leads to dramatic changes in the carbohydrate metabolism of the infected plant tissue that was supported in our work by the alteration of C metabolism-related proteins in grafted watermelon seedlings infected with FON
Summary
Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] is an important fruit crop and contributes 11.98% of the world fruit production (FAO, 2018). Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. Niveum (FON), is the most serious production-limiting disease in watermelon-growing areas all over the world (Zhang et al, 2015a). The watermelon reference genome (Guo et al, 2013) and the whole-genome resequencing (Guo et al, 2019) developed a series of potential genes resistant to Fusarium wilt. These results should be useful for further elucidating the mechanism of resistance to Fusarium wilt and in the development of molecular markers for breeding programs of watermelon
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