Host-Induced Gene Silencing of a Multifunction Gene Sscnd1 Enhances Plant Resistance Against Sclerotinia sclerotiorum.

Yijuan Ding,Wei Qian,Xinran Meng,Hongmei Liao,Mengquan Dong,Yangui Chen,Baoqin Yan,Huafang Wan

doi:10.3389/fmicb.2021.693334

Abstract

Sclerotinia sclerotiorum is a devastating necrotrophic fungal pathogen and has a substantial economic impact on crop production worldwide. Magnaporthe appressoria-specific (MAS) proteins have been suggested to be involved in the appressorium formation in Magnaporthe oryzae. Sscnd1, an MAS homolog gene, is highly induced at the early infection stage of S. sclerotiorum. Knock-down the expression of Sscnd1 gene severely reduced the virulence of S. sclerotiorum on intact rapeseed leaves, and their virulence was partially restored on wounded leaves. The Sscnd1 gene-silenced strains exhibited a defect in compound appressorium formation and cell integrity. The instantaneous silencing of Sscnd1 by tobacco rattle virus (TRV)-mediated host-induced gene silencing (HIGS) resulted in a significant reduction in disease development in tobacco. Three transgenic HIGS Arabidopsis lines displayed high levels of resistance to S. sclerotiorum and decreased Sscnd1 expression. Production of specific Sscnd1 siRNA in transgenic HIGS Arabidopsis lines was confirmed by stem-loop qRT-PCR. This study revealed that the compound appressorium-related gene Sscnd1 is required for cell integrity and full virulence in S. sclerotiorum and that Sclerotinia stem rot can be controlled by expressing the silencing constructs of Sscnd1 in host plants.

Highlights

Sclerotinia sclerotiorum (Lib.) de Bary is a well-known necrotrophic phytopathogenic fungus with a broad host range, including many economically important crops, such as oilseed rape (Brassica napus), sunflowers, soybeans, peanuts and lentils (Boland and Hall, 1994; Bolton et al, 2006)
To examine whether Sscnd1 is involved in the pathogenicity of S. sclerotiorum, the detached B. napus leaves were inoculated with agar plugs derived from the wild-type, empty vector strain and Sscnd1 gene-silenced strains, and we found that the lesion areas of B. napus leaves infected with Sicnd1-9 and Sicnd1-20 were reduced to 0.52- and 0.58-fold of the wild-type strain and to 0.53- and 0.59-fold of the empty vector strain, respectively (Figures 4A,B)
The Sscnd1 gene-silenced strains showed a drastic reduction in virulence and compound appressorium formation

Summary

Introduction

Sclerotinia sclerotiorum (Lib.) de Bary is a well-known necrotrophic phytopathogenic fungus with a broad host range, including many economically important crops, such as oilseed rape (Brassica napus), sunflowers, soybeans, peanuts and lentils (Boland and Hall, 1994; Bolton et al, 2006). To adhere to the host surface, the tips of its hyphae become swollen and extensive branch prior to penetration and develop a multicellular, melanin-rich hyphal penetration structure, called compound appressorium (Jamaux et al, 2007; Huang et al, 2008; Uloth et al, 2016). This formation of compound appressorium is essential for the process in which fungi penetrate the host cuticle and form infectious hyphae to spread horizontally beneath the host cuticle (Liang and Rollins, 2018).

Methods

Results

Conclusion