Abstract
Sclerotinia sclerotiorum is one of the most devastating pathogens in Brassica napus and causes huge economic loss worldwide. Though around one hundred putative effectors have been predicted in Sclerotinia sclerotiorum genome, their functions are largely unknown. In this study, we cloned and characterized a novel effector, SsERP1 (ethylene pathway repressor protein 1), in Sclerotinia sclerotiorum. SsERP1 is a secretory protein highly expressed at the early stages of Sclerotinia sclerotiorum infection. Ectopic overexpression of SsERP1 in plant leaves promoted Sclerotinia sclerotiorum infection, and the knockout mutants of SsERP1 showed reduced pathogenicity but retained normal mycelial growth and sclerotium formation, suggesting that SsERP1 specifically contributes to the pathogenesis of Sclerotinia sclerotiorum. Transcriptome analysis indicated that SsERP1 promotes Sclerotinia sclerotiorum infection by inhibiting plant ethylene signaling pathway. Moreover, we showed that knocking down SsERP1 by in vitro synthesized double-strand RNAs was able to effectively inhibit Sclerotinia sclerotiorum infection, which verifies the function of SsERP1 in Sclerotinia sclerotiorum pathogenesis and further suggests a potential strategy for Sclerotinia disease control.
Highlights
To identify the putative effectors of S. sclerotiorum, we carried out a bioinformatical screening using the following criteria: (1) contain secretory signal peptide, (2) have increased expression during S. sclerotiorum infection, and (3) do not harbor cell wall degrading enzyme-like domains, according to the data available in public databases or literatures [14,25]
TMHMM 2.0 analysis found no transmembrane domain in SsERP1 (Figure S2)
We cloned and characterized a novel effector of S. sclerotiorum, SsERP1, a secretory protein that is highly expressed in the early stages of S. sclerotiorum infection
Summary
Brassica napus is one of the most important oil crops and contributes a considerable proportion of the world’s edible vegetable oil [1,2]. The quality and yield of rapeseed are seriously threatened by Sclerotinia disease caused by Sclerotinia sclerotiorum, a typical necrotrophic plant pathogen with a broad host range [3]. In addition to B. napus, S. sclerotiorum infects many other agronomically important crops, such as soybean and sunflower [4]. No genetic source of complete resistance to S. sclerotiorum has been reported within Brassica species [3,5], which hampered the creation of resistant cultivars by hybrid breeding. Deciphering the mechanisms of S. sclerotiorum pathogenesis is crucial for developing new effective and environment friendly methods to control
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