Abstract
The sclerotium is an important dormant body for many plant fungal pathogens. Here, we reported that a protein, named Ss-Sl2, is involved in sclerotial development of Sclerotinia sclerotiorum. Ss-Sl2 does not show significant homology with any protein of known function. Ss-Sl2 contains two putative PAN modules which were found in other proteins with diverse adhesion functions. Ss-Sl2 is a secreted protein, during the initial stage of sclerotial development, copious amounts of Ss-Sl2 are secreted and accumulated on the cell walls. The ability to maintain the cellular integrity of RNAi-mediated Ss-Sl2 silenced strains was reduced, but the hyphal growth and virulence of Ss-Sl2 silenced strains were not significantly different from the wild strain. Ss-Sl2 silenced strains could form interwoven hyphal masses at the initial stage of sclerotial development, but the interwoven hyphae could not consolidate and melanize. Hyphae in these interwoven bodies were thin-walled, and arranged loosely. Co-immunoprecipitation and yeast two-hybrid experiments showed that glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Woronin body major protein (Hex1) and elongation factor 1-alpha interact with Ss-Sl2. GAPDH-knockdown strains showed a similar phenotype in sclerotial development as Ss-Sl2 silenced strains. Hex1-knockdown strains showed similar impairment in maintenance of hyphal integrity as Ss-Sl2 silenced strains. The results suggested that Ss-Sl2 functions in both sclerotial development and cellular integrity of S. sclerotiorum.
Highlights
Sclerotinia sclerotiorum (Lib.) de Bary is a notorious necrotrophic fungal pathogen that belongs to the Family Sclerotiniaceae in the Order Helotiales, and with worldwide distribution
The above observations suggested that the Ss-Sl2D1 and Ss-Sl2D2 are homologous with the PAN module
In this research we identified a gene, named Ss-Sl2, which encodes a secretory protein that shows no homology with any known functional protein from S. sclerotiorum
Summary
Sclerotinia sclerotiorum (Lib.) de Bary is a notorious necrotrophic fungal pathogen that belongs to the Family Sclerotiniaceae in the Order Helotiales, and with worldwide distribution. This fungus may infect 450 plant species and subspecies in 75 families including many important crops, such as oilseed rape, sunflower, soybean, lettuce, celery and onion [1]. Sclerotinia sclerotiorum produces sclerotia, which are hard, asexual resting structure composed of compact vegetative hyphal cells. Apothecia may produce millions of airborne ascospores, which are the primary source of inocula in most Sclerotinia diseases [3,4]. Sclerotial development is an important process in the lifecycle of S. sclerotiorum
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