Mitogen-Activated Protein Kinases SvPmk1 and SvMps1 Are Critical for Abiotic Stress Resistance, Development and Pathogenesis of Sclerotiophoma versabilis.

Mitogen-activated protein kinase (MAPK) signaling pathways are evolutionarily conserved in eukaryotes and modulate responses to both internal and external stimuli. Pmk1 and Mps MAPK pathways regulate stress tolerance, vegetative growth and cell wall integrity in Saccharomyces cerevisiae and Pyricularia oryzae. Here, we deployed genetic and cell biology strategies to investigate the roles of the orthologs of Pmk1 and Mps1 in Sclerotiophoma versabilis (herein referred to as SvPmk1 and SvMps1, respectively). Our results showed that SvPmk1 and SvMps1 are involved in hyphal development, asexual reproduction and pathogenesis in S. versabilis. We found that ∆Svpmk1 and ∆Svmps1 mutants have significantly reduced vegetative growths on PDA supplemented with osmotic stress-inducing agents, compared to the wild type, with ∆Svpmps1 being hypersensitive to hydrogen peroxide. The two mutants failed to produce pycnidia and have reduced pathogenicity on Pseudostellaria heterophylla. Unlike SvPmk1, SvMps1 was found to be indispensable for the fungal cell wall integrity. Confocal microscopic analyses revealed that SvPmk1 and SvMps1 are ubiquitously expressed in the cytosol and nucleus. Taken together, we demonstrate here that SvPmk1 and SvMps1 play critical roles in the stress resistance, development and pathogenesis of S. versabilis.

Long-Read Genome Sequence Resource of Ascochyta versabilis Causing Leaf Spot Disease in Pseudostellaria heterophylla.

Ascochyta versabilis is the fungal pathogen that causes the severe leaf spot disease of Pseudostellaria heterophylla (Miq.) Pax, a vital Chinese herbal plant. Here, we deployed PacBio single-molecule real-time long-read sequencing technology to generate a near-complete genome assembly for the A. versabilis KC1 strain and obtained a total of 9.80 Gb raw reads. These reads were processed into a 41.05 Mb genome assembly containing 95 contigs with N50 of 1.70 Mb and a maximum length of 3.93 Mb. A total of 10,457 gene models, of which 1,004 encode putatively secreted proteins, were identified in the genome. This high-quality genome assembly and gene annotation resource will facilitate the institution of functional genetic studies aimed at providing a better insight into the infection mechanisms of A. versabilis to support the development of effective control strategies for leaf spot disease of P. heterophylla.