UvHOG1 is important for hyphal growth and stress responses in the rice false smut fungus Ustilaginoidea virens

Abstract

Rice false smut caused by Ustilaginoidea virens is one of the most important diseases of rice worldwide. Although its genome has been sequenced, to date there is no report on targeted gene deletion in U. virens and no molecular studies on genetic mechanisms regulating the infection processes of this destructive pathogen. In this study, we attempted to generate knockout mutants of the ortholog of yeast HOG1 MAP kinase gene in U. virens. One Uvhog1 deletion mutant was identified after screening over 600 hygromycin-resistant transformants generated by Agrobacterium tumefaciens mediated transformation. The Uvhog1 mutant was reduced in growth rate and conidiation but had increased sensitivities to SDS, Congo red, and hyperosmotic stress. Deletion of UvHOG1 resulted in reduced expression of the stress response-related genes UvATF1 and UvSKN7. In the Uvhog1 mutant, NaCl treatment failed to stimulate the accumulation of sorbitol and glycerol. In addition, the Uvhog1 mutant had reduced toxicity on shoot growth in rice seed germination assays. Overall, as the first report of targeted gene deletion mutant in U. virens, our results showed that UvHOG1 likely has conserved roles in regulating stress responses, hyphal growth, and possibly secondary metabolism.

Towards understanding the biosynthetic pathway for ustilaginoidin mycotoxins in Ustilaginoidea virens

“…PEG-mediated U. virens transformation was performed as described previously (Zheng et al, 2016). Briefly, the collected conidia were inoculated into 50 ml of PS medium and cultured with shaking at 28 C for 18-20 h. The hyphae were harvested by filtration with three layers of lens wiping paper, and were then rinsed with 1.2 M KCl.…”

“…UvPKS1 with the RP27 promoter was amplified from the constructed pKN plasmid with the primers C-RP27-F and C-UvPKS1-R and was then recombined into pY2P102 digested by EcoR I and Hind III using ClonExpress ® II One Step Cloning Kit. The resultant constructs were transformed into the respective mutant strains via PEG-mediated transformation (Zheng et al, 2016). The complementary strains were confirmed by western blot analyses.…”

Enhanced virulence of Fusarium species associated with spear rot of oil palm following recovery from osmotic stress

“…The osmoregulation MAPK pathway is well conserved in fungi. The inactivation of Hog1 orthologs increases sensitivity to osmotic stress and attenuates the virulence of Beauveria bassiana (Zhang et al 2009), Cryphonectria parasitica (Park et al 2004), Fusarium graminearum (Zheng et al 2012) and Metarhizium acridum (Jin et al 2012), and Ustilaginoidea virens (Zheng et al 2016). The osmoadaptative response of F. verticillioides is also coupled to the marked induction of FUM1 gene expression, a gene required for fumonisin biosynthesis (Marín et al 2010).…”

The essential effector SCRE1 in Ustilaginoidea virens suppresses rice immunity via a small peptide region

“…To create gene‐replacement mutants in U. virens , polyethylene glycol (PEG)‐mediated protoplast transformation was performed in combination with a modified CRISPR/Cas9 system (Zheng et al , ). Briefly, the protoplasts were prepared from the mycelia after being incubated in lysis buffer (25 g/L driselase, 10 g/L lysing enzymes and 0.05 g/L lyticase in 1.2 M KCl).…”