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

Zheng D, Wang Y, Han Y, Xu JR, Wang C - Sci Rep (2016)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.

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.

No MeSH data available.


Related in: MedlinePlus

Growth and conidium germination of the Uvhog1 mutant in the presence of different stresses.(A) The wild-type strain UV-8b, Uvhog1 mutant, and complementary transformant were cultured on YT medium with or without 0.5 M NaCl, 0.07% H2O2, 0.03% SDS (w/v), and 70 μg/ml Congo red. Photographs were taken after incubation at 25 °C for 14 days. (B) Conidia of UV-8b and the Uvhog1 mutant were incubated in YTS with 0.3 M NaCl for 16, 20, or 24 h. Bar = 20 μm.
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f2: Growth and conidium germination of the Uvhog1 mutant in the presence of different stresses.(A) The wild-type strain UV-8b, Uvhog1 mutant, and complementary transformant were cultured on YT medium with or without 0.5 M NaCl, 0.07% H2O2, 0.03% SDS (w/v), and 70 μg/ml Congo red. Photographs were taken after incubation at 25 °C for 14 days. (B) Conidia of UV-8b and the Uvhog1 mutant were incubated in YTS with 0.3 M NaCl for 16, 20, or 24 h. Bar = 20 μm.

Mentions: Because the HOG pathway is well conserved in fungi for responses to hyperosmotic stress1718, we assayed the defects of the Uvhog1 mutant in growth on YT medium with 0.5 M NaCl or 1 M sorbitol. In the presence of 0.5 M NaCl, the Uvhog1 mutant had no obvious growth after incubation for 14 days (Fig. 2A). Under the same conditions, the wild type was reduced in growth rate but still formed compact colonies (Fig. 2A; Table 2). We also assayed the effect of hyperosmotic stress on conidium germination. In the presence of 0.3 M NaCl, most of the wild-type conidia (72.1 ± 1.9%) germinated after incubation in YTS medium for 16 h but only 3.2 ± 1.3% mutant conidia germinated. Even after incubation for 24 h, only 5.0 ± 0.8% conidia produced germ tubes. Moreover, germ tube growth was stunted by NaCl treatment in the Uvhog1 mutant (Fig. 2B; see Supplementary Table S2 online). Similar results were obtained with growth assays on medium with 1 M sorbitol. Treatments with 0.5 M NaCl or 1 M sorbitol resulted in over 99% reduction in colonial growth in the Uvhog1 mutant (Table 2).


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

Zheng D, Wang Y, Han Y, Xu JR, Wang C - Sci Rep (2016)

Growth and conidium germination of the Uvhog1 mutant in the presence of different stresses.(A) The wild-type strain UV-8b, Uvhog1 mutant, and complementary transformant were cultured on YT medium with or without 0.5 M NaCl, 0.07% H2O2, 0.03% SDS (w/v), and 70 μg/ml Congo red. Photographs were taken after incubation at 25 °C for 14 days. (B) Conidia of UV-8b and the Uvhog1 mutant were incubated in YTS with 0.3 M NaCl for 16, 20, or 24 h. Bar = 20 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837404&req=5

f2: Growth and conidium germination of the Uvhog1 mutant in the presence of different stresses.(A) The wild-type strain UV-8b, Uvhog1 mutant, and complementary transformant were cultured on YT medium with or without 0.5 M NaCl, 0.07% H2O2, 0.03% SDS (w/v), and 70 μg/ml Congo red. Photographs were taken after incubation at 25 °C for 14 days. (B) Conidia of UV-8b and the Uvhog1 mutant were incubated in YTS with 0.3 M NaCl for 16, 20, or 24 h. Bar = 20 μm.
Mentions: Because the HOG pathway is well conserved in fungi for responses to hyperosmotic stress1718, we assayed the defects of the Uvhog1 mutant in growth on YT medium with 0.5 M NaCl or 1 M sorbitol. In the presence of 0.5 M NaCl, the Uvhog1 mutant had no obvious growth after incubation for 14 days (Fig. 2A). Under the same conditions, the wild type was reduced in growth rate but still formed compact colonies (Fig. 2A; Table 2). We also assayed the effect of hyperosmotic stress on conidium germination. In the presence of 0.3 M NaCl, most of the wild-type conidia (72.1 ± 1.9%) germinated after incubation in YTS medium for 16 h but only 3.2 ± 1.3% mutant conidia germinated. Even after incubation for 24 h, only 5.0 ± 0.8% conidia produced germ tubes. Moreover, germ tube growth was stunted by NaCl treatment in the Uvhog1 mutant (Fig. 2B; see Supplementary Table S2 online). Similar results were obtained with growth assays on medium with 1 M sorbitol. Treatments with 0.5 M NaCl or 1 M sorbitol resulted in over 99% reduction in colonial growth in the Uvhog1 mutant (Table 2).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.

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.

No MeSH data available.


Related in: MedlinePlus