Language：English   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Participation form：Joint(The vice charge)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Mycoscience  

© 2019 The Mycological Society of Japan A mitogen-activated protein kinase (MAPK) signaling pathway regulates specialized cellular responses to external stimuli. In Bipolaris maydis, a Chk1 MAPK orthologous to Fus3/Kss1 MAPKs of Saccharomyces cerevisiae is known to regulate various developmental processes, including the formation of appressoria. However, upstream factors that regulate the Chk1 cascade have not been well clarified. In this study, we identified and characterized the BmSte50 gene, an ortholog of the yeast Ste50 in B. maydis. Our yeast two-hybrid assay indicated that BmSte50 interacts with a MAPK kinase kinase BmSte11, a component of the Chk1 cascade. ΔBmSte50 strains exhibited a loss of pathogenicity due to a lack of appressorial formation. The mutants also showed a reduction in melanization, conidial production, and aerial-mycelial and sexual development. Such phenotypes of the mutants were consistent with those of the Chk1 cascade gene mutants previously reported. In addition, ΔBmSte50 strains indicated lower conidial germination efficiency than the wild type. Notably, a significant number of ΔBmSte50 conidia could be germinated, while the Chk1 cascade gene mutants were reported to lack conidial germination ability. Our results suggested that BmSte50 may act as an adaptor protein for the Chk1 cascade and is involved in the regulation of various cellular processes.

DOI： 10.1016/j.myc.2019.10.003

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Current Genetics  

© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. PAK (p21-activated protein kinases)-like kinases are master regulators of development and morphogenesis, which were conserved among eukaryotes, including fungi. In budding yeast, two types of PAK-like kinases, Ste20 and Cla4 have distinct but shared roles in the regulation of pseudohyphal development, budding and mating. In this study, to examine the broad functions of PAK-like kinases in growth, pathogenicity and asexual/sexual reproduction in filamentous fungi, we identified and characterized two PAK-like kinases, Ste20 and Cla4 in Bipolaris maydis. A single mutant of both Ste20 and Cla4 gene was viable, while the double mutant was not available, possibly because of lethality. In growth, conidiation, and pathogenicity, Δste20 strains showed phenotypes similar to those of the wild-type, while Δcla4 strains showed severely defected phenotypes. In this study, we also clarified that Ste20 is partially involved in pseudothecium development but is dispensable for maternity, while Cla4 is essential for maternal pseudothecium development and also involve in ascospore development in paternal pseudothecium. Fluorescent microscopy visualized the disorder in cell polarity at the hyphal tip in Δcla4. These results suggested that not Ste20 but Cla4 is a master regulator of growth, pathogenicity and asexual/sexual development in B. maydis. In addition, we successfully visualized alternation of branching pattern and distribution of Spitzenkörper at the hyphal tip in Δcla4 strains.

DOI： 10.1007/s00294-019-00977-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Soil Science and Plant Nutrition  

© 2019, © 2019 Japanese Society of Soil Science and Plant Nutrition. The response of soil organic matter (SOM) to global warming is a crucial subject. However, the temperature sensitivity of SOM turnover remains largely uncertain. Changes in the mineralization of native SOM, i.e., priming effect (PE) may strongly affect the temperature sensitivity of SOM turnover in the presence of global warming. We investigated the direction and magnitude of the PE in a Japanese volcanic ash soil at different temperatures (15°C, 25°C, and 35°C) using a natural 13C tracer (C4-plant, maize leaf) in a short-term (25 days) incubation study. In addition, we evaluated the temperature sensitivity expressed as Q10 value with and without the addition of maize to the soil and their relations to PE. We found that positive PE occurred at each temperature condition and tended to increase with decreased temperature, and these PE results were consistent with the microbial biomass at the end of the incubation period. CO2 emission from control soil (without maize) increased with increasing temperature (Q10 = 2.6), but CO2 emission from the soil with added maize did not significantly change with increasing temperature (Q10 = 1.0). This was caused by the suppression of CO2 emission from the soil with increasing temperature (Q10 = 0.9). On the other hand, soil-originated CO2 emission clearly increased with increasing temperature (Q10 = 3.4) when Q10 values were calculated on the assumption that the temperature and substrate supply increase at the same time (from 25°C). These results suggest that not only the temperature increase but also the labile carbon supply may be important for the temperature sensitivity of Japanese volcanic ash soil.

DOI： 10.1080/00380768.2019.1665969

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