Expression of a serine protease gene prC is up-regulated by oxidative stress in the fungus Clonostachys rosea: implications for fungal survival.
BACKGROUND
Soil fungi face a variety of environmental stresses such as UV light, high temperature, and heavy metals. Adaptation of gene expression through transcriptional regulation is a key mechanism in fungal response to environmental stress. In Saccharomyces cerevisiae, the transcription factors Msn2/4 induce stress-mediated gene expression by binding to the stress response element. Previous studies have demonstrated that the expression of extracellular proteases is up-regulated in response to heat shock in fungi. However, the physiological significance of regulation of these extracellular proteases by heat shock remains unclear. The nematophagous fungus Clonostachys rosea can secret an extracellular serine protease PrC during the infection of nematodes. Since the promoter of prC has three copies of the stress response element, we investigated the effect of environmental stress on the expression of prC.


RESULTS
Our results demonstrated that the expression of prC was up-regulated by oxidants (H(2)O(2) or menadione) and heat shock, most likely through the stress response element. After oxidant treatment or heat shock, the germination of conidia in the wild type strain was significantly higher than that in the prC mutant strain in the presence of nematode cuticle. Interestingly, the addition of nematode cuticle significantly attenuated the production of reactive oxygen species (ROS) induced by oxidants and heat shock in the wild type strain, but not in prC mutant strain. Moreover, low molecule weight (<3 kD) degradation products of nematode cuticle suppressed the inhibitory effect of conidial germination induced by oxidants and heat shock.


CONCLUSIONS
These results indicate that PrC plays a protective role in oxidative stress in C. rosea. PrC degrades the nematode cuticle to produce degradation products, which in turn offer a protective effect against oxidative stress by scavenging ROS. Our study reveals a novel strategy for fungi to adapt to environmental stress.
Laboratory for Conservation and Utilization of Bio-Resources & Key Laboratory for Microbial Resources of the Ministry of Education, Yunnan University, Kunming, Yunnan, China.
Cheng-Gang
CG
Zou
Yong-Fang
YF
Xu
Wen-Jing
WJ
Liu
Wei
W
Zhou
Nan
N
Tao
Hui-Hui
HH
Tu
Xiao-Wei
XW
Huang
Jin-Kui
JK
Yang
Ke-Qin
KQ
Zhang
D001203:Ascomycota / Q000201:enzymology / Q000235:genetics*; D018384:Oxidative Stress; D011401:Promoter Regions, Genetic; D017382:Reactive Oxygen Species / Q000378:metabolism; D057057:Serine Proteases / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
D017382:Reactive Oxygen Species; D057057:Serine Proteases