Wang P, Nuss D L
Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110, USA.
Proc Natl Acad Sci U S A. 1995 Dec 5;92(25):11529-33. doi: 10.1073/pnas.92.25.11529.
Extracellular cellulase activity is readily induced when the chestnut blight fungus Cryphonectria parasitica is grown on cellulose substrate as the sole carbon source. However, an isogenic C. parasitica strain rendered hypovirulent due to hypovirus infection failed to secrete detectable cellulase activity when grown under parallel conditions. Efforts to identify C. parasitica cellulase-encoding genes resulted in the cloning of a cellobiohydrolase (exoglucanase, EC 3.2.1.91) gene designated chb-1. Northern blot analysis revealed an increase in cbh-1 transcript accumulation in a virus-free virulent C. parasitica strain concomitant with the induction of extracellular cellulase activity. In contrast, induction of cbh-1 transcript accumulation was suppressed in an isogenic hypovirus-infected strain. Significantly, virus-free C. parasitica strains rendered hypovirulent by transgenic cosuppression of a GTP-binding protein alpha subunit were also found to be deficient in the induction of cbh-1 transcript accumulation.
当栗疫病菌寄生隐孢壳菌（Cryphonectria parasitica）在以纤维素底物作为唯一碳源的培养基上生长时，胞外纤维素酶活性很容易被诱导。然而，由于感染低毒病毒而导致毒力减弱的同基因寄生隐孢壳菌菌株，在平行条件下生长时未能分泌可检测到的纤维素酶活性。对寄生隐孢壳菌纤维素酶编码基因的鉴定工作，导致了一个被命名为chb-1的纤维二糖水解酶（外切葡聚糖酶，EC 3.2.1.91）基因的克隆。Northern印迹分析显示，在无病毒的强毒寄生隐孢壳菌菌株中，cbh-1转录本积累增加，同时伴随着胞外纤维素酶活性的诱导。相比之下，在同基因的低毒病毒感染菌株中，cbh-1转录本积累的诱导受到抑制。值得注意的是，通过对GTP结合蛋白α亚基进行转基因共抑制而导致毒力减弱且无病毒的寄生隐孢壳菌菌株，也被发现缺乏cbh-1转录本积累的诱导。
