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Ability of L-proline to suppress ROS-induced apoptotic-like cell death in Colletotrichum trifolii

Seminar Abstract

The small GTP-binding protein Ras is known to play a critical role in regulating cellular signal transduction processes leading to cell growth, differentiation and survival. Previously, Gina et al. found that a dominant active form of Ras, when expressed in Colletotrichum trifolii, yielded a nutrient-dependent response. Under conditions of nutrient deprivation (minimal media), the activated DARas mutant induced aberrant hyphal proliferation, defects in polarized growth and significantly, reduced differentiation such as conidiation and appressorium formation. More interestingly, Memmot et al. found that L-proline, when added to minimal media with a concentration of 1.6mM, is sufficient to fully restore the wild type phenotype including restoration of normal hyphal morphology and conidiation. However, the mechanisms by which proline protect Ct-RasVal2 mutant from abnormal growth and development are completely unclear. Recently, we observed that the dominant active Ras mutant (DARas) generates a high concentration of reactive oxygen species (ROS) in minimal media and L-proline can suppress the ROS production. Moreover, we found that high level of ROS produced in DARas mutant mediates an apoptotic-like cell death and L-proline functions to inhibit this action. Our data suggest that L-proline may act as an antioxidant to suppress the ROS-induced apoptosis in DARas mutant when grown in nutrient-limiting condition.

Research Interest

My research interest is focusing on the characterization of signal transduction pathways responsible for the regulation of hyphal growth and development in two different filamentous fungi, Colletotrichum trifolii and Sclerotinia sclerotiorum. Some important signaling-related genes have been characterized in these two fungi, including TB3, a serine/threonine protein kinase, which is required for hyphal branching and elongation; Ras and Rac, small GTP-binding proteins required for proper hyphal growth and development; and MAP kinase, which is necessary for sclerotial development in S. sclerotiorum.

Background:

B.S. Shanghai Fudan University, China (1995)
M.S. Chinese Academy of Sciences, China (1998)
Ph.D. Martin Dickman' lab. Plant Pathology Dept. UNL. (1998-)