title: Tomato QM-like protein protects Saccharomyces cerevisiae cells against oxidative stress by regulating intracellular proline levels.
abstract: Exogenous proline can protect cells of Saccharomyces cerevisiae from oxidative stress. We altered intracellular proline levels by overexpressing the proline dehydrogenase gene (PUT1) of S. cerevisiae. Put1p performs the first enzymatic step of proline degradation in S. cerevisiae. Overexpression of Put1p results in low proline levels and hypersensitivity to oxidants, such as hydrogen peroxide and paraquat. A put1-disrupted yeast mutant deficient in Put1p activity has increased protection from oxidative stress and increased proline levels. Following a conditional life/death screen in yeast, we identified a tomato (Lycopersicon esculentum) gene encoding a QM-like protein (tQM) and found that stable expression of tQM in the Put1p-overexpressing strain conferred protection against oxidative damage from H2O2, paraquat, and heat. This protection was correlated with reactive oxygen species (ROS) reduction and increased proline accumulation. A yeast two-hybrid system assay was used to show that tQM physically interacts with Put1p in yeast, suggesting that tQM is directly involved in modulating proline levels. tQM also can rescue yeast from the lethality mediated by the mammalian proapoptotic protein Bax, through the inhibition of ROS generation. Our results suggest that tQM is a component of various stress response pathways and may function in proline-mediated stress tolerance in plants.
authors.affiliation: Institute for Plant Genomics and Biotechnology, Department of Plant Pathology and Microbiology, Texas A&M University, 2123 TAMU, College Station, TX 77843, USA.
authors.forename: Changbin
authors.initials: C
authors.lastname: Chen
authors.forename: Srimevan
authors.initials: S
authors.lastname: Wanduragala
authors.forename: Donald F
authors.initials: DF
authors.lastname: Becker
authors.forename: Martin B
authors.initials: MB
authors.lastname: Dickman
mesh_terms: D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology*; D018551:Solanum lycopersicum / Q000502:physiology*; D018384:Oxidative Stress / Q000187:drug effects*; D010940:Plant Proteins / Q000494:pharmacology*; D011392:Proline / Q000378:metabolism*; D011394:Proline Oxidase / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000502:physiology*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D010940:Plant Proteins; D011392:Proline; D011394:Proline Oxidase