Characteristics of the Stress-Tolerant Transgenic Wheat Line Overexpressing the AtOPR3 Gene Encoding the Jasmonate Biosynthesis Enzyme 12-Oxophytodienoate Reductase

Abstract

Jasmonates are involved in the regulation of protective mechanisms of plants against unfavorable environments as well as in control of their growth and development. Main data on jasmonate biosynthesis and signals transduction pathways were obtained on model dicotyledonous plant Arabidopsis thaliana. Meanwhile, functions and molecular mode of action of these compounds are still poorly investigated in monocotyledons, including wheat. In the present study, the stress tolerance of transgenic line (Tr-3) and nontransgenic plants of bread wheat cv. Saratovskaya-60 was studied. Transgenic line Tr-3 overexpresses AtOPR3 (12-OXOPHYTODIENOATE REDUCTASE 3) gene from A. thaliana encoding the jasmonate biosynthesis enzyme 12-oxophytodienoate reductase. In spite of the high expression level of AtOPR3, the content of jasmonic acid and its conjugate with isoleucine in intact leaves of the transgenic plants remained unchanged. Furthermore, in the mechanically wounded leaves, the content of jasmonic acid in the transgenic line Tr-3 was even lower than in nontransgenic Saratovskaya-60, while the levels of 12-oxophytodienoic acid and jasmonoil-isoleucine did not differ. In the transgenic plants, the stress-induced expression of the endogenous jasmotate-regulated allene oxide synthase gene was, however, higher than in the nontransgenic control. The transgenic wheat plants were more tolerant to infection by necrotrophic fungus Botrytis cinerea and to osmotic stress caused by polyethylene glycol applied to germinating seeds. The Botrytis-inoculated leaves of the transgenic line Tr-3 manifested higher activity of antioxidant enzyme catalase than inoculated leaves of nontransgenic plants. This fact points to the possible role of catalase in the transgene-associated tolerance to the pathogen. Therefore, the available scarce information concerning the peculiarities of functions of the jasmonate system in wheat plants has been amended with the new data on the role of expression of one of the key genes of jasmonate biosynthesis, namely, 12-OXOPHYTODIENOATE REDUCTASE, in control of defense responses even though the stress-induced level of jasmonic acid is decreased.