Functional analysis of polyphenol oxidases by antisense/Sense Technology

โครงการหนึ่งอาจารย์หนึ่งผลงาน ประจำปี 254

Functional Analysis of Polyphenol Oxidases by Antisense/Sense Technology

Polyphenol oxidases (PPOs) catalyze the oxidation of phenolics to quinones, the secondary reactions of which lead to oxidative browning and postharvest losses of many fruits and vegetables. PPOs are ubiquitous in angiosperms, are inducible by both biotic and abiotic stresses, and have been implicated in several physiological processes including plant defense against pathogens and insects, the Mehler reaction, photoreduction of molecular oxygen by PSI, regulation of plastidic oxygen levels, aurone biosynthesis and the phenylpropanoid pathway. Here we review experiments in which the roles of PPO in disease and insect resistance as well as in the Mehler reaction were investigated using transgenic tomato (Lycopersicon esculentum) plants with modified PPO expression levels (suppressed PPO and overexpressing PPO). These transgenic plants showed normal growth, development and reproduction under laboratory, growth chamber and greenhouse conditions. Antisense PPO expression dramatically increased susceptibility while PPO overexpression increased resistance of tomato plants to Pseudomonas syringae. Similarly, PPO-overexpressing transgenic plants showed an increase in resistance to various insects, including common cutworm (Spodoptera litura (F.)), cotton bollworm (Helicoverpa armigera (Hübner)) and beet army worm (Spodoptera exigua (Hübner)), whereas larvae feeding on plants with suppressed PPO activity had higher larval growth rates and consumed more foliage. Similar increases in weight gain, foliage consumption, and survival were also observed with Colorado potato beetles (Leptinotarsa decemlineata (Say)) feeding on antisense PPO transgenic tomatoes. The putative defensive mechanisms conferred by PPO and its interaction with other defense proteins are discussed. In addition, transgenic plants with suppressed PPO exhibited more favorable water relations and decreased photoinhibition compared to nontransformed controls and transgenic plants overexpressing PPO, suggesting that PPO may have a role in the development of plant water stress and potential for photoinhibition and photooxidative damage that may be unrelated to any effects on the Mehler reaction. These results substantiate the defensive role of PPO and suggest that manipulation of PPO activity in specific tissues has the potential to provide broad-spectrum resistance simultaneously to both disease and insect pests, however, effects of PPO on postharvest quality as well as water stress physiology should also be considered. In addition to the functional analysis of tomato PPO, the application of antisense/sense technology to decipher the functions of PPO in other plant species as well as for commercial uses are discussed

PPO expression and accumulation during pollen germination and pollen tube growth

ผลงานวิชาการคณาจารย์มหาวิทยาลัยเทคโนโลยีสุรนาร

Functional analysis of polyphenol oxidases by antisense/sense technology

Polyphenol oxidases (PPOs) catalyze the oxidation of phenolics to quinones, the secondary reactions of which lead to oxidative browning and postharvest losses of many fruits and vegetables. PPOs are ubiquitous in angiosperms, are inducible by both biotic and abiotic stresses, and have been implicated in several physiological processes including plant defense against pathogens and insects, the Mehler reaction, photoreduction of molecular oxygen by PSI, regulation of plastidic oxygen levels, aurone biosynthesis and the phenylpropanoid pathway. Here we review experiments in which the roles of PPO in disease and insect resistance as well as in the Mehler reaction were investigated using transgenic tomato (Lycopersicon esculentum) plants with modified PPO expression levels (suppressed PPO and overexpressing PPO). These transgenic plants showed normal growth, development and reproduction under laboratory, growth chamber and greenhouse conditions. Antisense PPO expression dramatically increased susceptibility while PPO overexpression increased resistance of tomato plants to Pseudomonas syringae. Similarly, PPO-overexpressing transgenic plants showed an increase in resistance to various insects, including common cutworm (Spodoptera litura (F.)), cotton bollworm (Helicoverpa armigera (Hübner)) and beet army worm (Spodoptera exigua (Hübner)), whereas larvae feeding on plants with suppressed PPO activity had higher larval growth rates and consumed more foliage. Similar increases in weight gain, foliage consumption, and survival were also observed with Colorado potato beetles (Leptinotarsa decemlineata (Say)) feeding on antisense PPO transgenic tomatoes. The putative defensive mechanisms conferred by PPO and its interaction with other defense proteins are discussed. In addition, transgenic plants with suppressed PPO exhibited more favorable water relations and decreased photoinhibition compared to nontransformed controls and transgenic plants overexpressing PPO, suggesting that PPO may have a role in the development of plant water stress and potential for photoinhibition and photooxidative damage that may be unrelated to any effects on the Mehler reaction. These results substantiate the defensive role of PPO and suggest that manipulation of PPO activity in specific tissues has the potential to provide broad-spectrum resistance simultaneously to both disease and insect pests, however, effects of PPO on postharvest quality as well as water stress physiology should also be considered. In addition to the functional analysis of tomato PPO, the application of antisense/sense technology to decipher the functions of PPO in other plant species as well as for commercial uses are discussed. © 2007 by MDPI

Overexpression of tomato polyphenol oxidase increases resistance to common cutworm

Polyphenol oxidases (PPOs), which catalyze the oxidation of phenolics to quinones, have been reported to confer resistance to Pseudomonas syringae and are thought to be involved in insect resistance. To assess the impact of PPO expression on resistance to the common cutworm (Spodoptera litura (F.)) (Lepidoptera: Noctuidae), we used transgenic tomato (Lycopersicon esculentum Mill.) plants constitutively expressing sense- and antisense-oriented potato PPO genes. Transgenic plants expressing a sense PPO construct (overexpressing PPO [OP] plants) exhibited 2.0-5.7-fold higher PPO activity levels, whereas antisense PPO transgenic plants (suppressed PPO [SP] plants) exhibited 1.5-7.3-fold lower PPO activity levels than nontransformed controls. The PPO-overexpressing transgenic plants clearly showed an increase in resistance; simple growth rates of common cutworms on OP plants were up to 2.5 and 3.3 times lower than on controls and SP leaves, respectively, and larvae consumed less foliage. In addition, increased PPO activity led to higher larval mortality. The efficiency of conversion of ingested food and efficiency of conversion of digested food of third instars were found to be significantly different among tomato genotypes with differing PPO activity levels, suggesting that PPO activity rendered foliage less nutritious. Moreover, when leaflets at nodes 4 and 8 of SP, NT and OP plants were detached and fed to common cutworm larvae, their PPO activity levels were induced 1.6-2.2-fold. These results suggest a critical role for PPO-mediated phenolic oxidation in resistance to this insect. Manipulation of PPO activity could provide resistance simultaneously to both disease and insect pests, and therefore might be used as a component of effective integrated pest management. © 2008 Elsevier Ireland Ltd. All rights reserved