RESUMOMuitas plantas passam por mudanças bioquímicas significativas em resposta ao ataque de estressores bióticos, como patógenos ou insetos herbívoros. Ambos estressores bióticos quando atacam as plantas fazem com que estas respondam de forma rápida com uma "explosão oxidativa", que constituem na produção de espécies reativas de oxigênio (ERO), principalmente ânion superóxido (O 2•-) e peróxido de hidrogênio (H 2 O 2 ). O acúmulo destas substâncias nas células vegetais pode ser tóxico para ambos. Estas EROs acionam moléculas para a indução de genes de defesa e a polimerização de proteínas que compõe a parede celular, além de estimular a produção de enzimas antioxidativas ou de limpeza. Existe uma variedade destas enzimas que irão decompor as espécies reativas de oxigênio. Como por exemplo, temos superóxido dismutase (SOD), peroxidase (POX), catalase (CAT), polifenol oxidase (PPO), entre outras. Nesta revisão será abordado como a herbivoria e a patogenicidade desencadeiam uma explosão oxidativa ativando o sistema de defesa da planta com a ação das enzimas antioxidativas. PALAVRAS-CHAVE: catalase, peroxidase, estresse biótico, inseto, fungo. THE ROLE OF ANTIOXIDANT ENZYMES IN PLANT DEFENSE AGAINST HERBIVOROUS INSECTS AND PHYTOPATHOGENSABSTRACT Many plants suffer significant biochemical changes in response the attack of biotic stressors, such as phytopathogens or herbivorous insects. When any of these biotic stressors attack plants, this causes quick responses via an "oxidative burst", which constitutes the production of reactive oxygen species (ROS), particularly superoxide anion (O 2•-) and hydrogen peroxide (H 2 O 2 ). The accumulation of these substances in vegetal cells can be toxic to both the biotic stressors and plants. These ROS will trigger molecules for the induction of defense genes and polymerization of proteins that makes up the cell walls, as well as stimulate the production of antioxidant enzymes or scavenging. There are a variety of these enzymes that will decompose the reactive oxygen species; the superoxide dismutase (SOD), peroxidase (POX), catalase (CAT) and polyphenol oxidase (PPO) are some examples. This review will describe how herbivory and pathogenic triggers cause an oxidative burst stimulating the defense system of the plants with the actions of antioxidant enzymes.
This study aimed to observe the response of 32 rice accessions to attack of sugarcane borer (Diatraea saccharalis Fabr., 1794). Twenty larvae were placed on the leaf sheaths of rice plants. At 30 days after infestation, the rice plants were cut at ground level and taken to the laboratory to analyse the signs of borer attack, external and internal diameter of the stem and weight of surviving larvae. The results of the morphological traits of the rice plant, response of the plant to insect attack and development of the sugarcane borer larvae indicated a genotypic variation. The accessions that most favored larval survivals were IRAT 124 and MEARIN. Larvae with highest weight (0.0643 g) were found in IAPAR L 99-98 and the largest internal diameters of the rice stem (5.65 mm) were found in LAC 12. These accessions (IRAT 124, MEARIN, IAPAR L 99-98 and LAC 12) remained morphologically grouped with IAC 47, cultivar susceptible to sugarcane borer. The most tolerant materials based on the ability to produce new tillers after larval infestation were BR IRGA 417 and MTU 15. The results of this study indicate that all the morphological traits were able to separate the accessions of rice into different groups in relation to resistance to the sugarcane borer D. saccharalis. These materials can be used as donor sources in pre-breeding for genetic resistance to sugarcane borers.
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