O Papel Das Enzimas Antioxidantes Na Defesa Das Plantas Contra Insetos Herbívoros E Fitopatógenos

Abstract

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.

Resistance inducers and biochemical mechanisms in the control of anthracnose in cowpea

“…When subjected to abiotic or biotic stress, the plants rapidly produced reactive oxygen species such as singlet oxygen ( 1 O 2 ), anion superoxide (O 2 -), and, especially, hydrogen peroxide (H 2 O 2 ) and the hydroxyl group (OH -). The accumulation of these substances in plant cells has a toxic effect on both plants and stressor agents (Nascimento and Barrigossi, 2014). To protect against the side effects of these reactive oxygen species, plant cells initiate a defense system with the production of enzymes and other molecules, such as carotenoids, ascorbic acid, vitamin E, flavonoids, proline, and glutathione, together with the induction of plant defense genes and the polymerization of proteins that compose the cell wall (Davar et al, 2013).…”

“…Understanding plant defense mechanisms enables the development of plant varieties that are more resistant to several types of phytopathogens and pests (Nascimento and Barrigossi, 2014). Treating plants with abiotic and biotic inducers of systemic resistance may increase systemic resistance against pathogens in plants.…”

Indutores de resistência abióticos no controle da fusariose do abacaxi

“…reticulação de componentes da parede celular e senescência (Nascimento & Barrigossi, 2014). Sua atividade na planta diminui em relação ao tempo decorrido após a exposição inicial a um agente indutor (Macagnan et al, 2008).…”

The effect of drought conditions on sweet orange (Citrus sinensis) plants infected with citrus tristeza virus (CTV)

“…Furthermore, under stress conditions (whether abiotic or biotic), an oxidative burst can occur in the stressed plant very rapidly, consisting of the accumulation of reactive oxygen species (ROS), mainly superoxide anion (O 2 − ), hydrogen peroxide (H 2 O 2 ) and hydroxyl radical (OH − ) ions (Hegedus et al Section Editor: F. Murilo Zerbini 2001;Hu et al 2009). To protect themselves from this burst of oxidative radicals, organelles including chloroplasts, mitochondria and peroxisomes use an antioxidant defense system, which includes the production of enzymes that will eliminate ROS, such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) (Nascimento and Barrigossi 2014).…”