Corn Leaf Isoperoxidase Reaction to Mechanical Injury and Infection with Helminthosporium maydis

Abstract

Mechanical injury or infection with Helmintosporium maydis race T or O en proxidase acti in leaves of two corn ibreds which differ in their susceptibility to the fungal race T. Increases in act were found in the soluble fraction extracted from tissues with 20 mm phosphate buffer (pH 6), and in the ionicafUy bound fraction extracted fromn wail debris with 0.6 to 1 M NaCa; the covalently bound wai peroxidase fractin was unaffected. Mechanical injury and infection with either race enhanced the same distinctive cathodic isoforms present in the soluble fraction or in both the soluble and lonicaUy bound fractons.During the firt 20 to 22 hours after ioculation no differences were found in the enzym enhancement in relaton either to the corn line or fungal race. During the second day, the weaker the infection symptom, the greater was the peroxidase encement. infected with the fungus. The same isoperoxidases (IPs) which reacted to infection reacted also to mechanical injury. Such a similarity was also found between mechanically injured and tobacco mosaic virus-infected tobacco leaves (5). The similarities in the reaction to mechanical and viral or fungal injuries were observed not only in the distinctive IPs that increased in activity, but also in their distribution between cell protoplast and walls, thus supporting the assumption that the infection-induced peroxidase enhancement may result from a nonspecific response to injury. Without eliminating the possibility of peroxidase contribution to the plant protection against a parasite, we postulated that the often observed relatively small increases in the enzyme activity in compatible hosts may be a consequence of metabolic disorders rather than the cause of a lower resistance. Vance et al. (23, 24) have recently reported that attempted penetration of Helminthosporwum avenae into leaf discs of a noncompatible host, reed canarygrass, was accompanied by an increase in peroxidase activity, in particular in the walls at the penetration sites, and in wall lignification. Exposure of the inoculated discs to cycloheximide solutions at 10 or 25 itg/ml for 18 hr resulted in inhibition of peroxidase enhancement and lignin formation and in penetration of the fungus into the leaf tissue. The authors have suggested that the resistance mechanism involves an induction of cathodic IPs in the challenged tissue.This report represents a continuation of previous studies on the Funk corn N inbred and its male sterile counterpart and deals with the IP reaction to two H. maydis races, T and 0, differing from each other in the production of the host-specific T toxin. The great compatibility between the Tms inbred and the fungal race T is thought to be due to the susceptibility of the host organelle membranes to the T toxin (2, 19). Both Tms and N inbreds exhibit a low susceptibility to the race 0, nonproducer of the toxin. Special attention has been paid to the effect of cycloheximide on peroxidase enhancement induced by mechanical injury and infection. In view of the implication of et...

Atividade de peroxidase e polifenoloxidase na resistência do feijão à antracnose

“…Cardoso & Garraway (1977) demonstraram que as substâncias provenientes do material castanho da lesão de hipocótilos doentes de feijoeiros inibiam seletivamente isolados não-patogênicos ao feijoeiro. A cultivar AB 136, considerada como altamente resistente ao C. lindemuthianum, seguida pela cultivar Macanudo, apresentaram maior atividade de polifenoloxidase, enquanto a cultivar suscetível Carioca apresentou menor atividade desta enzima (Tabela 1).…”

“…Marriott et al (1978) constataram que aumentos na atividade da peroxidase, associados com ferimentos em vegetais, podem indicar aumento na biossíntese de lignina, que atua como uma barreira à infecção microbiana e também pode promover aumentos na concentração de produtos de oxidação de fenólicos, alterando a concentração de auxinas por causa da presença de AIAoxidase. Birecka & Garraway (1978) também observaram aumentos na atividade da peroxidase em ferimentos ou tecidos infectados, perceptíveis 24 horas após o ferimento e continuando por muitos dias. Alguns trabalhos descrevem que o aumento na atividade da peroxidase é parte da fase geral de ativação do metabolismo, que sintetiza de novo esta enzima (Kanazawa et al, 1965;Fleuriet & Deloire, 1982).…”

Inhibition of Ornithine Decarboxylase and Growth of the Fungus Helminthosporium maydis

“…Repeated freezing and thawing, sonication, and maceration with glass beads was applied during extraction at 0 to 4°C. The enzymes were assayed as described previously (3,4) in the presence of 1 mM MgCl2 (14). The enzyme inhibitors DFMO (DL-a-difluoromethylornithine hydrochloride monohydrate, MDL 71782) and DFMA (DL-a-difluoromethylarginine hydrochloride monohydrate, MDL 71897) were synthesized at Merrell Dow Research Institute.…”

“…Repeated freezing and thawing, sonication, and maceration with glass beads was applied during extraction at 0 to 4°C. The enzymes were assayed as described previously (3,4) …”

Pb-Stress Induced Oxidative Stress Caused Alterations in Antioxidant Efficacy in Two Groundnut (<i>Arachis hypogaea</i> L.) Cultivars

“…SOD isoforms were visualized following the method described by Beauchamp and Fridovich [43]. Activity of GPX isoforms was visualized on 7.5% gel according to staining procedure of Birecka [44]. In-gel APX activity staining was performed according to Lee and Lee [45].…”