Polyphenoloxidase activity in soybean hypocotyls at sites inoculated with Phytophthora megasperma f. sp. glycinea (original) (raw)
Related papers
Canadian Journal of Botany, 1988
Phenylalanine ammonia-lyase activity increased rapidly beginning 2 h after inoculation with Phytophthora megasperma (Drechs.) f.sp. glycinea (Hildeb.) Kuan & Erwin race 1 in unwounded hypocotyls of soybean cv. Harosoy 63 (resistant) but did not change significantly in cv. Harosoy (susceptible). Small increases in phenylalanine ammonia-lyase activity also were caused by wounding. Activity increased more slowly in hypocotyls (cv. Harosoy 63) wounded just before inoculation than in intact inoculated hypocotyls, but most activity developed in hypocotyls wounded 12 h before inoculation. There were comparable effects of wounding on symptom development. Trifoliolate leaves of 14-day-old cv. Harosoy 63 plants are resistant, but trifoliolate leaves of 12-day-old cv. Harosoy 63 plants and of 14-day-old cv. Harosoy plants are susceptible to race 1. Increases in phenylalanine ammonia-lyase activity following inoculation were demonstrated only in 14-day-old Harosoy 63 plants but not until 24–36 ...
The hypersensitive response is associated with host and nonhost resistance to Phytophthora infestans
Planta, 2000
The interaction between Phytophthora infestans (Mont.) de Bary and Solanum was examined cytologically using a diverse set of wild Solanum species and potato (S. tuberosum L.) cultivars with various levels of resistance to late blight. In wild Solanum species, in potato cultivars carrying known resistance (R) genes and in nonhosts the major defense reaction appeared to be the hypersensitive response (HR). In fully resistant Solanum species and nonhosts, the HR was fast and occurred within 22 h. This resulted in the death of one to three cells. In partially resistant clones, the HR was induced between 16 and 46 h, and resulted in HR lesions consisting of five or more dead cells, from which hyphae were occasionally able to escape to establish a biotrophic interaction. These results demonstrate the quantitative nature of the resistance to P. infestans. The effectiveness of the HR in restricting growth of the pathogen differed considerably between clones and correlated with resistance levels. Other responses associated with the defense reaction were deposition of callose and extracellular globules containing phenolic compounds. These globules were deposited near cells showing the HR, and may function in cell wall strengthening.
Physiological and Molecular Plant Pathology, 2002
We studied the eect of temporary hypoxia on responses associated with disease resistance in cell suspensions of tobacco and soybean challenged with zoospores of compatible and incompatible races of Phytophthora nicotianae and Phytophthora sojae, respectively. Under normal atmospheric conditions both hosts respond to incompatible challenge with a burst of superoxide (O 2 À ) release beginning 6 h after inoculation, followed within 2 h by the onset of cell death. NBT staining reveals that O 2 À is released around the point of contact between the pathogen and cell in both hosts. Hypoxia, imposed by incubating challenged cells under an atmosphere of nitrogen between 4 and 9 h after inoculation, abolishes the O 2 À burst and cell death in both tobacco and soybean cells. Under these conditions normally incompatible pathogen races infect and colonize host cells, indicating a failure of resistance expression. Compatible interactions, and the viability of uninoculated cells of tobacco and soybean, are not aected by temporary hypoxia. These results strongly implicate a requirement for oxygen, O 2 À release and hypersensitive cell death in the resistance of tobacco and soybean to incompatible pathogen races. *
Nematology, 2007
The role of the enzyme polyphenoloxidase (PPO) in the response of two soybean varieties, Hartwig (resistant) and Cristalina (susceptible), to Meloidogyne javanica was studied in plants where root systems were exposed to the known PPO inducer, methyljasmonate. Chlorogenic acid was the best substrate for root PPO. Treatment of both varieties with 100 and 400 μM methyljasmonate solutions induced a similar increase in enzyme activity 72 h after treatment. Inoculation of roots with second-stage juveniles (J2) induced PPO increase in cv. Cristalina but not in cv. Hartwig. Moreover, combined treatment of methyljasmonate and J2 inoculation enhanced PPO activity in both varieties. Two PPO cDNAs were isolated from the roots of the resistant variety 48 h after J2 inoculation, and Southern blot experiments in both varieties, using GmPPOJH1 and GmPPOJH2 cDNAs as probes, indicated that PPOs are represented by a multigene family in soybean. RT-PCR assays showed more GmPPOJH1 transcripts in plants ...
Effect of a benzothiadiazole on inducing resistance of soybean to Phytophthora sojae
Protoplasma, 2013
Effects of benzothidiazole (BTH), an inducer of resistance, were examined in a compatible interaction of soybean seedlings and Phytophthora sojae using electron microscopy and quantitative real-time polymerase chain reaction (qRT-PCR) techniques. Seedlings were sprayed with BTH 2 days before inoculation of hypocotyls with zoospore suspension of P. sojae. In hypocotyls treated with BTH, the infection process of P. sojae was significantly delayed, and also the structures of hyphae and haustorium-like bodies were remarkably altered. These changes included increased vacuolation, plasmolysis, degeneration of cytoplasm, and collapse of hyphae and haustorium-like bodies. Large morphological differences were detected in P. sojae-infected hypocotyl tissue treated with BTH compared with infected but non-treated control tissue. Very thick layers of wall appositions were formed in the host cells contacting with hyphae, whereas such structures were never observed in only P. sojae-infected control hypocotyls. In addition, five pathogenesis-related (PR)genes were selected to detect their transcription changes using qRT-PCR. Expression of PR-1, PR-3a, PR-3b, PR-9, and PR-10 genes were induced in BTH-treated and P. sojae-inoculated tissue at different times and levels. The up-regulated expression of these genes as well as the morphological defense structures may contribute to disease resistance in soybean hypocotyls to P. sojae.
Chemical-induced resistance against brown stem rot in soybean: the effect of benzothiadiazole
2008
In the present work, the biochemical basis of tolerance in soybean to stem rot via its priming with benzothiadiazole (BTH) was investigated. To evaluate the potentiation of BTH in this respect, differences in the elements associated with the induction of defenses were traced before and after subjecting soybean to biotic stress induced by its inoculation with Phialophora gregata. BTH priming of non-inoculated soybeans was observed to increase percentage of seed germination, fresh and dry weights of shoots and roots and photosynthetic pigments. Marked differences in the phenolics, lignin, flavonoids and the enzymes involved in the regulation of their metabolism namely: phenylalanine ammonia-lyase (PAL), Peroxidase POX and polyphenol oxidase (PPO) were recorded. Leaf tissues of soybeans which were primed with BTH responded differently to pathogen inoculation with Phialophora gregata, compared with both the control and BTH-primed and non-challenged ones. Appreciable increase in the activity level of PAL, POX and PPO was observed in response to challenging of BTH-primed soybean, particularly on applying it as both seed soaking followed by foliar spraying. On the other hand, catalase activity subjected to marked increase in non-challenged, BTH-treated soybeans meanwhile it was obviously decreased upon pathogen inoculation of BTH-treated plants. Appreciable increase in the different forms of phenolics (free, conjugated, cell wall-bound phenolics and total soluble phenols) was recorded in response to BTH-priming and challenging. Moreover, the same treatments induced obvious increase in the flavonoid content of soybean leaves. Thus, a four-fold increase in leuteolin content was observed in treated tissues, compared with the control. Also, the quercetin and genistein content subjected to marked increase in response to BTH and challenging with Phialophora gregata. The bioassay for antifungal activity of phenolic compounds obtained from BTH-primed and challenged soybeans revealed its high toxicity to fungal spore germination. The marvelous changes induced in protein pattern in response to priming soybean with BTH and its challenging with its pathogen, refer to that BTH act at the molecular level and that it induced change at the transcriptional and translational levels.
Journal of Plant Physiology, 1991
Seedling roots of different varieties of soybean have been infected with various strains of the soybean pathogen Phytophthora megasperma f. sp. glycinea (Pmg), resulting in compatible and incompatible interactions. Infected roots displayed an increase in ethylene biosynthesis in all cases. Upon infection of the soybean cultivar Harosoy with Pmg race 1 or 3 or of cultivar Harosoy 63 with Pmg race 3, resulting in compatible interactions, the rate of ethylene biosynthesis started to increase ca. 6 h after infection and reached ca. 10-lS-fold induction 11-12 h after inoculation. In the incompatible interaction of the soybean cultivars Maple Arrow or Harosoy 63 with Pmg race 1, however, ethylene production was stimulated 5-10-fold as early as 3 h after infection and reached its maximum, a ca. 50-fold induction, already 6 h after inoculation. Soybean roots treated with elicitor preparations from Phytophthora megasperma cell walls showed no increase in ethylene biosynthesis although they accumulated glyceollin, the main phytoalexin of soybean, to a similar degree as infected roots. Addition of l-aminocyclopropane-l-carboxylic acid to soybean roots increased ethylene production without affecting glyceollin accumulation. We conclude that in soybean roots, an early burst of ethylene biosynthesis is a characteristic symptom of the incompatible reaction that cannot be mimicked by treatment with fungal elicitors.
Physiological and Molecular Plant Pathology
The expression of resistance and susceptibility to inoculation with zoospores of Phytophthora megasperma f. sp.g{ycinea race I was determined ill roots, hypocotyls, and cotyledons of etiolated and green seedlings and in leaves of soybean cvs Harosoy (rpsl) and Harosoy 6~(Rpsl)' Gene-specific resistance was demonstrated in all organs tested, except for cotyledons of etiolated seedlings. In each case higher concentrations of the glyceollins accumulated in resistant than in susceptible reactions; the differential being greatest in hypocotyls and smallest in roots. The relative proportions of glyceollins I, II and III varied with the organ, exposure of'the seedlings to light, the interaction type and the incubation period. Glyceollin I was relatively the most abundant isomer in roots and to a lesser extent in hypocotyls. Glyceollin III was relatively the most abundant isomerin leaves. Major differences in accumulation rates were observed in time-course experiments and, after reaching a maximum, all three isomers decreased in leaves and glyceollin I decreased in hypocotyls, suggesting that concentrations and hence isomeric proportions were finely controlled by rates of biosynthesis and metabolism.
Physiological and Molecular Plant Pathology
In unwounded soybean hypocotyls, pulse labelled with [ 14 C]phenylalanine and inoculated with Phytophthora megasperma Esp. glycinea, rates of [ 14 C]-incorporation and glyceollin I accumulation were higher in resistant than in susceptible responses throughout the time-course of the experiment. This distinction was masked in hypocotyls that were wounded and inoculated. In such hypocotyls, high rates of [ 14C]-incorporation developed that were similar for the first 11 h in resistant and susceptible responses, although much more glyceollin I accumulated in the former. High rates of [ 14 C]-incorporation also developed in uninoculated wounded hypocotyls but only small amounts of glyceollin I of high specific radioactivity were detected. Estimates of phenylalanine ammonia-lyase activity indicated that the metabolic flux through phenylalanine was limited in wounded controls but potentially very high in resistant responses. Differences in rates of[14C]-incorporation and in specific radioactivity of accumulated glyceollin I presumably indicate differences in the relative contributions of mobile internal pools and externally applied phenylalanine, in addition to rates of biosynthesis. Rapid decline in [ 14 C]-glyceollin I was demonstrated in wounded controls in pulsechase experiments with phenylalanine as chase, but not in inoculated hypocotyls, due to continued [ 14 C1-incorporation during the chase period. Rapid metabolism was demonstrated in all interactions and in wounds when cinnamic acid was used as the chase, but there was no evidence that differences in glyceollin I accumulation were due to differential rates of metabolism. Additional evidence for metabolic activity was provided by pulse feeding with [ 14 C] glyceollin I. It is concluded that the stimulus of wounding or infection induces a metabolic pathway in which glyceollin I is not an end product. The accumulation of higher levels of glyceollin I in resistant than in susceptible responses appears to be due to earlier initiation and subsequently higher rates of biosynthesis in the former .