Crop productivity is greatly influenced by various environmental stresses, of which insect herbivory-induced biotic stress assumes much significance. As a consequence of insect herbivory, a number of plant biochemical processes involved in the tolerance mechanism are affected. Different studies have demonstrated a diverse functional role of various plant oxidative enzymes in protecting plants against biotic stress induced by insect herbivory. Comprehensive profiling of stress-associated plant oxidative enzymes is most relevant to successful molecular breeding of stress-tolerant crop plants. Thus, better understanding of the biochemical basis of plant defense mechanisms is imperative, not only from a basic science perspective, but also for biotechnology-based pest control practice. In this review, we emphasize the potential role of various oxidative enzymes in plant defense against insect herbivory.
The contents of total phenols and orthodihydric phenols, specific activities of polyphenol oxidase (PPO), peroxidase (PO) and catalase in leaves of powdery mildew resistant (NLM and HM 350) and susceptible (T 8 and HM 65) genotypes of fenugreek were estimated at 40, 80 and 100 days after sowing (DAS) in inoculated (E1) and natural (E2) environments. The levels of all the biochemical constituents were higher in resistant genotypes than in susceptible ones before the appearance of disease (40 DAS) in both the environments. In response to infection, an increase was observed in contents of all the parameters except catalase activity in all the genotypes. However, at higher disease severity levels of all the biochemical parameters decreased invariably in all the genotypes except activities of PPO and PO which increased further in susceptible genotypes in both the environments. The role of phenolics and oxidative enzymes in determining resistance in fenugreek against powdery mildew disease has been highlighted.
Treatment of acibenzolar-S-methyl (bionTM), salicylic acid and the saprophytic bacterium Pseudomonas fluorescens exhibited induced systemic resistance in Sorghum bicolor (cv. Rio) to Sugarcane mosaic virus (SCMV) isolates from sugarcane. The treatments significantly slowed down the SCMV titre in plants during the initial growth phase. The enhanced induction of total phenols, phenylalanine ammonia lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO) might have contributed for the induced systemic resistance triggered by various biotic and abiotic inducers. More induction of PO and PPO isozymes were noticed upon application of these inducers. In the present studies, there was a significant decrease of SCMV titre as evidenced by ELISA in these treatments. Among the treatment methods, foliar application was highly effective in case of the abiotic elicitors bion and salicylic acid whereas with P. fluorescens seed treatment was effective.
Mothbean plants (resistant and susceptible genotypes) were inoculated with
Yellow mosaic virus
(YMV) at 30 days after sowing (DAS), under controlled conditions in a naturally lit net house. Leaves samples were collected at 31, 33, 35, 37, 48 and 66 DAS and analysed for pathogenesis related enzymes and chlorophyll content.
Yellow mosaic virus
affects the activities of enzymes related to pathogenesis in mothbean even at 24 hours after inoculation. Activities of enzymes like peroxidase, polyphenol oxidase, phenylalanine ammonia lyase and tyrosine ammonia lyase were increased, whereas catalase activity was found to decrease in the leaves of inoculated plants of all the four genotypes tested, RMO 225 and HM 61 (resistant), GMO 9703 and GMO 9704 (susceptible), as compared to the uninoculated plants. Peroxidase activity increased markedly in the susceptible genotypes as compared to the resistant genotypes of inoculated plants. The activities of polyphenol oxidase showed an increasing trend in the inoculated leaves of resistant genotypes, as compared to the resistant genotypes of uninoculated ones. The results indicate that the differences between tolerance and susceptibility of hosts are quantitative as well as qualitative so defence against a pathogen entails major changes in the biochemical components of the plant. A probable role of these enzymes for defence against YMV in mothbean is discussed.
The phenolic profile and specific activity of oxidative enzymes in sorghum leaves and stem resistant and susceptible to
(Swinhoe) were analyzed at 45 and 60 days after germination. Resistant varieties had higher content of total phenols, o-dihydric phenols, flavanols and tannins than the susceptible varieties at both the stages of plant growth and the concentration of these biomolecules increased after infestation as well as with plant age in both sets of varieties. Moreover, resistant varieties exhibited higher specific activity of polyphenol oxidase, peroxidase, phenylalanine ammonia-lyase and tyrosine ammonia-lyase in their leaves and stem in comparison to the corresponding activities in susceptible ones. Peroxidase activity was several folds than the polyphenol oxidase. Healthy leaves of susceptible varieties showed higher catalase activity in comparison with resistant ones at day 45 and this trend was reversed at day 60. Role of phenolic compounds and oxidative enzymes particularly the peroxidase in determining resistance against stem borer has been high lighted.
interactions between nitric oxide donors, reactive oxygen species and
anti-oxidative defence enzymes led us to determine the activities of
anti-oxidative defence enzymes in isolated uterine smooth muscle before and
after spontaneous rhythmic activity ex vivo. For our experiments we
used isolated uteri from female Wistar rats. Our results showed an increase
in total superoxide dismutase (SOD) and Mn SOD activities in uterine smooth
muscle after spontaneous contractions when compared with non-exercised
uterine smooth muscle. The activity of catalase (CAT) and glutathione
preoxidase (GSH-Px) were also increased. No statistically significant changes
in the activities of glutathione reductase (GR) and CuZn SOD were found. It
is known that an organism's anti-oxidative defence system (guarding against
excessive reactive oxygen species generation) requires balanced increments in
its individual anti-oxidative enzyme activities rather than increases in the
activity of only some enzymes without increases in others. Thus, we may
conclude that some adaptive responses are found in exercised uterine smooth
muscle but are not complete. Therefore, our results indicate that changes in
anti-oxidative enzyme activities may influence the results of the examination
of substances ex vivo.
The main criterion that determines the quality of durum wheat is the degree of suitability for pasta production (pasta-processing quality). In this regard, pigment content and the quantity of oxidative enzymes of durum wheat play important roles in the quality of pasta. It is now possible to examine these features and specify their effects using recently developed genetic markers and spectrophotometric measurement techniques. In the present study, LOX enzyme activity and pigment content are determined using molecular and biochemical scanning. According to the obtained results, Gediz-75, Gdem-12, Line-19, Zenit, Line-7 and Line-20 were determined as the most suitable lines or varieties for the production of quality pasta with regard to LOX enzyme activity. As for pigment content, Kyle, Zenit, Gdem-12, Gdem-2, TMB-1 and TMB-3 showed the highest potential for the production of yellow pasta. When pigment content and LOX enzyme activity were evaluated together, the potential of the Gediz-75, Gdem-12 and Zenit durum wheat varieties and lines to produce yellow pasta products was shown to be very high.
The factors affecting the economically and sylviculturally disadvantageous formation of red heartwoord in beech are only partly understood. It has already been proved that at the color boundary of the red heart the total phenol concentration decreases sharply whereas the activity of oxidative enzymes (POD, PPO) increases substantially. The concentrations of (+)-catechin and (−)-epicatechin fall drastically and the five taxifolin and quercetin glycosides undergo hydrolysis. It is unclear, however, what role the flavonoids present at the boundary ((+)-catechin, (−)-epicatechin, taxifolin, and quercetin) have in the formation of the red chromophores of the heartwood. Understanding the transformation of the precursors and analysis of the products could result an enhanced utilization of redheartwood timber and better understanding of the physiology of red heartwood formation. In this work the role of catechins has been investigated by in-vitro transformation of (+)-catechin and (−)-epicatechin by extracts of beech wood enzymes. Thin-layer chromatography with scanning densitometry and acquisition of the products’ UV-visible reflection spectra proved suitable for monitoring the reactions and analyzing the products. Result have shown that rapid oxidation and oligomerization of the catechins is caused by beech enzyme extract. In-vitro products have also been compared with the chromophores of beech red heartwood. Conclusions have been drawn regarding the physiology of red heartwood formation.
Žilic , S. , Akillioglu , H.G. , Serpen , A. , Peric , V. , Gökmen , V.
2013 . Comparison of phenolic compounds, isoflavones, antioxidant capacity and oxidativeenzymes in yellow and black soybeans seed coat and dehulled bean . Eur