Authors:R. Arora, U. Joshi, P. Gupta, and J. Singh
): Changes in phenylalanine ammonia lyase, tyrosineammonialyase and lipoxygenase activities in the leaves of
L. infected with
. Physiol. Mol. Biol. Plants. 8, 261–266.
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.
The effect of elicitors isolated from the mycelial walls of Colletotrichum falcatum (the red rot pathogen of sugarcane) and from C. lindemuthianum (a non-pathogen) in suspension-cultured cells of sugarcane was studied. Both the elicitors induced the synthesis of enzymes of the phenylpropanoid pathway such as PAL, TAL and 4CL and also resulted in the enhanced accumulation of phenolics. However, a specific induction of the defense parameters at higher levels was recorded in suspension cells treated with the pathogen elicitor and no such differential response was observed in the case of the non-pathogen elicitor. Elicitor induced necrosis and browning of cells were observed which suggests an additional evidence that elicitors simulate pathogen infection and thus provide a valuable reason that study on elicitor induced responses may be useful in understanding the host defense mechanisms against the red rot pathogen at molecular level.
Khan, W., B. Donald L. & Smith, D.L. (2003): Chitosan and chitin oligomers increase phenylalanine ammonia-lyase and tyrosineammonia-lyase activities in soybean leaves. J. Pl. Physiol. , 160 , 859–863.