Constitutive and Induced Activities of Defense-Related Enzymes in Aphid-Resistant and Aphid-Susceptible Cultivars of Wheat

Abstract

Phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) are considered important biochemical markers in host plant resistance against pest insects. Constitutive activity of these enzymes was analyzed in resistant and susceptible wheat cultivars against cereal aphid Sitobion avenae (F.) at various developmental stages, i.e., tillering, stem elongation, flag leaf, and ear. Following aphid infestation, the activity of these enzymes was determined at the flag leaf and ear stages. Resistant cultivars exhibited greater constitutive PAL activity than susceptible ones at the tillering, stem elongation, and flag leaf stages. Aphid infestation enhanced levels of PAL activity in the flag leaf and ear stages in both resistant and susceptible cultivars. Constitutive PPO activity was higher in the resistant cultivars at all developmental stages. Aphid infestation induced increases in PPO activity in the flag leaf and ear stages of one susceptible cultivar, whereas induction in resistant cultivars was weaker. Resistant cultivars showed greater constitutive POD activity in the tillering, stem elongation, and flag leaf stages, while aphid infestation induced POD activity in all cultivars, especially in susceptible ones. The potential role of PAL, PPO, and POD in wheat defense against aphid infestation is discussed.

Accumulation of amino acids and phenolic compounds in biochemical plant responses to feeding of two different herbivorous arthropod pests

“…However, this phenomenon, in the case of interactions described here, requires further studies. The present data confirm the results of earlier studies, showing that changes in the rate of aromatic amino acid deamination affect the content of simple phenols, polyphenols, o-dihydroxyphenols and phenolic acids in plant tissues (Ju et al 1995;Howles et al 1996;Tovar et al 2002) and that aphid feeding modifies TAL and PAL activities (Ciepiela and Niraz 1993;Li et al 2008;Han et al 2009). PAL was also found to be activated in cucumber seedlings infested by B. tabaci and an increase of its activity was dependent on the duration of infestation .…”

“…and in wheat infested by S. avenae; moreover, resistant cultivars (cvs.) were characterised by a significantly higher PAL activity than susceptible ones (Li et al 2008;Han et al 2009). Ciepiela and Niraz (1993) observed an increase of TAL activity in wheat leaves under S. avenae infestation.…”

A gene expression analysis of syncytia laser microdissected from the roots of the Glycine max (soybean) genotype PI 548402 (Peking) undergoing a resistant reaction after infection by Heterodera glycines (soybean cyst nematode)

“…Experiments comparing varieties of wheat (Hordeum vulgare) that are resistant or susceptible to the cereal aphid (Sitobion avenae [F.]) demonstrate a higher constitutive expression of PPO in resistant varieties (Han et al 2009). However, induction of PPO occurs during both resistant and susceptible reactions (Han et al 2009).…”

Light quality affects incidence of powdery mildew, expression of defence-related genes and associated metabolism in cucumber plants

“…Meanwhile, significant changes in the activity of defence related enzymes such as phenylalanine ammonia-lyase (PAL) and polyphenoloxidase (PPO) involved in secondary metabolism have been well observed (Ye et al 2006;Han et al 2009). We have previously reported the different responses of CO 2 assimilation, chlorophyll-fluorescence quenching, expression of Calvin cycle genes and carbohydrate accumulation to light quality in Cucumis sativus ).…”