Developmental Effects of Sandoz 6706 on Activities of Enzymes of Phenolic and General Metabolism in Barley Shoots Grown in the Dark or under Low or High Intensity Light

Abstract

The activities of three enzymes of phenolic biosynthesis and six of general metaboUsm were studied at 24-hour intervals between the 3rd and 8th day after planting in barley shoots treated with the chlorosis-inducing herbicide Sandoz 6706 and grown in the dark or under high or low intensity Ught. The herbicide had no effect on fresh weight or soluble protein (per shoot) in plants grown in the dark or under low intensity light, but slightly decreased these parameters in plants grown for more than 5 days under high intensity light. In dark-grown seedlings the herbicide had no detectable effects on plastid ultrastructure or on the activity of malate dehydrogenase, cytochrome c oxidase, NADP-cytochrome c reductase, triose phosphate isomerase, peroxidase, catalase, shikimate dehydrogenase, phenylalanine ammonia-lyase, or chalcone-flavanone isomerase. Under low intensity light, Sandoz 6706-treated plants developed plastids with single thylakoids extending across the organelie, and the activity of al enzymes examined was increased to varying degrees. When the herbicide-treated plants were grown under high intensity Ught, plastid lamelar organization was severely disrupted. Activities of shikimate dehydrogenase and chalcone-flavanone isomerase were markedly enhanced, phenylalanine ammonia-lyase activity sUghtly promoted, and catalase activity severely inhibited. The other enzymes were not appreciably affected by Sandoz 6706 under high intensity light. It is concluded that the changes in plastid ultrastructure and enzyme activities of the herbicide-treated plants are largely secondary photomorphogenetic or photooxidative responses in the carotenoid-free plants in which chlorophylls accumulate in reduced amounts (low intensity light) or are completely absent (high intensity light).

The Fate of Chloroplast Proteins during Photooxidation in Carotenoid-Deficient Maize Leaves

“…These plastids are deficient in plastid ribosomes and lack chloroplastic proteins (18,21,28). Cytoplasmic protein synthesis and ribosome accumulation is largely unaffected (10). In spite of the absence of chloroplast development in albino seedlings, leaf morphogenesis appears to proceed normally.…”

Regulation of Plastid Gene Expression during Photooxidative Stress

“…When seedlings, in which carotenoids do not accumulate either due to a mutational or chemical block in the synthesis pathway, are transferred from permissive low light to high light, rapid bleaching occurs in the green leaf tissue (2). Bleaching of leaves in the absence of carotenoids is a symptom of a pleiotropic effect that includes the disappearance of Chl, chloroplast grana stacks, and ribosomes (2,5,30), as well as a decrease in several nuclear-and plastid-encoded chloroplast proteins (15,18,19). Light-dependent decreases in enzyme activity are limited to the chloroplast and peroxisomal compartments (3,5,12).…”

“…Bleaching of leaves in the absence of carotenoids is a symptom of a pleiotropic effect that includes the disappearance of Chl, chloroplast grana stacks, and ribosomes (2,5,30), as well as a decrease in several nuclear-and plastid-encoded chloroplast proteins (15,18,19). Light-dependent decreases in enzyme activity are limited to the chloroplast and peroxisomal compartments (3,5,12). Whereas chloroplast enzymes are much reduced in photooxidized leaves, cytoplasmic, glyoxisomal and mitochondrial enzymes are maintained at normal levels (5,26).…”

Difference in Growth, Phenolics Content and Antioxidant Activity of Cowpea Sprouts at Different Plant Parts

“…또한, Siddhuraju & Becker(2007) Chung et al, 1999). 과산화적 스트레스에 대한 적응과정 중에는 유해한 활성산소를 소거하기 위해 ascorbate peroxidase(APX), guaiacol peroxidase(GPX) 및 catalase(CAT) 등의 항산화 효소의 활성이 증가하는 것으로 알려져 있다 (Blume & McClure, 1980;Nakano and Asada, 1981). 식물 은 또한 활성 산소종에 대한 방어 기작으로 복합 항산화 시 스템을 가지고 있는데, 특히 항산화 효소의 발현은 중요한 역할을 한다 (Davies, 1995).…”