Pisum

About: Pisum is a research topic. Over the lifetime, 1688 publications have been published within this topic receiving 35167 citations.

Superoxide Dismutases: I. Occurrence in Higher Plants

Abstract: Shoots, roots, and seeds of corn (Zea mays L., cv. Michigan 500), oats (Avena sativa L., cv. Au Sable), and peas (Pisum sativum L., cv. Wando) were analyzed for their superoxide dismutase content using a photochemical assay system consisting of methionine, riboflavin, and p-nitro blue tetrazolium. The enzyme is present in the shoots, roots, and seeds of the three species. On a dry weight basis, shoots contain more enzyme than roots. In seeds, the enzyme is present in both the embryo and the storage tissue. Electrophoresis indicated a total of 10 distinct forms of the enzyme. Corn contained seven of these forms and oats three. Peas contained one of the corn and two of the oat enzymes. Nine of the enzyme activities were eliminated with cyanide treatment suggesting that they may be cupro-zinc enzymes, whereas one was cyanide-resistant and may be a manganese enzyme. Some of the leaf superoxide dismutases were found primarily in mitochondria or chloroplasts. Peroxidases at high concentrations interfere with the assay. In test tube assays of crude extracts from seedlings, the interference was negligible. On gels, however, peroxidases may account for two of the 10 superoxide dismutase forms.

Subcellular distribution of multiple forms of glutathione reductase in leaves of pea (Pisum sativum L.).

Abstract: On sodium-dodecyl-sulfate polyacrylamide gels, purified glutathione reductase (GR; EC 1.6.4.2) from the leaves of two- to three-week-old pea (Pisum sativum L. cv. Birte) seedlings was represented by a single band with an apparent molecular weight of 55 kilodaltons. This polypeptide was resolved to multiple isoforms by two-dimensional electrophoresis. Fractionation of protoplasts and purification of subcellular organelles has shown that enzyme activity is associated with the chloroplasts, mitochondria and cytosol (in this order, approx. 77%, 3%, and 20% of the total activity). Distinct multiple isoforms of the enzyme, which differed in isoelectric point and were compartment-specific, were resolved from purified mitochondria and chloroplasts. The latency of the glutathione reductase activity which co-purified on Percoll gradients with the mitochondrial marker enzyme, cytochrome-c oxidase (EC 1.9.3.1.), indicated that this enzyme was within the mitochondrion. The mitochondrial glutathione reductase activity was strongly dependent on NADPH and not NADH.

Light-stimulated transcription of genes for two chloroplast polypeptides in isolated pea leaf nuclei.

Abstract: Nuclei isolated from both light-grown and dark-grown leaves of Pisum sativum by Percoll density gradient centrifugation incorporate labelled UTP into RNA when supplemented with the other three nucleoside triphosphates. The RNA is heterodisperse, with transcripts up to at least 25S in size. Among these transcripts are sequences hybridizing to cloned DNA probes for wheat rRNA and two abundant chloroplast polypeptides of Pisum, viz. the small subunit of ribulose bisphosphate carboxylase and a polypeptide of the light-harvesting chlorophyll a/b binding complex. Transcription of small subunit and light-harvesting complex sequences is greater (18-fold and 9-fold, respectively) in nuclei from light-grown leaves than in nuclei from dark-grown leaves. Transcription of ribosomal genes, by contrast, is only doubled by growth in the light. Small subunit and light-harvesting complex sequences transcribed in dark-grown nuclei are not degraded in a 120 min chase. These results suggest that the stimulation of accumulation of small subunit and light-harvesting complex mRNAs by exposure of Pisum seedlings to light is mediated by an increase in transcription rather than by a decrease in RNA degradation.