Shanti L. Mehta

Effect of drought on enzymes and free proline in rice varieties

Abstract Drought tolerant rice variety TKM-1 and susceptible variety Improved Sabarmati (I.S.) showed characteristic differences in peroxidase, RNase, nitrate r

Regulation of starch biosynthesis in normal and opaque-2 maize during endosperm development.

Abstract The absolute activities of sucrose-UDP glucosyltransferase, glucose-6-phosphate ketoisomerase and soluble and bound ADPG-starch glucosyltransferase have been studied in normal and Opaque-2 maize endosperms during development. In general, the activities of these enzymes except sucrose-UDP glucosyltransferase were higher up to 20 days post-pollination and lower at the 30 day stage in Opaque-2 than in normal maize endosperms. However, sucrose-UDP glucosyltransferase activity was higher in normal maize endosperm up to the 20 day stage while it was lower at subsequent stages than in Opaque-2. It is suggested that the lower level of these enzymes, except sucrose-UDP glucosyltransferase, might be responsible for the reduced accumulation of starch in Opaque-2 endosperm during later stages of endosperm development.

Changes in the nucleic acid and protein fractions in Opaque-2 maize kernels during development

Abstract Different RNA fractions, as well as DNA disappeared from the endosperm of Opaque-2 maize 31 days after pollination. At the same time, these nucleic acids were present in the embryo. As compared with normal maize, Opaque-2 endosperm showed high RNase activity, which increased about ten-fold 31 days after pollination. Most of the activity was due to RNase A during the early stages. The disappearance of nucleic acids from the endosperm at a critical stage might be responsible for depressed zein synthesis in Opaque-2, since little of this protein is synthesised in the earlier stages after pollination.

Peroxidase and amylase activity in developing grains of triticale, wheat and rye

Abstract Changes in the activities of peroxidase and amylase were measured during the development of grain of triticale, wheat and rye. Peroxidase and amylase activities were found to be higher in Triticale-1 which possesses highly shrivelled grains. A direct relationship between the degree to which the grain is shrivelled and the activity of peroxidase and enzymes was observed. During grain development, peroxidase and amylase activity per grain increased in Triticale-1, while it decreased in wheat, rye and well filled triticale grains.

Enzymes of starch metabolism in developing grains of high lysine barley mutant

Abstract The absolute activities of ADPG(UDPG)-pyrophosphorylase, starch phosphorylase, ADPG(UDPG)-starch synthetase, NDP-kinase and inorganic pyrophosphatase have been studied in high lysine mutant barley Notch-2 and its parent NP 113 grains during development. In general, mutant Notch-2 grains had higher average activities of UDPG-pyrophosphorylase and starch phosphorylase and lower activity of ADPG(UDPG)-starch synthetase per grain than the parent NP 113 during grain development. Activities of NDP-kinase, ADPG-pyrophosphorylase and inorganic pyrophosphatase differed only to a small extent between the mutant Notch-2 and NP 113. It is suggested that the lower activity of ADPG(UDPG)-starch synthetase might be responsible for the reduced accumulation of starch in the mutant Notch-2 grain as compared with parent NP 113 during development.

Characterization of polysomes and incorporation in vitro of leucine and lysine in normal and opaque-2 zea mays endosperm during development

Abstract Polysome preparations obtained from opaque-2 and normal maize endosperms during development did not show any significant difference in sedimentation coefficient or nucleotide composition. The pattern of incorporation in vitro of lysine and leucine, however, differed quite distinctly in these two preparations. During early stages of maturity the polysomes from opaque-2 incorporated substantially more lysine and less leucine as compared with those from normal maize. Although the trend was reversed at 25 days post-pollination, this did not result in any significant zein accumulation since very little total protein was synthesized after that stage in opaque-2 maize endosperm. It is, therefore, suggested that the opaque-2 gene exerts a regulatory control on m RNA synthesis, required for zein formation at early stages of maturation.

Changes in protein fractions and leucine-[14C] incorporation during Sorghum grain development

Abstract Incorporation of leucine and changes in different protein fractions have been studied during Sorghum grain development. Most of the label from the injected leucine-[ 14 C] was found in glutelin and residue fraction towards later stages of maturity. The label in albumin, globulin and prolamin decreased with a concomitant increase in label in glutelin and residue proteins. The concentration of lysine, aspartic acid and glycine decreased while that of leucine, proline, alanine, tyrosine, phenylalanine, and cystine increased during grain development. Increase in serine, methionine, valine and isoleucine was only marginal. The proportion of glutamic acid was high at all stages of grain development. Glutelin fraction resolved into two peaks on gel chromatography, only one of which with higher MW was labelled, while in albumin both the peaks were found to be labelled. Tannin content also increased during grain development.

Soluble and chloroplast malate dehydrogenase isoenzymes of Triticum aestivum

Abstract Three isoenzymes of malate dehydrogenase have been isolated from 9-day-old wheat shoots. The microbody (peroxisome) and chloroplast MDH are similar in their electrophoretic behaviour. The mitochondrial MDH, soluble MDH and chloroplast MDH differ in K m values for malate and NAD. The activity of MDH isoenzymes with NAD + -analogues as substrate was in the order 3-AP-NAD + > 3-AP-deam NAD + > NAD + > TN-NAD + and deam NAD + . The thermal stabilities of the isoenzymes were significantly different: C-MDH > m -MDH > S-MDH.

Changes in soluble protein and isoenzymes in normal and opaque-2 Zea mays endosperm during grain development

Abstract Electrophoretic patterns of soluble proteins, pH 5 enzyme fraction, peroxidase, glutamic dehydrogenase, leucine aminopeptidase in developing endosperm of normal and opaque-2 were studied. Multiple forms were found for all the enzymes studied. The GDH pattern showed considerable differences in normal and opaque-2 maize; the soluble protein pattern also differed, both qualitatively and quantitatively. The leucine-amino-peptidase pattern was identical and the peroxidase pattern showed slight differences.

Effect of drought on proteins and isoenzymes in rice during germination

Abstract Two drought tolerant varieties TKM-1 and TKM-2 and two drought susceptible varieties Jaya and Improved Sabarmati of rice were studied for soluble protein pattern and isoenzymes of malate dehydrogenase, glutamate dehydrogenase, esterase and peroxidase during germination at different water stress. MDH, GDH and esterase patterns were not affected, but the soluble proteins were changed. Peroxidase isoenzyme pattern from drought tolerant and susceptible varieties showed characteristic differences. The intensity of bands with higher electrophoretic mobility decreased in Jaya and Improved Sabarmati while in TKM-1 and TKM-2 the intensity of these bands did not change much after 72 hr water stress. In shoots of Jaya and Improved Sabarmati, the activity of the peroxidase isoenzymes decreased more than in TKM-1 and TKM-2 shoots with increase in water stress.