Joe H. Cherry

Increased nucleic-acid synthesis in relation to the breaking of dormancy of hazel seed by gibberellic acid

SummaryGibberellic acid breaks dormancy of hazel seeds. Markedly preceding growth of the embryonic axis is an increased RNA synthesis, as shown by total RNA determination and 32P incorporation into RNA. This increased RNA synthesis is accounted for by an increase in DNA template available for transcription and (subsequently) increased RNA polymerase activity. It is suggested that gibberellic acid breaks dormancy by a mechanism of gene derepression, as indicated by increased chromatin-directed RNA synthesis as measured in vitro.

Differences in the fatty acid composition of soybean seed produced in northern and southern areas of the U.S.A.

Abstract The fatty acid composition of soybean ( Glycine max ) seeds was sensitive to the influence of both genotype and environment. To quantify their relative environmental sensitivities, four soybean cultivars, Wells, Wayne, Cutler and Union, plus two experimental lines, 9656 and 9686, developed for lower concentrations of linolenate, were grown in Indiana (northern area) and Mississippi (southern area) in 1981. Seeds produced in the two environments were analysed for total oil content and for fatty acid composition. Seeds produced in the southern area were slightly higher (20% vs 16%) in oil content, but weighed significantly less than those produced in the north. The oil content per seed of seeds produced in the south was only 51% of the oil content of seeds produced in the north. Seeds produced in the south were significantly lower in both myristate and linolenate, but significantly higher in oleate than seeds produced in the north. Genotype by environment interactions for many oil quality measurements were largely attributable to the responses of the lines 9656 and 9686. These results indicate that higher environmental temperature reduced the linolenate concentration of soybean oil.

Nitrate uptake and utilization is modulated by exogenous γ-aminobutyric acid in Arabidopsis thaliana seedlings

Exogenously applied GABA modulates root growth by inhibition of root elongation when seedlings were grown in vitro on full-strength Murashige and Skoog (MS) salts, but root elongation was stimulated when seedlings were grown on 1/8 strength MS salts. When the concentration of single ions in MS salts was individually varied, the control of growth between inhibition and stimulation was found to be related to the level of nitrate (NO(3)(-)) in the growth medium. At NO(3)(-) concentrations below 40 mM (full-strength MS salts level), root growth was stimulated by the addition of GABA to the growth medium; whereas at concentrations above 40 mM NO(3)(-), the addition of GABA to the growth medium inhibited root elongation. GABA promoted NO(3)(-) uptake at low NO(3)(-), while GABA inhibited NO(3)(-) uptake at high NO(3)(-). Activities of several enzymes involved in nitrogen and carbon metabolism including nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (NADH-GOGAT), NADP-dependent isocitrate dehydrogenase (NADP-ICDH), and phosphoenol pyruvate carboxylase (PEPCase) were regulated by GABA in the growth medium. Supplementing 1/8 strength MS medium with 50 mM GABA enhanced the activities of all of the above enzymes except ICDH activities in root tissues. However, at full-strength MS, GABA showed no inhibitory effect on the activities of these enzymes, except on GS in both root and shoot tissues, and PEPCase activity in shoot tissues. Exogenous GABA increased the amount of NR protein rather than its activation status in the tissues. This study shows that GABA affects the growth of Arabidopsis, possibly by acting as a signaling molecule, modulating the activity of enzymes involved in primary nitrogen metabolism and nitrate uptake.

Changes in leucyl- and tyrosyl-tRNA of soybean cotyledons during plant growth.

Abstract 1. 1. Soybean cotyledons were used to determine changes in leucyl- and tyrosyl-tRNAs with seedling age. Two of the six leucyl-tRNAs from cotyledons quantitatively increase with age, between 2 and 15 days. Tyrosyl-tRNA, which is separable into three fractions, shows a sharp decrease in Species 2 and a simultaneous increase in Species 3 over the same period of time. 2. 2. Treatment of seeds with a cytokinin had no effect on the tyrosyl-tRNAs, but accelerated the age-related changes which occur in leucyl-tRNAs. 3. 3. It is concluded that as the soybean cotyledons are depleted of their storage materials and begin to senesce, quantitative changes in leucyl- and tyrosyl-tRNA ensue. The significance of these changes in relation to senescence is discussed.

Purification and characterization of glutamate decarboxylase from cowpea

Abstract Glutamate decarboxylase (GAD) was purified 300-fold from green cowpea ( Vigna unguiculata L.) pods using a combination of PEG precipitation, DEAE cellulose chromatography, hydroxylapatite chromatography, and Q-resin chromatography. The partially purified preparation demonstrated 2 primary bands in SDS-polyacrylamide gel electrophoresis with up to 3 additional minor bands. Cowpea GAD has a pH optimum at between pH 5.5–6.0, and an apparent K M for glutamate of 3.2 mM at pH 5.8. Both crude GAD preparations and preparations partially purified through the hydroxylapatite step can be stimulated by Ca 2+ and calmodulin when assayed at pH 5.8. However, the purified enzyme does not show activation by Ca 2+ and/or calmodulin at pH 5.8 or at pH 7.0.

Studies on messenger RNA from peanut plants: In vitro polyribosome formation and protein synthesis

Preparations from cotyledons of unimbibed peanut seed show a low level of amino acid incorporation into protein. Similar preparations from imbibed seed exhibit increased activity. RNA extracted from germinating peanut cotyledons and then eluted after ribosomal RNA on the methylated albumin-kieselguhr (MAK) column had the highest template activity. This fraction stimulates amino acid incorporation into protein in an in vitro system. Isolated messenger RNA binds to monoribosomes obtained from dry seed and the polyribosomes thus produced are active in protein synthesis. It is suggested from these results that native mRNA from peanut cotyledons forms a stable complex with monoribosomes in the presence of Mg2+. The reaction does not require an ATP energy source or 105 000 ×g supernatant enzymes.

Characterization of nucleic acids in peanut cotyledons

Methylated albumin column chromatography was used to fractionate nucleic acids from peanut cotyledons. Six nucleic acid fractions were characterized by their 32 P turnover, effect of actinomycin D on synthesis and their association with subcellular fractions.

Purification and characterization of acetyl-CoA carboxylase from developing soybean seeds☆

Abstract Acetyl-CoA carboxylase from two lines of soybean ( Glycine max ) seeds has been purified to apparent homogeneity. The procedure included affinity chromatography of the enzyme on avidin-monomer-Sepharose 4B. The enzyme from both lines showed a single band on polyacrylamide gel electrophoresis. On sodium dodecyl sulphatepolyacrylamide gel electrophoresis, the enzyme from experimental line 9686 showed a single protein band having the M , 240 000. The enzyme from the commercial line Wayne, however, showed three protein bands having the M , s 240 000, 65 000 and 58 000, respectively. High concentrations of the enzyme were required for stability as well as the presence of dithiothreitol, glycerol and Triton X-100. The enzyme was active over a wide pH range, with an optimum at 8.2 for 9686 and 7.5 for Wayne. The enzyme from both 9686 and Wayne showed absolute specificity for acetyl-CoA as a substrate and this could not be replaced by propionyl-CoA, butyryl-CoA, hexanoyl-CoA or S-methylerotonyl-CoA. At the optimum pH the apparent K m values for the substrates were: bicarbonate, 1.13 mM; acetyl-CoA, 0.32 mM; ATP, 0.46 mM for the Wayne carboxylase and bicarbonate, 1.56 mM; acetyl-CoA, 0.17 mM; ATP, 0.14 mM for the 9686 enzyme. Citrate, at higher concentrations, was strongly inhibitory. Both ADP and AMP inhibited the enzyme from 9686 and Wayne. The enzyme from both 9686 and Wayne did not appear to be highly regulated by cellular metabolites.

Characterization of acetyl-CoA carboxylase in the seed of two soybean genotypes☆

Abstract Changes in the activity of acetyl-CoA carboxylase was followed during the formation of two lines of soybean ( Glycine max .) seeds. The acetyl-CoA carboxylase activity expressed as units/seed was found to be higher in the experimental variety 9686 than in the cultivar, Wayne. The maximum activity in 9686 was around 40 days after flowering (DAF), while in Wayne it was around 30 DAF. The enzyme was active over a wide pH range, with an optimum at 8.2 for 9686 and 7.5 for Wayne. Citrate below 3 mM bad no effect on 9686 enzyme, but higher concentrations were inhibitory. In Wayne, an increase in citrate up to 5 mM slightly stimulated the enzyme but higher concentrations were strongly inhibitory. Mn 2+ could not replace Mg 2+ as an essential activator of the carboxylase in both Wayne and 9686. A differential regulation of acetyl-CoA carboxylase in the two lines of soybean is suggested.

RNA synthesis and the germination of light-sensitive lettuce seeds.

SummaryThe germination of lettuce seeds is inhibited by the nucleotide base analogue 6-methylpurine. RNA synthesis has been measured during imbibition and germination as 32P-phosphate incorporation into RNA species as fractionated by polyacrylamide gel electrophoresis. Seeds were surface sterilized and imbibed in the presence of various antibiotics. RNA preparations from lettuce seeds were coelectrophoresed with 3H-RNA prepared from bacteria to check for bacterial contamination of the seeds. There is a much higher rate of RNA synthesis in illuminated, germinating seeds as compared to dark, non-germinating seeds. This difference does not develop until after 12 hours of imbibition at 27°, which is the time of onset of germination and radicle growth.