A flower-inducing substance of high molecular weight from higher plants.

The flower-inducing activities of aqueous extracts of several plants were fractionated by gel filtration. Three major peaks, corresponding to molecular weights of about 120, 20 to 30, and 5 to 10 kilodaltons, were detected in extracts of Lemna, Pharbitis, and Brassica. The latter two peaks may be degradation products generated during the extraction procedure. In extracts of soybean seeds, only the peak of material of 120 kilodaltons was detected. This is the first published report of a high molecular mass substance with florigenic activity in Lemna plants. The florigenic substance had some properties associated with proteins (or polypeptides), but the activity was unaffected by treatment with proteinase K.

Synthesis of l-(+)-Tartaric Acid from l-Ascorbic Acid via 5-Keto-d-Gluconic Acid in Grapes.

5-Keto-l-idionic acid ( identical with5-keto-d-gluconic acid, d-xylo-5-hexulosonic acid) was found as a metabolic product of l-ascorbic acid in slices of immature grapes, Vitis labrusca L. cv ;Delaware'. Specifically labeled compounds, recognized as metabolic products of l-ascorbic acid in grapes, were fed to young grape tissues to investigate the metabolic pathway from l-ascorbic acid to l-(+)-tartaric acid.Label from dehydro-l-[1-(14)C]ascorbic acid, 2-keto-l-[1-(14)C]idonic acid (l-xylo-2-hexulosonic acid), l-[1-(14)C]idonic acid, or 5-keto-l-[1-(14)C] idonic acid was incorporated into l-(+)-tartaric acid in high yields as it was in the l-[1-(14)C]ascorbic acid experiment. In a double label experiment involving a mixture of l-[1-(14)C]idonic acid and l-[2-(3)H]idonic acid, the (3)H/(14)C ratios of 5-keto-l-idonic acid and l-(+)-tartaric acid synthesized in young grape leaves were almost the same as the value of the l-idonic acid fed. Label from 5-keto-l-[6-(14)C]idonic acid was incorporated into sugars and insoluble residue in the same way as l-[6-(14)C]ascorbic acid was metabolized in grapes.These results provide strong evidence that in grapes l-(+)-tartaric acid is synthesized from the C(4) fragment that corresponds to the C1 to C4 group of the 5-keto-l-idonic acid derived from l-ascorbic acid via 2-keto-l-idonic acid and l-idonic acid.

Biosynthesis of storage proteins in developing rice seeds.

Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the starchy endosperm protein of rice (Oryza sativa L. Japonica cv Koshihikari) during seed development confirmed that storage protein begins to accumulate about 5 days after flowering. Two polypeptide groups, 22 to 23 and 37 to 39 kilodaltons, the components of glutelin, the major storage protein in rice seed, appeared 5 days after flowering. A 26-kilodalton polypeptide, the globulin component, also appeared 5 days after flowering. Smaller polypeptides (10- to 16-kilodaltons) including prolamin components, appeared about 10 days after flowering. In contrast, the levels of the 76- and 57-kilodalton polypeptides were fairly constant throughout seed development. Transmission electron microscopy and fractionation by sucrose density gradient centrifugation of the starchy endosperms at various stages of development showed that protein body type II, the accumulation site of glutelin and globulin, was formed faster than protein body type I, the accumulation site of prolamin.The 57-kilodalton polypeptide but not the glutelin subunits was labeled in a 2-hour treatment with [(14)C]leucine given between 4 and 12 days after flowering to developing ears. In vivo pulse-chase labeling studies showed the 57-kilodalton polypeptide to be a precursor of the 22 to 23 and 37 to 39 kilodalton subunits. The 57-kilodalton polypeptide was salt-soluble, but the mature glutelin subunits were almost salt insoluble.In vitro protein synthesis also showed that the mRNAs directly coding the 22 to 23 and 37 to 39 kilodalton components were absent in developing seeds and that the 57-kilodalton polypeptide was the major product. Thus, it was concluded that the two subunits of rice glutelin are formed through post-translational cleavage of the 57-kilodalton polypeptide.

Purification and characterization of acid phosphatase in aleurone particles of rice grains.

The major acid phosphatase (EC 3.1.3.2) associated with aleurone particles of rice grains (Oryza sativa L. Japonica cv. Koshihikari) was purified to homogeneous state by polyacrylamide gel electrophoresis. Its molecular weight was 72,000 when determined by gel filtration and 68,000 when found by polyacrylamide gradient gel electrophoresis in the presence of sodium dodecyl sulfate and ß-mercaptoethanol. The purified enzyme had a violet color and an absorption peak at 530 nm. Triton X-100 and lysolecithin stabilized the purified enzyme. The optimum pH for hydrolysis of p-nitrophenyl phosphate was 4.8. The enzyme hydrolyzed all inositol phosphates, several other phosphomonoesters and pyrophosphate. However, α,ß-glycerol phosphate, glucose-6-phosphate, adenosine monophosphate and inosine monophosphate were not hydrolyzed. The Km for myo-inositol hexaphosphate was 0.43 mm, which was the lowest among myo-inositol phosphates. The Km value increased as the number of phosphate linkages on myo-inositol decreased. No correlation between the maximum initial velocity (Vmax) and Km was observed. Among the myo-inositol phosphates, the Vmax for myo-inositol triphosphate was the highest. The Km for p-nitrophenyl phosphate was 1.74 mm and that for ATP was 5.26 mm. l-Tartrate, orthophosphate, molybdate and arsenate were competitive inhibitors, and F(-) was a noncompetitive inhibitor. Ag(+), Zn(2+), Hg(2+), Cu(2+) and Fe(2+) were inhibitory and the enzyme was also inactivated by preincubation with EDTA.

Ethylene formation from ethyl moiety of ethionine.

In plants, ethylene is formed in the presence of light and flavin mononucleotide from ethionine and S-ethylcysteine. The ethylene is formed from the ethyl moiety of ethionine.