Isolation of legumin-like protein from Phaseolus aureus and Phaseolus vulgaris

An 11S seed globulin has been isolated from Phaseolus aureus and P. vulgaris by zonal isoelectric precipitation and the MWs of the constituent subunits determined. The protein of P. vulgaris occurs in the protein body fraction and its chemical composition, including the N-terminal amino acids and amino acid composition has been determined. The similarity between the 11S globulin of the two Phaseolus spp. and legumin from other leguines is discussed.     

Arabinogalactan from Phaseolus atropurpureus leaves

Water-soluble polysaccharide material comprising d-galactose (53·0%), l-arabinose (33·2%) and d-glucuronic acid (13·8%) has been isolated from the leaves of Phaseolus atropurpureus. Acid hydrolysis, periodate oxidation and methylation have indicated a highly branched structure. The principal interglycosidic linkages have been tentatively identified as 1,3- and 1,6-linked d-galactopyranose and 1,3-linked l-arabinofuranose residues. In synthesising polysaccharide with these structural features, P. atropurpureus differs from other legumes such as soybean, lucerne and Centrosema.     

Starch synthesis in isolated Phaseolus vulgaris chloroplasts

Isolated bean (Phaseolus vulgaris) chloroplasts were used to investigate the mode of synthesis of transitory amylose and amylopectin from ADP-glucose. Pulse chase experiments showed that labelled glucose in amylose decreased when chased with cold substrate as compared to controls. A significant portion of this decrease appeared in the amylopectin fraction indicating that amylopectin was formed from amylose. However, time course experiments showed that the rate of amytopectin synthesis is higher than that of amylose at the early stages of incubation, suggesting a certain degree of independent synthesis of the two fractions. High concentration of citrate increased the rate of amylopectin synthesis.     

Protein-polysaccharide linkages in glycoproteins from Phaseolus vulgaris

Serine and hydroxyproline participate in protein-polysaccharide linkages in hydroxyproline-poor glycoproteins from Phaseolus vulgaris cv Pinto. Most substituted hydroxyproline residues contain arabinose, galactose and glucose, but some have arabinose only. Serine residues contain arabinose, galactose and glucose.     

Early biochemical events during adventitious root initiation in the hypocotyl of Phaseolus vulgaris

Indole butyric acid (IBA) initiates roots in the hypocotyl tissue of Phaseolus vulgaris (French bean). The response is dependent on the concentration of IBA and the duration of exposure to the hormone. IBA enhances the rate of total protein synthesis in ca 30 min after exposure of the hypocotyl segments to the hormone. There is no detectable change in total or poly(A)-containing RNA synthesis in this period although significant increases are seen 2 hr after hormone pre-treatment. The early IBA-mediated increase in protein synthesis (30 min) is not sensitive to Actinomycin D but the antibiotic blocks the increase manifested 2 hr after hormone pre-treatment. Inhibition of early protein synthesis by cycloheximide depresses and delays root initiation. Cytosol prepared from IBA-treated hypocotyl tissue stimulates protein synthesis in vitro to a greater extent than that of the control.     

Invertase and auxin-induced elongation in internodal segments of Phaseolus vulgaris

A close positive correlation was observed between segment elongation and the specific activity of soluble acid invertase in stem segments of P. vulgaris incubated for 21 hr in the presence of IAA or of several synthetic auxins and auxin analogues. Optimum concentrations for the stimulation of growth and invertase activity were similar and varied from 10^?6 M (2,4-D) through 10^?5 M (IAA, IBA, α-NAA, β-NAA) to greater than 10^?4 (IPA, PoAA, trans-cinnamic acid). The weak activity of trans-cinnamic acid, a competitive inhibitor of auxin action, may have resulted from cis-trans isomerization during incubation. The concentration of hexose sugars in the segments fell during incubation in the presence of auxin, the greatest decline in hexose concentration occurring in the presence of compounds exhibiting the greatest stimulation of growth.     

Epoxidase/epoxide hydrase activity in cell cultures of Phaseolus vulgaris

The presence of epoxidase and epoxide hydrase enzymes in cell suspension culture of Phaseolus vulgaris is demonstrated. Results indicate high levels of enzyme activity using stilbene and stilbene oxide as substrates.     

Variation in low molecular weight carbohydrate composition of Phaseolus vulgaris seeds

Variations in the low M_r, carbohydrate composition have been observed in wild forms of common bean (Phaseolus vulgaris) seed. In four of 23 samples, verbascose content in the seeds was quite high and the ratio verbascose—stachyose was more than 1.0. This type of carbohydrate composition was named type A, and has a much higher verbascose content and lower galactinol and stachyose content than the rest of the wild forms, named type B. Although the total and individual carbohydrate content, with the exception of the verbascose content, of the cultivated forms of the common bean were higher than those of wild forms, the carbohydrate composition of the cultivated forms was essentially similar to type B of the wild forms. This carbohydrate composition was considered to be basic to the species.     

Enzymic formation of carbonyls from linoleic acid in leaves of Phaseolus vulgaris

Homogenization of Phaseolus vulgaris leaves at acid pH results in the evolution of hexanal, cis-3- and trans-2-hexenal. With cell-free extracts of leaves, linoleic and linolenic acids are enzymically converted to their hydroperoxides (predominantly the 13-hydroperoxide isomers) and to hexanal or hexenal respectively. Activity was highest in young, dark-green leaves and was stimulated by Triton X-100. Oleic acid is not a substrate for these reactions. Both 9- and 13-hydroperoxides were cleaved to carbonyl fragments and are proposed as intermediates in the formation of volatile aldehydes and non-volatile ω-oxoacids in P. vulgaris leaves. Properties of the enzyme systems are described.     

Biosynthesis of the phytoalexin phaseollin in Phaseolus vulgaris

Feeding experiments in CuCl₂-treated French bean (Phaseolus vulgaris) seedlings have demonstrated that labelled 2′,4′,4-trihydroxychalcone, daidzein, 7,2′,4′-trihydroxyisoflavone, 3,9-dihydroxypterocarpan and phaseollidin are all good precursors of the pterocarpan phytoalexin phaseollin. These compounds represent a logical sequence in the biosynthetic pathway to phaseollin.     

Primary metabolites of Phaseolus vulgaris nodules

More ethanol soluble material (carbohydrate and amino nitrogen) was found in both host cell and bacteroid components of Phaseolus vulgaris nodules from plants grown at 28 W/m² than from plants grown at 7 W/m². The range of compounds identified was similar at the two irradiances. On feeding ¹⁴CO₂ to the plant tops at either irradiance the labelling patterns of carbohydrates and organic acids in the nodule host cells and bacteroids suggested that any or all of the following substances could be donated by the host to the bacteroids for general metabolism: sucrose, fructose, glucose, an unidentified carbohydrate, malic acid and an organic acid co-chromatographing with 6-phosphogluconate. Distribution and labelling patterns of nodule amino compounds were consistent with the hypothesis that ammonia is the primary product of nitrogen fixation within bacteroids, and that this ammonia is transported to host cells for assimilation, initially into glutamine and glutamate.     

Comparison of globulin proteins from Phaseolus vulgaris with those from Vicia faba

Extraction of maturing Phaseolus vulgaris seeds with an ascorbic acid—NaCI medium facilitated the preparation of two globulin fractions which wer     

Cyclic nucleotide phosphodiesterase activity in Phaseolus vulgaris

Centrifugal fractionation showed that 70% of the cyclic nucleotide phosphodiesterase activity of Phaseolus vulgaris seedlings is recovered in the 1     

Phytoalexin formation in cell suspensions of Phaseolus vulgaris in response to an extract of bean hypocotyls

Suspension cultures of Phaseolus vulgaris accumulated phytoalexins after treatment with an extract of bean hypocotyls. Maximum production of phaseollin occurred during the early exponential phase of culture growth. Phaseollin was converted to phaseollinosoflavan by these cultures and this conversion occurred during accumulation of the phytoalexins. Factors affecting phytoalexin accumulation in these cultures are discussed.     

Cell wall hydroxyproline-polysaccharide associations in Lupinus hypocotyls

Extraction of lupin hypocotyl cell walls with guanidine thiocynate, both before and after dilute acid treatment does not dissolve the hydroxyproline indicating that compounds containing this amino acid are probably covalently linked to insoluble wall constituents other than through acid labile arabinofuranose-hydroxyproline links. Dilute alkali does extract all of the wall hydroxyproline largely as non-dialysable material. Sequential extraction of cell walls with alkali at two temperatures (2° and 22–25°) removes most of the hemicellulose at the lower temperature but only dissolves the hydroxyproline at the higher temperature. Other studies show that the hydroxyproline containing polymer is co-precipitated with hemicellulose-B arabino-xylan. When cell walls from elongating and non-elongating hypocotyl sections are compared using this sequential extraction, the hemicellulose-B arabino-xylan containing hydroxyproline from the non-elongating wall has a much higher proportion of arabinoseand galactose than the same polymer from the elongating wall. Much more of the hydroxyproline from the elongating wall is dialysable. These results indicate more bonding of the hydroxyproline-containing glycoprotein within the wall of non-elongating tissue consistent with its suggested role in stopping cell elongation. It is suggested that the glycoprotein is linked to insoluble wall constituents such as cellulose through galactose or by direct protein to cellulose links.     

Metabolism of abscisic acid and the occurrence of epi-dihydrophaseic acid in Phaseolus vulgaris

When (±)-abscisic acid-[2-¹⁴C] or (±)-abscisic acid-[4′-¹⁸O] was fed to bean (Phaseolus vulgaris) shoots, phaseic acid (PA) and dihydrophaseic acid (DPA) were the major metabolites, while epi-dihydrophaseic acid (epi-DPA) appeared as a minor metabolite. In the acidic fraction the amount of epi-DPA ranged from 18 to 42% of the DPA content, in the conjugated form from 50 to 200%. The content of endogenous epi-DPA amounted to only 1–2% of that of the DPA. These data indicate that the applied abscisic acid is not metabolised in a manner identical with that of the endogenous material. DPA and epi-DPA were shown to be formed separately from PA and could not be inter-converted either by the extraction conditions employed or when fed to bean shoots during short term experiments.     

The function of the pentose phosphate pathway in Phaseolus mungo hypocotyls

The metabolism of d-gluconate-[1-¹⁴C] and -[6-¹⁴C] by segments from etiolated hypocotyls of Phaseolus mungo has been studied. The release of ¹⁴CO₂ from gluconate-[1-¹⁴C] was greater than that from gluconate-[6-¹⁴C] in all parts of hypocotyls examined. Incorporation of the radioactivity from gluconate-[6-¹⁴C] into RNA, lignin and aromatic amino acid fractions was greater in the upper (younger) part of the hypocotyls. Incorporation into sugars was greater in the lower (more mature) parts.     

Characterization of an enzyme from Phaseolus vulgaris seeds which hydroxylates GAi to GA8

Hydroxylation of gibberellin-[³H] A₁ (GA₁-[³H]) to GA₈-[³H] by the 95000 g supernatant fluid from imbibed bean seeds required Fe²⁺ or Fe³⁺ and O₂ but was insensitive to CO. The hydroxylating enzyme has a sedimentation coefficient of 4·5 S, and was precipitated by (NH₄)₂SO₄ at 35–60% saturation. This hydroxylase was specific for GA₁ and did not hydroxylate either pseudo-GA₁-[³H] or 16-ketoGA₁-[³H]. Virtually all hydroxylase activity was localized in the cotyledons.     

Metabolism of phaseollin by Septoria nodorum and other non-pathogens of Phaseolus vulgaris

Phaseollin is metabolised by cultures of Septoria nodorum, a non-pathogen of bean, into cis and trans isomers of 12,13-dihydrodihydroxyphaseollin. These products are much less fungitoxic than phaseollin which suggests that the capacity to detoxify phytoalexins is not confined to pathogenic fungi.