Free sterol and phospholipid evolution in Triticum aestivum seedlings at optimum and low temperatures

The free sterol and phospholipid of the leaves and roots of Triticum aestivum var. MEC seedlings, grown at different temperatures, were determined. During growth, free sterols increased in the leaves and roots at optimum temperature (21°) whereas in the cold treatment (1°) they remained significantly unchanged despite an increase of cholesterol of the leaves indicating a higher degree of regulation of membrane structure under cold conditions. Phospholipid from both groups of plants increased in the leaves and in the roots during all the experimental period, although at a lower degree in the cold treated plants. The molar ratio of free sterol/phospholipids suggested a less ordered membrane structure in the cold treated leaves and roots.     

Partial purification and properties of nuclease 1 from barley malt

A sugar-unspecific nuclease has been purified 260-fold from barley malt diastase. The enzyme, a glycoprotein of 37 000 MW, is highly active on single-stranded polynucleotides at pH 5–6. The nuclease is inhibited by several adenine nucleotides, and it binds weakly to NADP-agarose and ATP-agarose.     

Effects of NADH and thiol compounds on wheat leaf nitrate reductase

The initial activity of wheat leaf nitrate reductase was depressed on inclusion of the following thiol compounds; dithiothreitol, dithioerythreitol or mercaptoethanol, but not cysteine and glutathione. This thiol effect simply resulted from an interference with the chemical determination of nitrite. Preincubation of the enzyme with NAD⁺ and these thiols enhanced the inhibition of nitrate reductase activity. This effect was mediated by NADH production by the thiol reduction of NAD⁺. The inactivation by NAD⁺ in the presence of thiol compounds which was enhanced by cyanide ions could be reversed by ferricyanide, as has been observed previously for NADH-mediated inactivation of nitrate reductase.     

Flavonol glucosyltransferase activity in Bronze embryos of Zea mays

The major UDPG: flavonol glucosyltransferase (UFGT) in maize is an enzyme of strict positional specificity known to be coded by the Bz locus. In bz mature endosperms, no UFGT can be detected. However, bz embryos possess a residual flavonol glucosyltransferase activity which is independent of Bz locus control. The products of this activity have been identified as the 3′-, 7- and 3-glucosides.     

Purification and characterization of an alpha-glucosidase from germinating millet seeds

An α-glucosidase (α-d-glucoside glucohydrolase, EC 3.2.1.20) was isolated from germinating millet (Panicum miliaceum L.) seeds by a procedure that included ammonium sulfate fractionation, chromatography on CM-cellulofine/Fractogel EMD SO₃, Sephacryl S-200 HR and TSK gel Phenyl-5 PW, and preparative isoelectric focusing. The enzyme was homogenous by SDS-PAGE. The molecular weight of the enzyme was estimated to be 86,000 based on its mobility in SDS-PAGE and 80,000 based on gel filtration with TSKgel super SW 3000, which showed that it was composed of a single unit. The isoelectric point of the enzyme was 8.3. The enzyme readily hydrolyzed maltose, malto-oligosaccharides, and α-1,4-glucan, but hydrolyzed polysaccharides more rapidly than maltose. The K_m value decreased with an increase in the molecular weight of the substrate. The value for maltoheptaose was about 4-fold lower than that for maltose. The enzyme preferably hydrolyzed amylopectin in starch, but also readily hydrolyzed nigerose, which has an α-1,3-glucosidic linkage and exists as an abnormal linkage in the structure of starch. In particular, the enzyme readily hydrolyzed millet starch from germinating seeds that had been degraded to some extent.     

Identification and heritability of fumonisin insensitivity in Zea mays

Landraces of maize (Zea mays ssp. mays) and its wild teosinte relatives (Zea mays spp. parviglumis and mexicana) were surveyed for sensitivity to fumonisin B(1), a phytotoxin produced by the maize pathogen Gibberella moniliformis. Only two of 42 Z. mays samples were highly insensitive to FB(1) (ED(50) = ca. 200 microM). The teosintes and 76% of the maize landraces were moderately or highly sensitive to FB(1) (ED(50) < or = 30 microM), which indicates that FB(1) sensitivity is likely to be an ancestral trait in Z. mays. F(1) generations derived from crosses between FB(1)-sensitive maize inbred B73 and insensitive landraces were significantly less sensitive than B73. Thus, our data indicate that FB(1)-insensitivity is a relatively rare but heritable trait in maize. We also report the sensitivity of maize to other Gibberella toxins - beauvericin, diacetoxyscirpenol, and moniliformin.     

Wound-induced green leaf volatiles cause the release of acetylated derivatives and a terpenoid in maize

Green leaf volatiles (GLVs), generally occurring C6 alcohols, aldehydes and acetates from plants, play an important role in plant-plant communication. These compounds induce intact plants to produce jasmonic acid, and induce defense-related gene expression and the release of volatile compounds. Here, we address wound-induced GLVs cause the release of acetylated derivatives and a terpenoid, (E)-4,8-dimethylnona-1,3,7-triene (DMNT) in intact maize, which may be a type of plant-plant interaction mediated by airborne GLVs. Upon exposure of intact maize seedlings to wound-induced GLVs, (Z)-3-hexenyl acetate was consistently the most abundant compound released. Exogenous application of individual alcohols and aldehydes mostly resulted in the release of corresponding acetate esters. C6-alcohols with a double bond between the second and third, or the third and fourth carbon atoms, C5- or C6-aldehydes, and (Z)-3-hexenyl acetate triggered the release of DMNT. When (Z)-3-hexenyl acetate and hexyl acetate were used to treat maize seedlings, they were recovered from the plants. These data demonstrated that: (1) apart from direct adsorption and re-release of acetate esters, absorption and conversion of exogenous alcohols and aldehydes into acetate esters occurred, and (2) DMNT was induced by a range of aldehydes and unsaturated alcohols.     

Relationships among low MW hydrophobic proteins from wheat endosperm

Low MW proteins extractable with chloroform-methanol mixtures from wheat endosperm have been purified from different Triticum species and partially characterized. Their amino acid composition and MWs are consistent with previous genetic evidence concerning relationships among these proteins: proteins CM1 and CM2 are homoeologous (ancestral homologues); proteins CM3 and CM3′ are allelic variants; proteins 16 and 17 are homoeologous.     

The control of lysine biosynthesis in maize

Aspartate kinase has been partially purified and characterised from germinating maize seedlings. The K_m for aspartate was 9 mM. Out of several amino acids which are potential feedback regulators of the enzymes, only lysine is markedly inhibitory, having a K_i of 13 μM and causing 100% inhibition at 0.5 mM. Lysine also protects the enzyme against heat inactivation. Dihydrodipicolinic acid synthase isolated from the same tissue is also inhibited by lysine, 1 mM causing 95% inhibition.     

On the identity of Festuca jubata Lowe (Poaceae) and the description of a new Festuca species in the Azores Islands

The majority of authors consider Festuca jubata Lowe as an endemic species common to Madeira and the Azores. Saint-Yves proposed that F. jubata was an Azorean endemic and described a geovicarious taxon in Madeira: F. filiformis C. Sm. ex Link in Buch ssp. mandonii St.-Yves. We undertook a complete bibliographical revision of the taxonomy, nomenclature, and chorology of F. jubata s.l. , and contrasted it with morphological and anatomical studies performed on samples from the Azores and Madeira. Azorean plants usually identified as F. jubata had a character combination distinct from that of those with a Madeiran provenance. Saint-Yves' proposal of two independent taxa was correct, but he erroneously considered F. jubata as an Azorean endemic because the name F. jubata was based on Madeiran plants. Consequently, F. jubata auct. pl. from the Azores belongs to a new species.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 493–499.