Characterization of β-amylase and its deficiency in various rice cultivars

 β-Amylase deficiency in various cultivars of rice was examined at the molecular level. Using an antibody against β-amylase purified from germinating seeds of rice, we were able to demonstrate the expression and organization of the β-amylase gene in normal and deficient cultivars. Although β-amylase is a starch-hydrolyzing enzyme, as is α-amylase, the β-amylase protein/gene is expressed differently from the α-amylase protein/gene; i.e. (1) β-amylase is synthesized only in aleurone cells, (2) the enzyme production in the embryo-less half-seeds is not under hormonal control. We identified some cultivars of rice that are deficient for β-amylase activity. We present new evidence that synthesis is blocked at the level of mRNA synthesis in the deficient cultivars. The usefulness of β-amylase as a crop trait is also discussed. Received: 8 May 1998 / Accepted: 5 June 1998     

An automatic device to record the force necessary to compensate plant movements

A device, which automatically and continuously keeps moving plants in fixed positions, has been constructed. The apparatus is based on optical detection of any movements of the plant organ under study. The plant organ is kept in the desired position by means of wires, and the force necessary to apply to the wires to achieve this is recorded. The force reflects any tendency of the plant organ to move. The system is controlled by an Apple II computer. The device can work in one or two dimensions and record compensation forces in a wide range. In the experiments mentioned below, the magnitude of the forces necessary to keep the plants in a fixed position was of the order of 10^-4N.
Circadian leaf movements of Oxalis regnellii Mig. were studied in the device. The leaf rhythm continued, although the leaflets were clamped and the light input on the leaf therefore constant. Circumnutation of hypocotyls of Helianthus annus L. cv. Californicus were drastically reduced in amplitude when the hypocotyls were kept in vertical position by the wires. Since the gravitropic input signal to this system was zeroed by the equipment, the results demonstrated that in the absence of gravitropic inputs the circumnutation reactions drastically diminish. This confirmed that circumnutations of these hypocotyls are influenced by gravity. Finally, the apparatus was used to study phototropic reactions: By clamping phototropically stimulated coleoptiles of Avena sativa L. cv. Seger no gravitational stimulations were involved and the phototropic reaction without interference from gravity could be studied.     

Isolation and characterization of polymorphic microsatellites in European chestnut (Castanea sativa Mill.)

Thirteen polymorphic microsatellite loci were isolated from Castanea sativa (Mill.). Six contained dinucleotide repeats, six contained trinucleotide repeats, and one contained a compound microsatellite of a trinucleotide and a tetranucleotide repeat. The loci were characterized using C. sativa trees from three populations in the UK and the parents and six seedlings from a Turkish mapping population. The number of alleles revealed varied from two to 14 (mean = 5.15) per loci. Eight loci were found to be useful in the mapping family.     

Superoxide dismutases of chestnut leaves, Castanea sativa: Characterization and study of their involvement in natural leaf senescence

Superoxide dismutases (SOD; EC 1.15.1.1) in chestnut ( Castanea sativa Mill., cv. 431) leaves were characterized by native polyacrylamide gel electrophoresis. The three molecular forms of SOD were distinguished from each other by their different sensitivity to cyanide and H₂O₂ Three CuZn-containing SODs were detected (CuZn-SOD I, II. and III), and all the isozymes had a molecular mass of 33 kDa. CuZn-SOD III was the most abundant isozyme. whereas CuZn-SOD II was present in a minor amount. In leaves showing typical symptoms of senescence increases of 2.5-. 7- and 4-fold in the specific activities of CuZn-SODs I, II, and III. respectively, were found. In addition, the pattern of the three isozymes was modified by the age of leaves, a rise in the CuZn-SOD II and a decrease in the CuZn-SOD 1 percentages being found in senescent leaves compared to green leaves. As to other activated oxygen-related enzymes, an increase in the superoxide-generating xanthine oxidase activity and a decline in both catalase and peroxidase activities during natural senescence of chestnut leaves were observed. Results obtained suggest that in natural senescence of chestnut leaves activated oxygen species are involved, and an overproduction of hydrogen peroxide and superoxide radicals probably takes place.     

Grain or coleoptile tip as the source of IAA in cereal shoots?

Abstract. Current opinion is divided on whether the free IAA in cereal shoots is derived from the coleoptile tip or from the grain. To date these hypotheses have been considered to be mutually exclusive. In this paper the idea is advanced that both sources may function in the supply of IAA in the shoot. Critical review of the literature shows that such an explanation best fits all the available evidence. It is argued that the relative importance of each source may vary between species of the Gramineae, with the supply of IAA in Avena shoots being derived predominantly from the grain, whereas in Zea the coleoptile tip is the more important source.     

Genetic mapping identifies a rice naringenin O-glucosyltransferase that influences insect resistance

Naringenin, the biochemical precursor for predominant flavonoids in grasses, provides protection against UV damage, pathogen infection and insect feeding. To identify previously unknown loci influencing naringenin accumulation in rice (Oryza sativa), recombinant inbred lines derived from the Nipponbare and IR64 cultivars were used to map a quantitative trait locus (QTL) for naringenin abundance to a region of 50 genes on rice chromosome 7. Examination of candidate genes in the QTL confidence interval identified four predicted uridine diphosphate-dependent glucosyltransferases (Os07g31960, Os07g32010, Os07g32020 and Os07g32060). In vitro assays demonstrated that one of these genes, Os07g32020 (UGT707A3), encodes a glucosyltransferase that converts naringenin and uridine diphosphate-glucose to naringenin-7-O-β-d -glucoside. The function of Os07g32020 was verified with CRISPR/Cas9 mutant lines, which accumulated more naringenin and less naringenin-7-O-β-d -glucoside and apigenin-7-O-β-d -glucoside than wild-type Nipponbare. Expression of Os12g13800, which encodes a naringenin 7-O-methyltransferase that produces sakuranetin, was elevated in the mutant lines after treatment with methyl jasmonate and insect pests, Spodoptera litura (cotton leafworm), Oxya hyla intricata (rice grasshopper) and Nilaparvata lugens (brown planthopper), leading to a higher accumulation of sakuranetin. Feeding damage from O. hyla intricata and N. lugens was reduced on the Os07g32020 mutant lines relative to Nipponbare. Modification of the Os07g32020 gene could be used to increase the production of naringenin and sakuranetin rice flavonoids in a more targeted manner. These findings may open up new opportunities for selective breeding of this important rice metabolic trait.     

A New Enzyme “Bilirubin Oxidase” Produced by Myrothecium verrucaria MT-1

The thermal degradation kinetics of pectin methylesterase (PME) from carrot and lettuce were studied. Fresh extracts were exposed to temperatures from 55 to 70 °C until the enzyme was inactivated. A model based on the presence of two forms of the enzyme, one active and one non-active, is proposed. The natural variability of the PME activity was taken into the model in the form of normally distributed random effects. The common model parameters obtained (cleavage constant (0.0395±0.0062 s^?1), degradation constant (0.556±0.112 s^?1), cleavage energy of activation (469±23 kJ mol^?1) and degradation energy of activation (488±18 kJ mol^?1)) show that the PME degradation kinetics of the two vegetables can be explained with a single set of parameters.     

Studies on a Quantitative Analysis of Oryzalides and Oryzalic Acids in Rice Plants by GC-SIM

A procedure for the quantitative analysis of oryzalides and oryzalic acids in leaves of rice cultivars was established by using GC-MS-selective ion monitoring (GC-SIM), 17-deuterated oryzalide B being used as an internal reference. The total contents of four compounds of oryzalides and oryzalic acids in the leaves at three different growth stages of Norin-27, i.e., seedling, tillering, and ripening, showed values of 5.3, 17.9, and 37.9 μg/g, respectively. The contents of oryzalides and oryzalic acids in each organ, i.e., leaf, stem, ear, and root, showed values of 35.0 and 1.7 μg/g for the former two, respectively, and were not detectable for the latter two. A preliminary analysis of Norin-27 and Rantai emas leaves inoculated with an incompatible and compatible strain of Xanthomonas campestris pv. oryzae showed a greater accumulation of oryzalides and oryzalic acids, especially in the lesion area, than the figures for healthy leaves. Mechanical injury by a needle-bundle also increased the total amounts.     

The Action of Rice Branching Enzyme I (BEI) on Starches

The rice branching enzyme I (BEI) overproduced in Escherichia coli cells was investigated with respect to action on starches. BEI treatment decreased the turbidity of starch suspensions with distinct pasting behaviors from a native starch. This result suggests the great potential of BEI as a molecular tool for the production of a novel glucan polymer.