A novel wheat alpha-amylase gene (alpha-Amy3)

Summary A genomic clone of a wheat -amylase gene (Amy3/33) was identified, on the basis of hybridisation properties, as different from -Amy1 and -Amy2 genes which had been characterised previously. The nucleotide sequence revealed that this gene has the normal sequence motifs of an active gene and an open reading frame interrupted by two introns. The protein sequence encoded by this open reading frame is recognisably similar to that of -amylase from the -Amy1 and -Amy2 genes and there is high sequence homology in all three proteins at the putative active sites and Ca⁺⁺ binding region. In addition, the introns are at positions equivalent to the position of introns in the -Amy1 and -Amy2 genes. However, the sequence was less similar to -Amy1 and -Amy2 than these are to each other. Southern blot analysis showed that the Amy3/33 DNA is one of a small multigene family carried on a different chromosome (group 5) from either the -Amy1 or -Amy2 genes. A further difference from the -Amy1 and -Amy2 genes was the pattern of expression. Amy3/33 was expressed only in immature grains and, unlike the -Amy1 and -Amy2 genes, not at all in germinating aleurones. These data suggested therefore that this gene represents a third type of -amylase gene, not described before, which shares a common evolutionary ancestor with the -Amy1 and -Amy2 genes.     

Factors affecting the photoproduction of ammonia from dinitrogen and water by the cyanobacterium Anabaena sp. strain ATCC 33047

Synthesis of ammonia from dinitrogen and water by suspensions of Anabaena sp. Strain ATCC 33047 treated with the glutamine synthetase inhibitor L-methionine-D,L-sulfoximine is strictly dependent on light. Under otherwise optimal conditions, the yield of ammonia production is influenced by irradiance, as well as by the density, depth, and turbulence of the cell suspension. The interaction among these factors seems to determine the actual amount of light available to each single cell or filament in the suspension for the photoproduction process. Under convenient illumination, the limiting factor in the synthesis of ammonia seems to be the cellular nitrogenase activity level, but under limiting light conditions the limiting factor could, however, be the assimilatory power required for nitrogen fixation. Photosynthetic ammonia production from atmospheric nitrogen and water can operate with an efficiency of ca. 10% of its theoretical maximum, representing a remarkable process for the conversion of light energy into chemical energy.     

Photocontrol of Dark Circadian Rhythms in Stomata of Phaseolus vulgaris L

Stomatal diffusion resistance in primary leaves of Phaseolus vulgaris L. which had been grown in light:dark cycles followed a marked circadian rhythm when the plants were transferred to continuous darkness. Reentrainment of the rhythm required more than one inductive change in photoperiod. The phasing of the rhythm of dark stomatal opening was contolled primarily by the light-on (dawn) signal, whereas the rhythm of dark closure was related to the light-off (dusk) signal. The evidence points to a dual control of the circadian clock in which a product of photosynthesis plays a major role. No evidence for phytochrome involvement in the phasing of the rhythm was found. An influence of phytochrome on the amplitude of the stomatal rhythm was observed in which removal of phytochrome-far-red absorbing form caused rapid damping.     

Photosynthetic Activity in the Flower Buds of ;Valencia' Orange (Citrus sinensis [L.] Osbeck)

Flower buds of `Valencia' orange (Citrus sinensis [L.] Osbeck) were able to fix ¹⁴CO₂ into a number of compounds in their own tissues under both light and dark conditions. The total incorporation, however, was about 4-fold higher in the light than in the dark. In the light, 50% of the total ¹⁴C label was found in the neutral fraction (sugars), 22% in the basic fraction (amino acids), and 26% in the acid-1 fraction (organic acids). In the dark, about 95% of the ¹⁴C label was incorporated into the basic and acid-1 fractions. Activities of ribulose bisphosphate carboxylase and phosphoenolpyruvate carboxylase (expressed in micromoles CO₂ per milligram protein per hour) averaged 1.95 and 8.87 for the flower buds, and 28.5 and 3.6 for the leaves, respectively. The ability of orange flower buds to fix ambient CO₂ into different compounds suggests that this CO₂ assimilation may have some regulatory role during the early reproductive stages in determining citrus fruit initiation and setting.     

Simultaneous reactivation of ultraviolet damage in xanthium leaves

Experiments on Xanthium leaf discs were carried out to determine whether concomitant photoreactivation could be detected and if so, to compare its effects with photoreactivation due to post-irradiation treatments. Attempts mere made to simulate certain intensities of unfiltered solar radiation. A small but definite amount of simultaneous reactivation was observed. The dose reduction factor averaged 0.57. It was not clear whether the reactivation was due mainly to direct photoreactivation, photoprotection, or to heating effects. A much larger amount of reactivation due to post-irradiation treatments (direct photoreactivation) was noted with the dose reduction factor averaging 0.30.     

Soluble peroxidase from winter wheat seedlings with phenoloxidase-like activity

Peroxidase isozymes from winter wheat (Triticum aestivum L. cv Orso) seedlings extracts showed phenoloxidase-like activity, becoming visible on polyacrylamide gels also in the absence of hydrogen peroxide. The results obtained after a characterization of the two activities, based on their substrate specificity, on their selective inhibition, and on the possible occurrence of artifacts, suggested the existence of polyfunctional peroxidase isozymes. Different isozymes possessing only phenol oxidase activity were not found in the same plant material. This appears to be the first evidence of phenoloxidase-acting isoperoxidases in winter wheat.     

Seroconversion of recipient ewes after transfer of ova exposed to Brucella ovis in vitro

Zona pellucida-intact ova collected from ewes seronegative to Brucella ovis were exposed in vitro to B ovis and washed 10 times in medium that contained no antibiotics. After exposure and washing, nontransferable ova were cultured for isolation of Brucella , and the viable ova were transferred into seven B ovis seronegative ewes. No pregnancies resulted, thus recipient ewes were bred during the next breeding season, and blood samples were collected for bacteriological and serological examination until one month after lambing. Brucella ovis was isolated from all of the nontransferable ova, indicating that the transferred ova had viable organisms adhered to them. Although no recipient was found to be pregnant at Day 45, all seven ewes responded to the transferred ova by producing anti-Brucella antibodies. With the exception of a ewe that was euthanized early in the project due to a traumatic injury, all recipients lambed normally during the following breeding season. Brucella was not found in any sample collected from ewes or lambs. However, ELISA titers for B ovis remained in the suspicious range and a ewe was positive on the CF test within 2 wk of lambing.