Ida Brambilla

Nitrate assimilation during the anaerobic germination of rice: expression of ferredoxin-dependent glutamate synthase

Ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC 1.4.7.1) is the last enzyme involved in the pathway of nitrate assimilation in higher plants. This paper describes the synthesis and expression of the enzyme in anaerobic coleoptiles of rice (Oryza sativa L.) and its regulation by exogenous nitrate. The activity of Fd-GOGAT was strongly inhibited by cycloheximide between 4 and 9 d of anaerobic germination. The addition of nitrate slightly increased, in the first 5 h, the specific activity of Fd-GOGAT as well as the amount of a 160-kDa protein specifically immunoprecipitated with anti-Fd-GOGAT serum. Northern blot analysis, performed with a specific riboprobe, showed the presence of mRNA of the expected size and the inductive effect of nitrate. The role of Fd-GOGAT is discussed in relation to the anaerobic assimilation of nitrate by rice coleoptiles.

Anaerobic protein synthesis and glycosylation in rice seedlings

Summary Synthesis and the polypeptide pattern of proteins and glycosylated proteins in excised roots and shoots of rice seedlings subjected to aerobic and anaerobic conditions were analyzed. In roots, the synthesis and glycosylation of proteins were more depressed by anoxia than in shoots. The synthesis of soluble proteins was, in both tissues, less inhibited by the anoxic stress than the synthesis of membrane proteins. On the contrary, the synthesis of glycosylated membrane proteins was less inhibited under anaerobic conditions than the soluble glycosylated proteins. Analysis of polypeptide patterns of proteins synthesized under nitrogen revealed some differences between root and shoot and a 35 kDa membrane glycoprotein was specifically detected in the shoots. The results are also discussed in relation to the capacity of rice shoots to undergo anaerobic growth.

Effect of Inorganic Nitrogen Nutrition (Ammonium and Nitrate) on Aerobic and Anaerobic Metabolism. in Excised Rice Roots

Summary Excised rice roots grown on ammonium and nitrate media under aerobic and anaerobic conditions were compared. In air, differences between the two culture conditions were observed in the growth of the roots and in the pattern of newly synthesized proteins. Anaerobiosis completely blocked the growth of the roots and cancelled any difference in the polypeptide pattern of newly synthesized proteins. However, in anoxia there were substantial differences in the rate and type of fermentation carried out by the roots supplied with ammonium or nitrate.

Variability in Seed Traits in a Collection of Cannabis sativa L. Genotypes

The seed of Cannabis sativa L. is an expanding source of proteins and oil for both humans and animals. In this study, the proximate composition of a collection of hemp cultivars and accessions of different geographical origins grown under the same conditions for 1 year was analyzed in order to identify potential accessions to improve hemp cultivars. Fatty acids, tocopherols, and antinutritional components, as well as concentrations of crude protein and oil were quantified. The seed oil concentrations varied between 285 and 360 g kg−1 dry seed (DS), while crude protein ranged between 316 and 356 g kg−1 dry matter (DM). The seed oil was mainly composed of unsaturated fatty acids and, as expected, the dominant fatty acids were linoleic and α-linolenic acid. A high variability among the cultivars and accessions was also detected for polyphenolic content which ranged from 5.88 to 10.63 g kg−1 DM, cv. Felina was the richest, whereas cv. Finola had the lowest polyphenolic content. Regarding antinutritional compounds in seed, a high variability was detected among all genotypes analyzed and phytic acid was particularly abundant (ranging between 43 and 75 g kg−1 DM). In conclusion, our results reveal noticeable differences among hemp seed genotypes for antinutritional components, oil and protein content. Collectively, this study suggests that the hemp seed is an interesting product in terms of protein, oil and antioxidant molecules but a reduction of phytic acid would be desirable for both humans and monogastric animals. The high variability detected among the different genotypes indicates that an improvement of hemp seed might be possible by conventional and/or molecular breeding.

Biochemical Seed Traits of Camelina sativa – An Emerging Oilseed Crop for Biofuel: Environmental and Genetic Influences

Camelina (Camelina sativa (L.) Crantz) is an attractive alternative and sustainable oilseed crop for multipurpose uses, including as a biofuel feedstock. To evaluate the value of C. sativa in Lombardia (north Italy), seven genotypes were cultivated under different climates of two consecutive years and growing seasons; quality and quantity of seed, oil, and flour were analyzed. Genotypes mainly influenced seed weight (0.98–1.56 g/1000 seeds), protein (245-401 mg/g), glucosinolates, and phytic acid. Oil content (27.5%–37.2%) and fatty acid (FA) composition varied with year and growing season among genotypes. Oils were rich in linolenic and linoleic acids (68.4%–80.8%). The monounsaturated acids ranged from 16.4%–25.6%, although erucic acid was much lower at 4.30%. Saturated FAs represented a small fraction. Low free FAs content (0.01%–0.81%) and different amounts of tocopherols (0.44-2.69 μg/mg) in oils depended on years. Correlations among seed and biochemical traits were found. Genotypes with low protein and high phytic acid contents would not be the best for flour quality. Genotypes showing high levels of protein and C18:3/C18:2 fatty acids ratio could be useful for humans and livestock. Genotype with relatively high C18:1 fatty acid content can be used mainly for biofuel production. Altogether, the data indicated that C. sativa cultivation could be promoted as an economically profitable oilseed crop in north Italian environments.