Differential radiosensitivity of seeds,seedlings and callus cultures of Petunia inflata

A comparative study of the effects of γ-irradiation on seeds, seedlings and callus cultures of Petunia inflata showed striking differences in radiosensitivity as reflected in differences in mean fresh and dry weights, seedling height and morphology. Seeds subjected to low doses (4–6 kR) of irradiation showed stimulation of seedling height. Direct exposure of seedlings to high doses (10 kR) of irradiation caused inhibition in their development. Callus cultures, however, were more radioresistant compared to seeds and seedlings. Tissues grown on either an irradiated nutrient medium or on a medium in which sucrose alone had been irradiated, showed a marked inhibition in their growth potential.     

Structural analysis of free N-glycans occurring in soybean seedlings and dry seeds

The structures of unconjugated or free N-glycans in stems of soybean seedlings and dry seeds have been identified. The free N-glycans were extracted from the stems of seedlings or defatted dry seeds. After desalting by two kinds of ion-exchange chromatography and a gel filtration, the free N-glycans were coupled with 2-aminopyridine. The resulting fluorescence-labeled (PA-) N-glycans were purified by gel filtration, Con A affinity chromatography, reverse-phase HPLC, and size-fractionation HPLC. The structures of the PA-sugar chains purified were analyzed by the combination of two-dimensional sugar chain mapping, jack bean alpha-mannosidase digestion, alpha-1,2-mannosidase digestions, partial acetolysis, and ESI-MS/MS. The free N-glycan structures found showed that two categories of free N-glycans occur in the stems of soybean seedlings. One is a high-mannose type structure having one GlcNAc residue at the reducing end (Man 9 approximately 5 GlcNAc1, 93%), that would be derived by endo-GM (Kimura, Y. et al., Biochim. Biophys. Acta, 1381, 27-36 (1998)). The other small component is a xylose-containing type one having two GlcNAc residues at the reducing end (Man3Xyl1GlcNAc2, 7%), which would be derived by PNGase-GM (Kimura, Y. and Ohno, A., Biosci. Biotechnol. Biochem., 62, 412-418 (1998)). The detailed structural analysis of free glycans showed that high-mannose type free N-glycans (Man 9 approximately 5 GlcNAc1) in the soybean seedlings have a common core structural unit; Manalpha1-6(Man1-3)Manalpha1-6(Manalpha1-3)Ma nbeta1-4GlcNAc. Comparing the amount of free N-glycans in the seedling stems and dry seeds, the amount in the stems of seedlings was much higher than that in the dry seeds; approximately 700 pmol per one stem, 8 pmol in one dry seed. This fact suggested that free N-glycans in soybean seedlings could be produced by two kinds of N-glycan releasing enzymes during germination or seedling-development.     

Amylase protein inhibitors and the role of Aegilops species in polyploid wheat speciation

Protein inhibitors extracted with water from seeds of Triticum and genetically related species were characterized according to their apparent molecular weights, electrophoretic mobilities and their specificities in inhibiting α-amylases from human saliva and Tenebrio molitor L. larvae. No detectable amylase inhibition activity was found in extracts from diploid wheats, whereas in all tetraploid and hexaploid wheats as well as in the Aegilops species tested we found several amylase inhibitor groups of different molecular weights. In each group, several inhibitor components slightly different in their electrophoretic mobilities, but identical in their inhibition behaviour toward amylases from different origins have been shown. Both from the qualitative and quantitative standpoints, amylase protein inhibitors from hexaploid wheats were the summation of those from tetraploid wheats plus the ones from Aegilops squarrosa. Amylase inhibitors from Aegilops speltoides largely differed from those extracted from tetraploid wheats as well as from all the amylase inhibitors described in plant seeds up to now. These results indicate a relevant homology between the amylase inhibitor coding genes of the D wheat genome and those of the D Aegilops genome and confirm that Ae. squarrosa is the donor of the whole D genome to hexaploid wheats. They also suggest that Ae. speltoides is not the donor of the B genome to polyploid wheats, although a not yet identified Aegilops species might be such a donor.     

Possible chromosomal location of genes determining the osmoregulation of wheat

Summary Stress-induced free amino acid accumulation in the presence of 0.7 M mannitol has been compared in tissue cultures of moderately stress-tolerant Chinese Spring and stress-sensitive Cappelle Desprez cultivars and in disomic chromosome substitution lines of Cappelle Desprez into Chinese Spring. The profile of amino acid accumulation was different in the two parents. The amino acid concentration of the substitution lines belonging to the A, B and D genomes, respectively, altered characteristically under stress condition. The Cappelle Desprez chromosomes associated with non-ionic osmotic stress-induced free amino acid accumulation were 5A and 5D.     

Subgenomic analysis of microRNAs in polyploid wheat

In this study, a survey of miRNAs using the next-generation sequencing data was performed at subgenomic level. After analyzing shotgun sequences from chromosome 4A of bread wheat (Triticum aestivum L.), a total of 68 different miRNAs were predicted in silico, of which 37 were identified in wheat for the first time. The long arm of the chromosome was found to harbor a higher variety (51) and representation (3,928) of miRNAs compared with the short arm (49; 2,226). Out of the 68 miRNAs, 32 were detected to be common to both arms, revealing the presence of separate miRNA clusters in the two chromosome arms. The differences in degree of representation of the different miRNAs were found to be highly variable, ranging 592-fold, which may have an effect on target regulation. Targets were retrieved for 62 (out of 68) of wheat-specific, newly identified miRNAs indicated that fundamental aspects of plant morphology such as height and flowering were predicted to be affected. In silico expression blast analysis indicated 24 (out of 68) were found to give hits to expressed sequences. This is the first report of species- and chromosome-specific miRNAs.     

Proteomic analysis and extensive protein identification from dry, germinating Arabidopsis seeds and young seedlings

Proteins accumulated in dry, stratified Arabidopsis seeds or young seedlings, totaled 1100 to 1300 depending on the time of sampling, were analyzed by using immobilized pH gradient 2-DE gel electrophoresis. The molecular identities of 437 polypeptides, encoded by 355 independent genes, were determined by MALDI-TOF or TOF-TOF mass spectrometry. In the sum, 293 were present at all stages and 95 were accumulated during the time of radicle protrusion while another 18 appeared in later stages. Further analysis showed that 226 of the identified polypeptides could be located in different metabolic pathways. Proteins involved in carbohydrate, energy and amino acid metabolism constituted to about 1/4, and those involved in metabolism of vitamins and cofactors constituted for about 3 % of the total signal intensity in gels prepared from 72 h seedlings. Enzymes related to genetic information processing increased very quickly during early imbibition and reached highest level around 30 h of germination.     

Evidence for a role of calcium in nitrate assimilation in wheat seedlings

Severely Ca-deficient Triticum aestivum L. seedlings accumulated high levels of nitrite and moderate levels of nitrate and organic nitrogen, but contained unaltered levels of hydroxylamine. Nitrite accumulation was not related to molybdenum deficiency, or altered cellular pH. Nitrate reductase was decreased by Ca deficiency, apparently by repression of enzyme synthesis from accumulated nitrite and not by inhibition of enzyme activity. Nitrite reductase and NADP diaphorase activities were not affected by Ca deficiency, and Ca did not restore activity to nitrite reductase inactivated by cyanide. The results indicated that the role of Ca is in intracellular transport of nitrite and not in induction or activity of enzymes.     

盐胁迫对冬小麦幼苗干物质分配和生理生态特性的影响

以冬小麦(Triticum aestivum L.)品种周麦18(Zhoumai18)和豫麦49(Yumai49)为材料,采用盆栽培养,研究100、250、350 mmol/L和450 mmol/L NaCl 浓度胁迫下,小麦幼苗干物质分配、根系特征、叶绿素含量、游离脯氨酸含量和根系活力变化规律.结果表明,随着盐分浓度的增加,两个品种小麦的叶面积、地上干重以及根的长度显著减小;根系干重、根直径、根表面积、根体积、根系活力以及叶绿素含量呈先上升后下降趋势,在250 mmol/L NaCl处理下达最大.叶绿素a/b随NaCl浓度升高而上升.随盐分浓度变化周麦18叶片游离脯氨酸含量高而变化幅度大,450mmol/L处理组的含量高于对照组1.5倍.供试品种冬小麦耐盐阈值为250～350 mmol/L.     

The effect of the biochemical adaptations in the Manchu alder (Duschecia fruticosa (Rupr)) to an elevated natural radiation background on the survivability of seedlings and on the radiosensitivity of its seeds

Seeds and sprouts of bushy alder existing for long under the condition of the enhances natural radiation background (ENRB; from 1.4 to 72.0 mCu/(kg.s)) have been examined to determine biochemical adaptations to permanent low-level irradiation. To achieve this goal a combined cytological and biochemical technique for the assessment of the activity of genome of the sprout root meristem in response to translation, replication and reparation has been applied. The activity of antioxidant systems has been studied. The data obtained allow us to reveal mechanisms of alder bush biochemical adaptations to various ENRB rates and their effect upon seeds radiosensitivity and sprouts survival. It is determined that the increase in sprout vitality and high radioresistance of seeds ripened under the conditions of low-level natural radiation is due to the content of low molecular antioxidants and activation of systems of genome reparation.