Chromosome damage induced by artificial seed aging in barley

Summary Barley (Hordeum vulgare L. Himalaya) seeds were artificially aged under two storage conditions (32 °C/12% moisture content (m.c.) and 38 °C/18% m.c.) to study the behavior of induced chromosomal aberrations during plant growth. The frequencies of aberrant anaphases at first mitosis in root tips were correlated with loss of germinability. However, after 3 and 5 weeks' growth, aberration frequency declined. In plants grown from artificially aged seeds, the frequency of aberrant anaphases appeared to be stabilized at about 1% after 5 weeks' growth, in spite of the large differences in the frequencies at first mitosis. This suggests that because of their genetic imbalance, cells with chromosomal aberrations induced by seed aging were being excluded during plant growth. Meiotic chromosome configurations at MI were normal (7 II) in all plants studied, although a few precocious separations were found. Meiotic aberrations were found at AI-TI, AII-TII and the tetrad stages in the pollen mother cells of plants grown from the control and artificially aged seeds. However, there were no clear differences among the control and the two aging treatments. It was obvious that some cells with meiotic chromosomal aberrations were lost between the AI-TI and AII-TII stages, and still more between the AII-TII and tetrad stages. The frequency of tetrads with micronuclei in plants produced from artificially aged seeds was the same as in the control. The plants grown from artificially aged seeds showed high pollen fertility (95.2 to 97.0%) and seed fertility (90.1 to 97.2%) which was comparable to the control values (97.4 and 97.9%) respectively, indicating no special effects of seed aging. Anaphase cells of the first mitosis in the next (A₂) generation were analyzed to study the transmission of chromosomal aberrations through mitotic and meiotic cell divisions in the A₁ generation. Aberrant anaphases in the progeny from the artificially aged seeds were not higher than those of the control progeny. This indicates that the chromosomal aberrations induced by seed aging are not transmitted to the next generation.Published with the approval of the Director of the Colorado state Experiment Station as Scientific Series No. 2776     

A comparison of fens in natural and artificial landscapes

Fens depend on inputs of groundwater or surface water. In Western Europe especially soligenous fens, receiving groundwater, are threatened by human hydrological intervention. We demonstrate the impact of artificial versus natural hydrologies on such fens by comparing 3 case areas: the Biebrza valley (reference) and the Gorecht and Vecht river plains (both reclaimed and drained). The patterns found in the fairly undisturbed Biebrza area suggest local water quality is governed by a strong regional groundwater flow emerging in the fen near the valley margins and seeping through it down to the river. Hence water quality gradients are smooth: there is little variation in water type over large distances. The pattern is determined by the natural geomorphology. In the reclaimed Vecht and Gorecht river plains large differences exist at short distance. Regional water flow from the adjacent ridges into the plains is weak here and governed primarily by water management (polders and pumping wells). However, the relations between specific water types and fen species and communities in this artificial pattern are quite similar to those found in the natural landscape. Low-productive rich fens are fed by calcium-rich and base-rich, nutrient-poor groundwater in both cases. While conservation of such rich fens is served best by maintaining the natural groundwater flow, some opportunities for restoration with an artificial hydrology are discussed.     

Monthly population density and structure patterns of an endangered seahorse Hippocampus capensis: a comparison between natural and artificial habitats

This study investigated aspects of the population ecology of the endangered Knysna seahorse Hippocampus capensis within different habitat types. High densities of H. capensis were found within artificial Reno mattress habitat, within the Knysna Estuary, South Africa. Monthly surveys at three sites were conducted from October 2015 to August 2016 to compare population densities of H. capensis in this artificial habitat with natural eel grass Zostera capensis habitat. Hippocampus capensis densities varied significantly across all sites and highest population densities were consistently observed within the Reno mattress habitat. Hippocampus capensis were also found to be significantly larger within the Reno mattress habitat and pooled data showed that males were significantly larger than females. The overall sex ratio for all three sites was female biased, although this varied across seasons at two sites. The findings suggest that artificial Reno mattresses provide novel habitat for this endangered species and consideration should be given to the usefulness of these structures in future conservation actions.     

The basis of natural and artificial postzygotic hybridization barriers in Arabidopsis species

The success or failure of interspecific crosses is vital to evolution and to agriculture, but much remains to be learned about the nature of hybridization barriers. Several mechanisms have been proposed to explain postzygotic barriers, including negative interactions between diverged sequences, global genome rearrangements, and widespread epigenetic reprogramming. Another explanation is imbalance of paternally and maternally imprinted genes in the endosperm. Interspecific crosses between diploid Arabidopsis thaliana as the seed parent and tetraploid Arabidopsis arenosa as the pollen parent produced seeds that aborted with the same paternal excess endosperm phenotype seen in crosses between diploid and hexaploid A. thaliana. Doubling maternal ploidy restored seed viability and normal endosperm morphology. However, substituting a hypomethylated tetraploid A. thaliana seed parent reestablished the hybridization barrier by causing seed abortion and a lethal paternal excess phenotype. We conclude from these findings that the dominant cause of seed abortion in the diploid A. thaliana x tetraploid A. arenosa cross is parental genomic imbalance. Our results also demonstrate that manipulation of DNA methylation can be sufficient to erect hybridization barriers, offering a potential mechanism for speciation and a means of controlling gene flow between species.     

Resource distribution and the trade-off between seed number and seed weight: a comparison across crop species

In grain crops, total sink capacity is usually analysed in terms of two components, seed number and individual seed weight. Seed number and potential individual seed weight are established at a similar timing, around the flowering period, and seed weight at maturity is highly correlated with the potential established earlier. It is known that, within a species, available resources during the seed set period are distributed between both yield components, resulting in a trade-off between seed number and seed weight. Here we tested if this concept could apply for interspecific comparisons, where combinations of numbers and size across species could be related to the total available resources being either allocated to more seed or larger potential individual seed weight during the seed set period. Based on this, species differences in seed weight should be related to resource availability per seed around the period when seed number is determined. Resource availability per seed was estimated as the rate of increase in aboveground biomass per seed around the period of seed set. Data from 15 crop species differing in plant growth, seed number, seed weight and seed composition were analysed from available literature. Because species differed in seed composition, seed weight was analysed following an energy requirement approach. There was an interspecific trade-off relationship between seed number per unit of land area and seed weight (r = 0.92; F(1, 13) = 32.9; n = 15; P < 0.001). Seed weight of different species was positively correlated (r = 0.90; F(1, 13) = 52.9; n = 15; P < 0.001) with resource availability per seed around the seed set period. This correlation included contrasting species like quinoa (Chenopodium quinoa; ∼100000 seeds m⁻², ∼4 mg equivalent-glucose seed⁻¹) or peanut (Arachis hypogaea; ∼800 seeds m⁻², ∼1000 mg equivalent-glucose seed⁻¹). Seed number and individual seed weight combinations across species were related and could be explained considering resource availability when plants are adjusting their seed number to the growth environment and seeds are establishing their storage capacity. Available resources around the seed set period are proportionally allocated to produce either many small seeds or few larger seeds depending on the particular species.     

Analysis of natural allelic variation of Arabidopsis seed germination and seed longevity traits between the accessions Landsberg erecta and Shakdara, using a new recombinant inbred line population

Quantitative trait loci (QTL) mapping was used to identify loci controlling various aspects of seed longevity during storage and germination. Similar locations for QTLs controlling different traits might be an indication for a common genetic control of such traits. For this analysis we used a new recombinant inbred line population derived from a cross between the accessions Landsberg erecta (Ler) and Shakdara (Sha). A set of 114 F9 recombinant inbred lines was genotyped with 65 polymerase chain reaction-based markers and the phenotypic marker erecta. The traits analyzed were dormancy, speed of germination, seed sugar content, seed germination after a controlled deterioration test, hydrogen peroxide (H2O2) treatment, and on abscisic acid. Furthermore, the effects of heat stress, salt (NaCl) stress, osmotic (mannitol) stress, and natural aging were analyzed. For all traits one or more QTLs were identified, with some QTLs for different traits colocating. The relevance of colocation for mechanisms underlying the various traits is discussed.     

Exploring nitrogen remobilization for seed filling using natural variation in Arabidopsis thaliana

Nineteen Arabidopsis accessions grown at low (LOW N) and high (HIGH N) nitrate supplies were labelled using (15)N to trace nitrogen remobilization to the seeds. Effects of genotype and nutrition were examined. Nitrate availability affected biomass and yield, and highly modified the nitrogen concentration in the dry remains. Surprisingly, variations of one-seed dry weight (DW(1S)) and harvest index (HI) were poorly affected by nutrition. Nitrogen harvest index (NHI) was highly correlated with HI and showed that nitrogen use efficiency (NUE) was increased at LOW N. Nitrogen remobilization efficiency (NRE), as (15)N partitioning in seeds ((15)NHI), was also higher at LOW N. The relative specific abundance (RSA) in seeds and whole plants indicated that the (14)NO(3) absorbed post-labelling was mainly allocated to the seeds (SEEDS) at LOW N, but to the dry remains (DR) at HIGH N. Nitrogen concentration (N%) in the DR was then 4-fold higher at HIGH N compared with LOW N, whilst N% in seeds was poorly modified. Although NHI and (15)NHI were highly correlated to HI, significant variations in NUE and NRE were identified using normalization to HI. New insights provided in this report are helpful for the comprehension of NUE and NRE concepts in Arabidopsis as well as in crops and especially in Brassica napus.     

Genetic and molecular characterization of embryonic mutants identified following seed transformation in Arabidopsis

Over 5000 transgenic families of Arabidopsis thaliana produced following seed transformation with Agrobacterium tumefaciens were screened for embryonic lethals, defectives, and pattern mutants. One hundred and seventy-eight mutants with a wide range of developmental abnormalities were identified. Forty-one mutants appear from genetic studies to be tagged (36% of the 115 mutants examined in detail). Mapping with visible markers demonstrated that mutant genes were randomly distributed throughout the genome. Seven mutant families appeared to contain chromosomal translocations because the mutant genes exhibited linkage to visible markers on two different chromosomes. Chromosomal rearrangements may therefore be widespread following seed transformation. DNA gel blot hybridizations with 34 tagged mutants and three T-DNA probes revealed a wide range of insertion patterns. Models of T-DNA structure at each mutant locus were constructed to facilitate gene isolation. The value of such models was demonstrated by using plasmid rescue to clone flanking plant DNA from four tagged mutants. Further analysis of genes isolated from these insertional mutants should help to elucidate the relationship between gene function and plant embryogenesis.     

Sex and aging: A comparison between two phenoptotic phenomena

Phenoptosis is a phenomenon that is genetically programmed and favored by natural selection, and that determines death or increased risk of death (fitness reduction) for the individual that manifests it. Aging, here defined as agerelated progressive mortality increase in the wild, if programmed and favored by natural selection, falls within the definition of phenoptosis. Sexual reproduction (sex), as for the involved individuals determines fitness reduction and, in some species, even certain death, also falls within the definition of phenoptosis. In this review, sex and aging are analyzed as phenoptotic phenomena, and the similarities between them are investigated. In particular, from a theoretical standpoint, the genes that cause and regulate these phenomena: (i) require analyses that consider both individual and supra-individual selection because they are harmful in terms of individual selection, but advantageous (that is, favored by natural selection) in particular conditions of supra-individual selection; (ii) determine a higher velocity of and greater opportunities for evolution and, therefore, greater evolutionary potential (evolvability); (iii) are advantageous under ecological conditions of K-selection and with finite populations; (iv) are disadvantageous (that is, not favored by natural selection) under ecological conditions of r-selection and with unlimited populations; (v) are not advantageous in all ecological conditions and, so, species that reproduce asexually or species that do not age are predicted and exist.     

Proteome-wide Analysis of Protein Thermal Stability in the Model Higher Plant Arabidopsis thaliana

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Highlights

• •Over 1700 Arabidopsis proteins with thermal models in multiple replicates.
• •Melting temperature correlates with 1°, 2°, and 3° protein characteristics.
• •Ligand-induced thermal shifts are evident in complex protein extracts.

     

植物种子老化的生理学研究进展

种子品质的优劣对于农牧业生产、经济与遗传资源有效利用、生物多样性保护以及植物群落恢复与重建具有重要的作用.种子老化是其在贮藏过程中普遍存在的一种生理现象,是随着种子贮藏时间延长而发生和发展的自然不可逆过程,不仅关系到后续种、苗生长与产量、品质等问题,还对植物种质资源的保存、利用和开发等均具有重要影响.种子老化的生理机制...     

Analysis of natural allelic variation at seed dormancy loci of Arabidopsis thaliana

Arabidopsis accessions differ largely in their seed dormancy behavior. To understand the genetic basis of this intraspecific variation we analyzed two accessions: the laboratory strain Landsberg erecta (Ler) with low dormancy and the strong-dormancy accession Cape Verde Islands (Cvi). We used a quantitative trait loci (QTL) mapping approach to identify loci affecting the after-ripening requirement measured as the number of days of seed dry storage required to reach 50% germination. Thus, seven QTL were identified and named delay of germination (DOG) 1-7. To confirm and characterize these loci, we developed 12 near-isogenic lines carrying single and double Cvi introgression fragments in a Ler genetic background. The analysis of these lines for germination in water confirmed four QTL (DOG1, DOG2, DOG3, and DOG6) as showing large additive effects in Ler background. In addition, it was found that DOG1 and DOG3 genetically interact, the strong dormancy determined by DOG1-Cvi alleles depending on DOG3-Ler alleles. These genotypes were further characterized for seed dormancy/germination behavior in five other test conditions, including seed coat removal, gibberellins, and an abscisic acid biosynthesis inhibitor. The role of the Ler/Cvi allelic variation in affecting dormancy is discussed in the context of current knowledge of Arabidopsis germination.     

人工老化对老芒麦种子活力和生理生化变化的影响

以4份老芒麦种子为试验材料,利用100%RH高温高湿老化法(AA)对老芒麦种子进行不同梯度的老化处理,探讨老化后老芒麦种子活力和种子内部生理生化的变化。结果表明:随着老化程度的加深,4份老芒麦种子的各项活力指标均出现明显下降趋势;生理生化指标中,种子浸出液电导率出现先下降后缓慢上升、可溶性糖含量呈现先减少后增加的现象,而丙二醛含量则出现整体一致的上升趋势,POD活性变化无规则,SOD活性出现先增加后减小的现象,CAT活性则发生整体下降的趋势。本研究结果将为老芒麦种质资源的保护和遗传完整性的研究提供基础理论依据。     

Vertical jumping reorganization with aging: a kinematic comparison between young and elderly men

To our knowledge jumping kinematics have never been studied in elderly persons. This study was aimed at examining the influence of aging on vertical jump performance and on interjoint coordination. Two groups of adults, 11 young men ages 18-25 years and 11 older men ages 79-100 years, were filmed while performing a maximal squat jump. Compared to young adults, jump height was significantly decreased by 28 cm in the elderly. Older adults spontaneously jumped from a more extended position of the hip. Results showed a decrease in hip, knee, and ankle linear velocity and angular amplitude with aging. The decrease in jump height was attributed to a decrease in explosive force and in the range of shortening of extensor muscles. In agreement with the literature, a proximo-distal coordination pattern was observed in young adults. Older adults used a simultaneous pattern. This may indicate that adults adjust their pattern of joint coordination as they age.     

Isolation and characterization of thermophilic bacteria from natural and artificial habitats

Several thermophilic Bacillus Strains were isolated from natural as well as artificial habitats. They grow optimally on a carbohydrate-containing medium at a temperature of 65 to 68°C and a pH value of 6 to 7 under aerobic conditions. They utilize glucose, sucrose and sodium acetate as carbon and energy sources. They can be differentiated by acid formation and composition of intracellular fatty acid fraction as well as growth on xylose, lactose, starch, cellobiose, ribose and galactose.     

Bed bugs,their blood sources and life history parameters: a comparison of artificial and natural feeding

A blood‐feeding system that utilizes a small amount of whole heparinized human blood in parafilm bags is described in detail, and similarities and differences between artificially fed and naturally rodent‐fed bed bugs (Hemiptera: Cimicidae) are discussed. Blood with high levels of heparin (10%) was unsuitable for artificial colony rearing, whereas bed bugs fed on 1% heparinized blood and those that naturally ingested rat blood completed their lifecycle with similar stage structures over time, with no significant differences in mortality. No differences in feeding efficiency or fertility were found in a direct comparison of bed bugs maintained under each of these two treatments, but analysis of the full lifecycle revealed that artificially fed bed bugs became significantly smaller and laid fewer eggs than rodent‐fed bed bugs. The level of membrane stretching regulated the number of bed bugs that fed. When the membrane was stretched to twice its length and width, 96% of bed bugs successfully fed through the parafilm. Whole heparinized blood that was stored at 6 °C for ≥ 14 days failed to retain its nutritional value and the amount of blood consumed and number of consecutive moults were significantly reduced.     

Proteomic investigation of natural variation between Arabidopsis ecotypes

Two-dimensional (2-D) gel electrophoresis and peptide mass fingerprinting were used to investigate the natural variation in the proteome among 8 Arabidopsis thaliana ecotypes, of which 3 were previously shown to display atypical responses to environmental stress. Comparison of 2-D maps demonstrated that only one-quarter of spots was shared by all accessions. On the other hand, only 15% of the 25 majors spots accounting for half the total protein amount could be classified as major spots in all ecotypes. Identification of these major spots demonstrated large differences between the major functions detected. Accordingly, the proteomes appeared to reveal important variations in terms of function between ecotypes. Hierarchical clustering of proteomes according to either the amount of all anonymous spots, that of the 25 major spots or the functions of these major spots identified the same classes of ecotypes, and grouped the three atypical ecotypes. It is proposed that proteome comparison has the capacity to evidence differences in the physiological status of ecotypes. Results are discussed with respect to the possibility to infer such differences from limited comparisons of major proteins. It is concluded that classical proteomics could constitute a powerful tool to mine the biodiversity between ecotypes of a single plant species.     

A comparison of diatom community structure on natural and artificial substrata

Artificial substrata have been used in diatom studies for almost 100 years. However, concern still exists over whether diatom communities developing on artificial substrata accurately represent communities developing on natural substrata. This study compares the diatom communities colonising glass slides and clay tiles in two coastal dune lakes, and compares these communities to the naturally occurring communities in the epipelon, epilithon, and epiphyton. Both glass microslides and clay tiles, incubated for three separate periods ranging from 29 to 68 days, resulted in replicate substratum samples supporting similar diatom community compositions at each site. The degree of variation between artificial substrata communities at different sites, and between the two artificial substrata types, was generally no more than the degree of variation between communities on different types of natural substrata. Additionally, the composition of the diatom communities on the artificial substrata was representative of the community composition on the natural substrata. The effects of incubation period and siting are discussed.