Transgenic Arabidopsis plants expressing Escherichia coli pyrophosphatase display both altered carbon partitioning in their source leaves and reduced photosynthetic activity

The effects of the cytosolic expression of Escherichia coli pyrophosphatase (ppa) were investigated in the rosette leaves of transgenic Arabidopsis plants. During the daytime, glucose and fructose were found to accumulate at levels that were approximately two- to threefold higher in these plants than in the wild type. Interestingly, however, neither sucrose nor starch levels showed any distinctive build up in transgenic plants except under continuous white light growth conditions, during which they accumulated at high levels. Additionally, the leaves of transgenic Arabidopsis plants contain two- to threefold higher levels of inorganic phosphate (Pi) and two- to sixfold higher levels of uridine diphosphate-glucose than wild type plants during the diurnal cycle. In contrast, triose phosphate contents in the leaves of E. coli ppa transformants were either similar or slightly decreased when compared with wild type leaves. Furthermore, the photosynthetic activity of these transgenic plants was found to be reduced by 20–40% compared to normal levels. These results indicate that induction of ppa activity in the cytosol affects carbon partitioning between source and sink organs and also that the concomitant increase in Pi caused the accumulation of carbon metabolites and reduced photosynthetic activity.     

The pattern of carbon allocation supporting growth of preformed shoot primordia in Acomastylis rossii (Rosaceae)

Extreme preformation, the initiation of leaves or inflorescences more than 1 yr before maturation and function, is common in arctic and alpine habitats. This extended pattern of development provides a potential means to alleviate an apparent asynchrony between carbon supplied by photosynthesis in the summer and carbon demanded by growth in the spring. Allocation of resources to preforming organs has not been studied in herbs with multi-year patterns of preformation. Acomastylis rossii (Rosaceae) in the southern Rockies initiates leaves and inflorescences 2 yr prior to their maturation and function. Allocation to preforming organs in A. rossii was studied by means of a labeled carbon pulse chase experiment. During the summer, carbon is allocated directly to preforming organs and rhizomes from the mature leaves. Additional allocation of carbohydrate into preforming organs occurs in autumn after photosynthesis by mature leaves has ceased. Organ primordia initiated in the second year do not receive a substantial quantity of the labeled carbon from reserves stored in the rhizome the previous year. We conclude that concurrent photosynthesis is the primary source of carbon for preformation development.     

米老排人工林碳素积累特征及其分配格局

在生物量调查的基础上,对桂西南地区28年生米老排人工林生态系统的碳素积累特征及分配格局进行了研究.结果表明:米老排各器官碳含量在522.8～560.2 g·kg-1,大小排序为:树叶(560.2 g·kg-1)＞树干(542.8 g·kg-1)＞树根(530.9 g·kg-1)＞树皮(530.8 g·kg-1)＞树枝(522.8 g·kg-1);土壤碳含量以表土层最高,且随土层深度的增加而降低;米老排人工林乔木层碳贮量为147.90 t·hm-2,其中,树干占乔木层碳贮量的63.72％;米老排人工林生态系统碳贮量为285.36 t·hm-2,各组分的分配顺序为乔木层＞土壤层＞凋落物层＞灌木层＞草本层;植被层碳贮量为土壤层(0～100 cm)的1.1倍.     

Resource capture, biomass allocation and growth in herbaceous plants

Plant species differ widely in their rate of biomass production, even when grown under optimal conditions. A key question concerns the extent to which these growth rates correlate with the uptake of carbon and nitrogen and with the biomass allocation between leaves and roots. Recent data show that the answer to this question differs for mono- and dicotyledons, and that more than biomass allocation, it is the ratio between the activities of leaves and roots that correlates with the growth rate of a plant.     

The effect of time-varying mortality and carbon assimilation on models of carbon allocation in annual plants

Summary Models of optimal carbon allocation schedules have influenced the way plant ecologists think about life history evolution, particularly for annual plants. The present study asks (1) how, within the framework of these models, are their predictions affected by within-season variation in mortality and carbon assimilation rates?; and (2) what are the consequences of these prediction changes for empirical tests of the models? A companion paper examines the basic assumptions of the models themselves. I conducted a series of numerical experiments with a simple carbon allocation model. Results suggest that both qualitative and quantitative predictions can sometimes be sensitive to parameter values for net assimilation rate and mortality: for some parameter values, both the time and size at onset of reproduction, as well as the number of reproductive intervals, vary considerably as a result of small variations in these parameters. For other parameter values, small variations in the parameters result in only small changes in predicted phenotype, but these have very large fitness consequences. Satisfactory empirical tests are thus likely to require much accuracy in parameter estimates. The effort required for parameter estimation imposes a practical constraint on empirical tests, making large multipopulation comparisons impractical. It may be most practical to compare the predicted and observed fitness consequences of variation in the timing of onset of reproduction.     

Transgenic plants as a source of polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) make a large class of biodegradable biopolymers that are naturally synthesized by numerous microorganisms. These biopolymers could be an alternative to commonly used plastics based on petroleum. Production of PHAs in bioreactors using microorganisms is not widely applied due to its unprofitability. Using transgenic plants for this purpose may be cheaper and more environmental friendly because the biosynthesis of PHAs in plants is based only on water, mineral salts, CO₂ and light. Additionally, plants are not capable of degrading PHAs as bacteria do, and extraction of PHAs from plant tissues is not always necessary. The main objective of this work is a review of possibilities of PHA biosynthesis in transgenic plants and presentation of general information on properties and potential application possibilities of these biopolymers. The possibility of syntheses and accumulation of PHA in several transgenic plants has been studied for some years. Many experiments were performed on model plant Arabidopsis thaliana, however, the research has also revealed a great potential of transgenic crop plants such as camelina (Camelina sativa), tobacco (Nicotiana tabacum) or sugarcane (Saccharum officinarum) as a good sources of PHAs. The highest level of PHAs accumulation in plants was achieved in transgenic A. thaliana (up to 40% of the dry weight of the leaf), and among crop plants in C. sativa (up to 20% of the dry weight of the seed). Increasing knowledge on PHAs permits expansion of the possibilities of these biopolymers use even at a low level of their accumulation in plant tissues.     

Sex allocation in hermaphroditic plants

Hermaphroditic plants allocate their reproductive resources to different functions: male, female and pollinator attraction. While earlier sex-allocation models considered only male and female functions, more recent ones can divide reproductive resources into multiple functions. The basic predictions derived from these models are similar. While most models predict sex allocation at the fruit stage (pollen and seeds), some have examined allocation at the flower stage (pollen and ovules). Selfing rate, mode of pollination and competition among offspring of the same parent are some of the factors that can influence sex allocation among populations. Although the empirical evidence lags behind the theoretical development, sex-allocation theory has been quite successful at predicting trends among populations.     

Sex allocation in heterostylous plants

This paper examines the heterostylous breeding system in plants from the perspective of sex allocation theory. Models are used to predict the frequencies of the different floral morphs in populations of heterostylous species and the relative amounts of resources allocated to pollen and seeds in each morph. We note that in natural populations morph ratios may deviate from equality and that the morphs may specialize in the production of either pollen or seeds. Our sex allocation models are an attempt to explain why such patterns exist.     

Manipulating resource allocation in plants

The distribution of nutrients and assimilates in different organs and tissues is in a constant state of flux throughout the growth and development of a plant. At key stages during the life cycle profound changes occur, and perhaps one of the most critical of these is during seed filling. By restricting the competition for reserves in Arabidopsis plants, the ability to manipulate seed size, seed weight, or seed content has been explored. Removal of secondary inflorescences and lateral branches resulted in a stimulation of elongation of the primary inflorescence and an increase in the distance between siliques. The pruning treatment also led to the development of longer and larger siliques that contained fewer, bigger seeds. This seems to be a consequence of a reduction in the number of ovules that develop and an increase in the fatty acid content of the seeds that mature. The data show that shoot architecture could have a substantial impact on the partitioning of reserves between vegetative and reproductive tissues and could be an important trait for selection in rapid phenotyping screens to optimize crop performance.     

Inherent allocation patterns and potential growth rates of herbaceous climbing plants

We tested the hypothesis that herbaceous climbing plants, unlike non-climbing herbs, maximize height growth and leaf area, with minimal expenditure in support structures. The enhanced investment in leaf area was expected to result in high relative growth rates in terms of biomass increment. Four leguminous herbaceous climbers from nutrient-poor sites and four non-leguminous herbaceous climbers from nutrient-rich sites, were compared with non-climbing, self-supporting leguminous and non-leguminous herbaceous species from similar habitats. Plants were grown in hydroponic cultures in controlled environment chambers. All climbers had inherently taller shoots than self-supporting plants when compared at an equal amount of total plant dry weight, due to longer stems per unit of support biomass. In contrast to the hypothesis, the relative growth rates of all climbers were relatively low compared to the range found for self-supporting species. The biomass allocation patterns of the non-leguminous climbers were similar to those of the self-supporting species. Leguminous climbers allocated more biomass to support tissue and less biomass to leaves than non-climbers. As a result, height growth was even more emphasized in leguminous climbers than in non-leguminous climbers. Climbing legumes had high rates of net carbon gain, which partly compensated the lower relative leaf weight. We conclude that leguminous herbaceous climbers maximize height growth by a large investment in support biomass, enabling them to keep a large proportion of their leaves in the better illuminated environment at the top of the vegetation canopy.     

Transgenic Medicago truncatula plants that accumulate proline display nitrogen-fixing activity with enhanced tolerance to osmotic stress

Legume root nodule nitrogen-fixing activity is severely affected by osmotic stress. Proline accumulation has been shown to induce tolerance to salt stress, and transgenic plants over-expressing Delta(1)-pyrroline-5-carboxylate synthetase (P5CS), which accumulates high levels of proline, display enhanced osmotolerance. Here, we transformed the model legume Medicago truncatula with the P5CS gene from Vigna aconitifolia, and nodule activity was evaluated under osmotic stress in transgenic plants that showed high proline accumulation levels. Nitrogen fixation was significantly less affected by salt treatment compared to wild-type (WT) plants. To our knowledge, this is the first time that transgenic legumes have been produced that display nitrogen-fixing activity with enhanced tolerance to osmotic stress. We studied the expression of M. truncatula proline-related endogenous genes M. truncatulaDelta(1)-pyrroline-5-carboxylate synthetase 1 (MtP5CS1), M. truncatulaDelta(1)-pyrroline-5-carboxylate synthetase 2 (MtP5CS2), M. truncatula ornithine delta-aminotransferase (MtOAT), M. truncatula proline dehydrogenase (MtProDH) and a proline transporter gene in both WT and transgenic plants. Our results indicate that proline metabolism is finely regulated in response to osmotic stress in an organ-specific manner. The transgenic model allowed us to analyse some of the biochemical and molecular mechanisms that are activated in the nodule in response to high salt conditions, and to ascertain the essential role of proline in the maintenance of nitrogen-fixing activity under osmotic stress.     

Photosynthetic capacity and carbon allocation patterns in diverse growth forms of Eucalyptus

Summary Eucalytptus species originating in Australian habitats differing in moisture regimes were examined under uniform growth conditions for their photosynthetic characteristics and allocation patterns. Species from the driest environments, the mallee types, had the smallest leaf sizes and the highest leaf specific weights; and forest species, from moist coastal sites, had the largest and thinnest leaves. Photosynthetic rates on a dry weight basis were highly correlated with leaf nitrogen content in all species. Leaf nitrogen content on a dry weight basis varied little between species in nature; however, there were increasing amounts of nitrogen per unit leaf area as the habitat became drier because of the changes in specific leaf weight. This resulted in a greater light-saturated photosynthetic rate per leaf area of arid habitat species, which were presumably more efficient in water use as a consequence. A simple simulation model showed that changes in the allocation ratio to leaf weight reduces total leaf area in the expected direction without affecting total dry matter accumulation.     

Transgenic maize plants expressing a fungal phytase gene

Maize seeds are the major ingredient of commercial pig and poultry feed. Phosphorus in maize seeds exists predominantly in the form of phytate. Phytate phosphorus is not available to monogastric animals and phosphate supplementation is required for optimal animal growth. Undigested phytate in animal manure is considered a major source of phosphorus pollution to the environment from agricultural production. Microbial phytase produced by fermentation as a feed additive is widely used to manage the nutritional and environmental problems caused by phytate, but the approach is associated with production costs for the enzyme and requirement of special cares in feed processing and diet formulation. An alternative approach would be to produce plant seeds that contain high phytase activities. We have over-expressed Aspergillus niger phyA2 gene in maize seeds using a construct driven by the maize embryo-specific globulin-1 promoter. Low-copy-number transgenic lines with simple integration patterns were identified. Western-blot analysis showed that the maize-expressed phytase protein was smaller than that expressed in yeast, apparently due to different glycosylation. Phytase activity in transgenic maize seeds reached approximately 2,200 units per kg seed, about a 50-fold increase compared to non-transgenic maize seeds. The phytase expression was stable across four generations. The transgenic seeds germinated normally. Our results show that the phytase expression lines can be used for development of new maize hybrids to improve phosphorus availability and reduce the impact of animal production on the environment.     

黑腹果蝇昼夜活动节律及行为时间分配

采用试验室单管观察记录的方法,对3,4,5日龄野生型黑腹果蝇Drosophila melanogaster Meigenw1118成虫每日活动节律进行研究。试验将果蝇活动划分为强活动(飞行和爬行)、弱活动(梳理、觅食等原地发生的运动)和静息(身体不发生移动的休息)3种类型。强活动和弱活动之和为总运动。研究结果显示,野生型黑腹果蝇w1118的昼夜活动表现为明显的双峰模态,晨峰和晚峰分别处于开、关灯前后;雌、雄果蝇总体活动无差异,关灯(18:30)前后雌蝇活动稍强于雄蝇,开灯(6:30)前后则相反;果蝇强活动的节律与总运动基本一致,而弱活动节律不明显;静息节律为单峰模式,其高峰期位于夜间1:00~5:00;雌蝇的静息活动显著多于雄蝇(P<0·05)。     

Neutrophils in cystic fibrosis display a distinct gene expression pattern

We compared gene expression in blood neutrophils (polymorphonuclear leukocytes, or PMNs) collected from healthy subjects with those of cystic fibrosis (CF) patients devoid of bacterial colonization. Macroarray analysis of 1050 genes revealed upregulation of 62 genes and downregulation expression of 27 genes in CF blood PMNs. Among upregulated genes were those coding for vitronectin, some chemokines (particularly CCL17 and CCL18), some interleukin (IL) receptors (IL-3, IL-8, IL-10, IL-12), all three colony-stimulating factors (G-, M-, GM-CSF), numerous genes coding for molecules involved in signal transduction, and a few genes under the control of gamma-interferon. In contrast, none of the genes coding for adhesion molecules were modulated. The upregulation of six genes in CF PMNs (coding for thrombospondin-1, G-CSF, CXCL10, CCL17, IKKvarepsilon, IL-10Ra) was further confirmed by qPCR. In addition, the increased presence of G-CSF, CCL17, and CXCL10 was confirmed by ELISA in supernatants of neutrophils from CF patients. When comparison was performed between blood and airway PMNs of CF patients, there was a limited difference in terms of gene expression. Only the mRNA expression of amphiregulin and tumor necrosis factor (TNF) receptor p55 were significantly higher in airway PMNs. The presence of amphiregulin was confirmed by ELISA in the sputum of CF patients, suggesting for the first time a role of amphiregulin in cystic fibrosis. Altogether, this study clearly demonstrates that blood PMNs from CF patients display a profound modification of gene expression profile associated with the disease, suggesting a state of activation of these cells.     

Transgenic tobacco plants that overexpress alfalfa NADH-glutamate synthase have higher carbon and nitrogen content

This work reports the characterization of transgenic tobacco (Nicotiana tabacum L.) plants that constitutively overexpress NADH-GOGAT. Three independent transformants, designated GOS10, GOS13 and GOS19 (for GOGAT sense), with stable integration of the chimeric alfalfa NADH-GOGAT gene fused to the CaMV 35S promoter were studied. The transgene was stably integrated and inherited by the progeny. In these GOS lines, the expression of NADH-GOGAT mRNA and protein was detected at low levels in roots and leaves, while the expression of the host tobacco NADH-GOGAT gene was nearly undetectable. The roots of GOS lines showed an elevated (15-40%) enzyme activity as compared to control plants. When GOS plants were grown under greenhouse conditions and fed with either nitrate or ammonium as the sole nitrogen source, they showed higher total carbon and nitrogen content in shoots and increased shoot dry weight when plants were entering into the flowering stage, as compared to control plants. The observed phenotype of GOS plants was interpreted as reflecting a higher capacity to assimilate nitrogen due to a higher NADH-GOGAT activity.