Variation in sporophytic and gametophytic vigor in wild and cultivated varieties of Cucurbita pepo and their F1 and F2 generations

 This study examines sporophytic and gametophytic vigor in wild and cultivated varieties of Cucurbita pepo L. and their hybrids in order to determine whether hybrid vigor extends to the microgametophyte generation. It also examines the variation in sporophytic and gametophytic vigor to discern the non-genetic influences of pollen provisioning by the sporophyte on pollen performance from the genetic influences of the microgametophyte’s own genotype on pollen performance. A cultivated and a wild C. pepo and their F1 and the F2 generations were grown under field conditions and flower and fruit production were monitored over one summer. We found that the four types of plants differed significantly in the number of male and female flowers and the number of fruits they produced. The F1 plants produced significantly more male flowers and marginally more female flowers and fruits than the parental lines. To estimate gametophytic vigor pollen was germinated in vitro and pollen tube length measured after 30 min. We found that pollen tubes from the F1 plants had significantly greater growth than tubes from the parental lines or the F2 generation, indicating that hybrid vigor extends to the microgametophytic generation. By partitioning the variance of pollen tube growth into ’within’ and ’among’ plant components of variation, we were able to show that the genotype of the microgametophyte influences pollen performance in vitro, but that expression of hybrid vigor in the microgametophyte is likely to be due to an environmental effect related to provisioning of the pollen grains during development. Received: 16 April 1998 / Revision accepted: 18 August 1998     

Isolation and purification of proteins from the symbiosome membrane of yellow lupine root nodules

A unique feature of the symbiotic association between legume plants and rhizobia is the plant-derived membrane which separates the symbionts within root nodule; this membrane is termed the peribacteroid membrane (PBM). Although this membrane plays a vital role in facilitating transport and other processes in nodules, little is known about the proteins that are associated with and are an integral part of it. The objective of this work was to apply modern methods of protein purification to the characterisation of proteins of peribacteroid membrane from nodules of yellow lupine (Lupines luteus). The 17-kDa protein was isolated from purified peribacteroid membrane using size exclusion and ion exchange chromatography (FPLC). The N-terminal amino acid sequence of this protein was determined; the sequence does not match any of the previously reported lupine and other legume sequences. Following detergent solubilisation of purified peribacteroid membrane, integral proteins of 15 to 20 kDa were purified by size exclusion chromatography.     

重组大肠杆菌YK537/pSB┐TK高密度培养过程中有机酸的RP┐HPLC快速分析

采用高压液相色谱法（ＨＰＬＣ）,利用Ｃ１８反相柱快速检测重组大肠杆菌ＹＫ５３７／ｐＳＢ－ＴＫ高密度发酵过程中细菌代谢产生的各种有机酸。分析表明,经乙醚和水两次萃取处理后能去除样品中大部分的干扰峰,可获得理想的分离效果,并能定量测出发酵过程中各种有机酸的积累。不同培养方式的结果表明用甘油代替葡萄糖作为细菌生长的碳源可减少乙酸的积累,降低其对细菌生长和外源蛋白表达的抑制作用,从而更易实现重组大肠杆菌的高表达、高密度培养。     

Mating competition and intergroup transfer of males in Tibetan macaques (Macaca thibetana) at Mt. Emei,China

In five groups of seasonally provisioned Tibetan macaques (Macaca thibetana) at Mt. Emei, males were sampled for wounds as an indicator of their competition for females during about 80 days in the 1987 mating season. Quantitative data on intergroup transfer were collected in a period between June 1986 and December 1987. The young adult (YA) males, the most active age-class in mating activity and intergroup transfer, received most of the wounds. Wounds tended to appear more in the front of body for YA and subadults (SA) than they did for middle-old aged (MO) males. This implies that some of the MO males were more active and aggressive in the fights. During the 1.5 year period, 5/6 of the YA and 5/17 of the MO males made intergroup shifts. Although YA males faced a high risk of receiving wounds at transfer, they usually rose in rank. On the other hand, the MO males transferred more smoothly but dropped in rank. The peripheral SA males, which rarely emigrated in the population, were an active component in determining the wounding rate, and the rate and direction of male migration. Three SA immigrants died of severe attacks made by resident males in 1988 and 1991. Adult sex ratios and their variations were considerably reduced with male nonrandom shifts and better conservation of the population.     

Analytical and micropreparative peptide mapping by high performance liquid chromatography/electrospray mass spectrometry of proteins purified by gel electrophoresis.

We report the use of microbore reverse-phase high performance liquid chromatography connected on-line to an electrospray mass spectrometer for the separation/detection of peptides derived by proteolytic digestion of proteins separated by polyacrylamide gel electrophoresis. A small fraction (typically 10% of the total) of the peptides eluting from the column was diverted through a flow-splitting device into the ion source of the mass spectrometer, whereas the majority of the peptide samples was collected for further analyses. We demonstrate the feasibility of obtaining reproducible peptide maps from submicrogram amounts of protein applied to the gel and good correlation of the signal detected by the mass spectrometer with peptide detection by UV absorbance. Furthermore, independently verifiable peptide masses were determined from subpicomole amounts of peptides directed into the mass spectrometer. The method was used to analyze the 265-kDa and the 280-kDa isoforms of the enzyme acetyl-CoA carboxylase isolated from rat liver. The results provide compelling evidence that the two enzyme isoforms are translation products of different genes and suggest that these approaches may be of general utility in the definitive comparison of protein isoforms. We furthermore illustrate that knowledge of peptide masses as determined by this technique provides a major advantage for error-free data interpretation in chemical high-sensitivity peptide sequence analysis.     

A pilot study investigating motor adaptations when learning to walk with a whole-body powered exoskeleton

Evidence is emerging on how whole-body powered exoskeleton (EXO) use impacts users in basic occupational work scenarios, yet our understanding of how users learn to use this complex technology is limited. We explored how novice users adapted to using an EXO during gait. Six novices and five experienced users completed the study. Novices completed an initial training/familiarization gait session, followed by three subsequent gait sessions using the EXO, while experienced users completed one gait session with the EXO. Spatiotemporal gait measures, pelvis and lower limb joint kinematics, muscle activities, EXO torques, and human-EXO interaction forces were measured. Adaptations among novices were most pronounced in spatiotemporal gait measures, followed by joint kinematics, with smaller changes evident in muscle activity and EXO joint torques. Compared to the experienced users, novices exhibited a shorter step length and walked with significantly greater anterior pelvic tilt and less hip extension. Novices also used lower joint torques from the EXO at the hip and knee, and they had greater biceps femoris activity. Overall, our results may suggest that novices exhibited clear progress in learning, but they had not yet adopted motor strategies similar to those of experienced users after the three sessions. We suggest potential future directions to enhance motor adaptations to powered EXO in terms of both training protocols and human-EXO interfaces.     

Plastic value chain and performance metric framework for optimal recycling

Despite the promotion of plastic recycling to sustainably manage plastic waste and advance the circular economy, existing plastic recycling systems globally are largely experiencing low performance and growth. To transition to world-class plastic material recycling and circularity, defining the metrics that impact the performance of a plastic recycling system is crucial. Bringing together existing literature, this study developed a conceptual framework, comprised of eight key performance metrics, for benchmarking recycling success or assessing the degree to which the performance of any plastic recycling system is optimal. Through a value chain approach, the specific performance metrics relevant to each stage of the plastic recycling system, their objectives, and the actors characterizing the system were analyzed in detail. Also, specific maturity models were developed to measure the performance of any plastic recycling system. This framework provides essential knowledge for related stakeholders to inform further development of plastic recycling and a circular economy.     

Widespread latitudinal asymmetry in the performance of marginal populations: A meta-analysis

Aim

Range shifts are expected to occur when populations at one range margin perform better than those at the other margin, yet no global trend in population performances at range margins has been demonstrated empirically across a wide range of taxa and biomes. Here we test the prediction that, if impacts of ongoing climate change on performance in marginal populations are widespread, then populations from the high-latitude margin (HLM) should perform as well as or better than central populations, whereas low-latitude margin (LLM) populations should perform worse.

Location

Global.

Time period

1995–2019.

Major taxa studied

Plants and animals.

Methods

To test our prediction, we used a meta-analysis to quantify empirical support for asymmetry in the performance of high- and low-latitude margin populations compared to central populations. Performance estimates (survival, reproduction, or lifetime fitness) for populations occurring in their natural environment were derived from 51 papers involving 113 margin-centre comparisons from 54 species and 705 populations from the Americas, Europe, Africa and Australia. We then related these performance differences to climatic differences among populations. We also tested whether patterns are consistent across taxonomic kingdoms (plants vs animals) and across realms (marine vs terrestrial).

Results

Populations at margins performed significantly worse than central populations, and this trend was primarily driven by the low-latitude margin. Although the difference was of small magnitude, it was largely consistent across biological kingdoms and realms. Differences in performance were weakly (p = .08) related to the difference in average temperatures between central and marginal populations.

Main conclusions

The observed asymmetry in performance in marginal populations is consistent with predictions about the effects of global climate change, though further research is needed to confirm the effect of climate. It indicates that changes in demographic rates in marginal populations can serve as early-warning signals of impending range shifts.     

Pollen as the link between floral phenotype and fitness

Pollen plays a key role in plant reproductive biology. Despite the long history of research on pollen and pollination, recent advances in pollen-tracking methods and statistical approaches to linking plant phenotype, pollination performance, and reproductive fitness yield a steady flow of exciting new insights. In this introduction to the Special Issue “Pollen as the Link Between Phenotype and Fitness,” we start by describing a general conceptual model linking functional classes of floral phenotypic traits to pollination-related performance metrics and reproductive fitness. We use this model as a framework for synthesizing the relevant literature, highlighting the studies included in the Special Issue, and identifying gaps in our understanding and opportunities for further development of the field. The papers that follow in this Special Issue provide new insights into the relationships between pollen production, presentation, flower morphology, and pollination performance (e.g., pollen deposition onto stigmas), the role of pollinators in pollen transfer, and the consequences of heterospecific pollen deposition. Several of the studies demonstrate exciting experimental and analytical approaches that should pave the way for continued work addressing the intriguing role of pollen in linking plant phenotypes to reproductive fitness.     

High performance liquid chromatography of biliprotein from Bangia atropurpurea ‘Conchocelis’

Gel-filtration-purified R-phycoerythrin and phycocyanin from the filamentous phase of Bangia atropurpurea were subjected to high performance anion exchange chromatographic separation. The purified R-phycoerythrin was a mixture of three charged-isomers that were well resolved in a Bio-Gel MA7P column by elution with a NaCl gradient in phosphate buffer. These were tentatively called phycoerythrin charged-isomers and were also separable from phycocyanin and allophycocyanin by the same system. Hence, it is suggested that the ion exchange chromatographic and the sample preparation methods presented in this report can be used to distinguish the various natures of biliproteins in red algae in addition to the polyacrylamide gel electrophoresis technique. Isomers of R-phycoerythrin have the same absorption and emission spectra and were studied for their subunit compositions by a PRP-3 reverse phase column chromatography. All three charged-isomers have the same and subunits in common but differ in their subunit.