Leaf expansion of four sunflower (Helianthus annuus L) cultivars in relation to water deficits. I. Patterns during plant development

Abstract. The influence of a slow stress and recovery cycle on the pattern of leaf expansion in four diverse sunflower cultivars ( Helianthus annuus L. cvs. Hysun 31, Havasupai, Hopi and Seneca) was studied in a glasshouse. Stress had no significant effect on the time of flower bud emergence and anthesis, or on final leaf number, but delayed the appearance of leaves at high insertions in all cultivars except Hysun 31.
Leaf expansion was markedly reduced as the predawn leaf water potential decreased from −0.35 to −0.60 MPa, and the predawn turgor pressure decreased from 0.3 to 0.2 MPa, and expansion ceased at a predawn leaf water potential of about −1.0 MPa, i.e. when the predawn turgor pressure reached zero.
The leaves most reduced in final size when water was withheld were those at the insertions which grew the most rapidly in unstressed plants. The maximum reduction in final leaf size of 25–35% was similar in all cultivars and was due to retardation of the rate of leaf expansion: the duration of leaf expansion was actually increased by stress. However, leaves that were initiated during stress, but emerged after rewatering, had final leaf areas at least equal to those in the unstressed plants: in the cultivar Seneca, the final size of leaves of high insertion was significantly greater in stressed than unstressed plants, whereas in the three other cultivars the final leaf sizes were similar in both treatments. All four cultivars examined adjusted osmotically to the same degree, but leaf water potentials in one, Seneca, increased more rapidly after rewatering than in the other three, and this may have contributed to the greater relative leaf size in the leaves of high insertion in this cultivar.     

Cytokinins and leaf development in sweet pepper (Capsicum annuum L.)

Stimulation of leaf expansion by an exogenous cytokinin was studied in isolated leaf discs of sweet pepper with emphasis on the assimilate utilization of the tissue. Leaf discs were floated on solutions containing sucrose and plant growth regulators. Benzyladenine (BA) promoted the area expansion rate of the leaf discs. Sucrose at 100 mM resulted in increased area expansion rate compared with 10 mM sucrose. However, the increased sucrose concentration had no influence on the effect of BA. Over a period of 24 h, treatment with BA did not result in any change of sucrose uptake nor of the partitioning of assimilated carbon in the leaf discs. Neither did BA treatment affect the activity of acid invertase (EC 3.2.1.26) or pyrophosphate-dependent phosphofructokinase (EC 2.7.1.90) in the leaf discs. We conclude that the observed promotion of leaf area expansion by exogenous BA is not mediated through the uptake of sucrose or the carbohydrate metabolism of the leaf tissue.Abbreviations BA N⁶-benzyladenine - GA₃ gibberellic acid - PPi-PFK pyrophosphate-dependent phosphofructokinase (EC 2.7.1.90) This study was supported by grants from the Danish Research Counsil (SJVF 13-4148 and 13-4547 to P.U. SJVF 13-4146 and 13-4494 to T.H.N.) and from The Research Center for Plant Biotechnology to P.U.     

Effects of ethylene on the orientation of microtubules and cellulose microfibrils of pea epicotyl cells with polylamellate cell walls

Summary Following a 5 hours ethylene treatment, cortical cells of Pea (Pisum sativum L. var Alaska) epicotyl third internode showed a change in the orientation of both microtubules near the plasma membrane and recently deposited cellulose microfibrils. Control cortical cells had mostly transverse microtubules. The ratio of the average frequency of transverse to longitudinal microtubules was 6.0. After 5 hours of ethylene treatment, cortical cells had mostly longitudinal microtubules, with the ratio of transverse to longitudinal microtubules equal to 0.1. Epidermal cells were more variable than cortical cells with regard to the frequency of longitudinal and transverse microtubules. Observation of cortical cell walls in conventionally stained thin sections revealed that recent deposition of microfibrils had been primarily transverse in almost all of the control cortical cells sampled. In contrast, more than half of the ethylene-treated cortical cells had recent deposition oriented primarily longitudinally. This change in microtubule and microfibril orientation may be early enough to constitute the primary effect of ethylene leading to radial cell expansion.Research supported by NSF grant PCM 78-03244, A1, 2 to PBG and by a Research Corporation grant to WRE.     

Gonadotropin stimulation of steroidogenesis and cellular dispersion in cultured porcine cumuli oophori

The relationship between cellular dispersion and steroidogenesis was studied in culture using oocyte-cumulus complexes harvested from porcine follicles. The cells were cultured in modified TC 199 containing pig serum for one to two days. When oocyte-cumulus complexes were cultured in the absence of hormone the oocytes resumed meiosis, the cumulus cells grew out forming monolayers, and progesterone accumulation was low. Addition of ovine LH, purified human LH, or purified human FSH stimulated expansion of the cumulus mass as well as enhanced progesterone accumulation. Oocyte maturation was not affected by the hormones. In absence of hormone, oocyte-cumulus complexes obtained from large (6–12 mm) follicles showed increased cellular dispersion and higher progesterone accumulation as compared to complexes obtained from medium-sized (3–5 mm) follicles.     

Chromosome-level genome of Tibetan naked carp (Gymnocypris przewalskii) provides insights into Tibetan highland adaptation

Gymnocypris przewalskii, a cyprinid fish endemic to the Qinghai-Tibetan Plateau, has evolved unique morphological, physiological and genetic characteristics to adapt to the highland environment. Herein, we assembled a high-quality G. przewalskii tetraploid genome with a size of 2.03 Gb and scaffold N50 of 44.93 Mb, which was anchored onto 46 chromosomes. The comparative analysis suggested that gene families related to highland adaptation were significantly expanded in G. przewalskii. According to the G. przewalskii genome, we evaluated the phylogenetic relationship of 13 schizothoracine fishes, and inferred that the demographic history of G. przewalskii was strongly associated with geographic and eco-environmental alterations. We noticed that G. przewalskii experienced whole-genome duplication, and genes preserved post duplication were functionally associated with adaptation to high salinity and alkalinity. In conclusion, a chromosome-scale G. przewalskii genome provides an important genomic resource for teleost fish, and will particularly promote our understanding of the molecular evolution and speciation of fish in the highland environment.     

Multiple differentiation centres of a non-Mediterranean butterfly species in south-eastern Europe

Aim  The analysis of the phylogeographical structures of many European species reveals the importance of Mediterranean glacial refugia for many thermophilic species, but also underlines the relevance of extra-Mediterranean glacial differentiation centres for a number of temperate species. In this context, phylogeographical analyses of species from south-eastern Europe are highly important for a comprehensive understanding of Europe as a whole.
Location  Romania and Bulgaria.
Methods  We analysed 19 allozyme loci for 615 individuals of the temperate butterfly species Erebia medusa from 28 populations.
Results  These populations had an intermediate genetic diversity, but the Bulgarian populations were significantly more diverse than the ones north of the Danube in Romania. The differentiation among populations was strong, and 52.1% of the genetic variance among populations was distributed between these two countries. The genetic differentiation was considerably stronger in Romania than in Bulgaria, but several sublineages were distinguished within each of these countries.
Main conclusions  The observed genetic structure is so strong that it is most probably the result of glacial differentiation processes in south-eastern Europe and not a post-glacial structure. The strong differentiation into the two groups north and south of the Danube suggests a separating effect by this river valley. The strong differentiation accompanied with genetic impoverishment in Romania suggests the existence of several differentiation centres: at least two small ones on the southern slopes of the southern Carpathians and one in the eastern Carpathian Basin. The considerably weaker differentiation among the Bulgarian samples and their significantly higher genetic diversity imply that gene flow occurred among different regions of Bulgaria during the last ice age.     

Effects of salt bridges on protein structure and design.

Theoretical calculations (Hendsch ZS & Tidor B, 1994, Protein Sci 3:211-226) and experiments (Waldburger CD et al., 1995, Nat Struct Biol 2:122-128; Wimley WC et al., 1996, Proc Natl Acad Sci USA 93:2985-2990) suggest that hydrophobic interactions are more stabilizing than salt bridges in protein folding. The lack of apparent stability benefit for many salt bridges requires an alternative explanation for their occurrence within proteins. To examine the effect of salt bridges on protein structure and stability in more detail, we have developed an energy function for simple cubic lattice polymers based on continuum electrostatic calculations of a representative selection of salt bridges found in known protein crystal structures. There are only three types of residues in the model, with charges of -1, 0, or + 1. We have exhaustively enumerated conformational space and significant regions of sequence space for three-dimensional cubic lattice polymers of length 16. The results demonstrate that, while the more highly charged sequences are less stable, the loss of stability is accompanied by a substantial reduction in the degeneracy of the lowest-energy state. Moreover, the reduction in degeneracy is greater due to charges that pair than for lone charges that remain relatively exposed to solvent. We have also explored and illustrated the use of ion-pairing strategies for rational structural design using model lattice studies.     

Development of a new bioprocess scheme using frozen seed train intermediates to initiate CHO cell culture manufacturing campaigns

Agility to schedule and execute cell culture manufacturing campaigns quickly in a multi‐product facility will play a key role in meeting the growing demand for therapeutic proteins. In an effort to shorten campaign timelines, maximize plant flexibility and resource utilization, we investigated the initiation of cell culture manufacturing campaigns using CHO cells cryopreserved in large volume bags in place of the seed train process flows that are conventionally used in cell culture manufacturing. This approach, termed FASTEC (Frozen Accelerated Seed Train for Execution of a Campaign), involves cultivating cells to high density in a perfusion bioreactor, and cryopreserving cells in multiple disposable bags. Each run for a manufacturing campaign would then come from a thaw of one or more of these cryopreserved bags. This article reviews the development and optimization of individual steps of the FASTEC bioprocess scheme: scaling up cells to greater than 70 × 10⁶ cells/mL and freezing in bags with an optimized controlled rate freezing protocol and using a customized rack configuration. Flow cytometry analysis was also employed to understand the recovery of CHO cells following cryopreservation. Extensive development data were gathered to ensure that the quantity and quality of the drug manufactured using the FASTEC bioprocess scheme was acceptable compared to the conventional seed train process flow. The result of offering comparable manufacturing options offers flexibility to the cell culture manufacturing network. Biotechnol. Bioeng. 2013; 110: 1376–1385. © 2012 Wiley Periodicals, Inc.     

Increased isolation of two Biosphere Reserves and surrounding protected areas (WAP ecological complex, West Africa)

Protected areas such as nature reserves have been found to be effective in preventing habitat destruction and protecting ecosystems within their borders. Recent studies however found extensive loss of tropical forest habitat around protected areas, vastly contributing to increase the levels of ecological isolation. Using high-resolution satellite data we investigated the isolation trend occurring in the W-Arly-Pendjari (WAP) ecological complex in West Africa. A land-cover change analysis was performed for the period 1984–2002: savanna vegetation extension and loss were derived within the complex and in a 30 km peripheral buffer. Sample regions in the buffer were also analysed using selected spatial indicators to quantify temporal trends in habitat fragmentation. Implications for change in relative capacity to conserve biodiversity were discussed through the calculation of the species richness capacity (SRC). More than 14.5% of savanna habitat was lost in the WAP peripheral areas, while 0.3% was converted inside the complex. The degree of fragmentation of remnant savanna habitat has also drastically increased. Despite the effectiveness of the park conservation programme, we found through the SRC approach that the WAP complex is decreasing its potential capacity to conserve species richness. This process is mainly due to the rapid and extended agricultural expansion taking place around the complex. A better understanding of the ecological dynamics occurring in the peripheral regions of reserves and the consideration of development needs are key variables to achieve conservation goals in protected areas.