Epoxycarotenoid cleavage by NCED5 fine-tunes ABA accumulation and affects seed dormancy and drought tolerance with other NCED family members

Carotenoid cleavage, catalyzed by the 9-cis-epoxycarotenoid dioxygenase (NCED) constitutes a key step in the regulation of ABA biosynthesis. In Arabidopsis, this enzyme is encoded by five genes. NCED3 has been shown to play a major role in the regulation of ABA synthesis in response to water deficit, whereas NCED6 and NCED9 have been shown to be essential for the ABA production in the embryo and endosperm that imposes dormancy. Reporter gene analysis was carried out to determine the spatiotemporal pattern of NCED5 and NCED9 gene expression. GUS activity from the NCED5 promoter was detected in both the embryo and endosperm of developing seeds with maximal staining after mid-development. NCED9 expression was found at early stages in the testa outer integument layer 1, and after mid-development in epidermal cells of the embryo, but not in the endosperm. In accordance with its temporal- and tissue-specific expression, the phenotypic analysis of nced5 nced6 nced9 triple mutant showed the involvement of the NCED5 gene, together with NCED6 and NCED9, in the induction of seed dormancy. In contrast to nced6 and nced9, however, nced5 mutation did not affect the gibberellin required for germination. In vegetative tissues, combining nced5 and nced3 mutations reduced vegetative growth, increased water loss upon dehydration, and decreased ABA levels under both normal and stressed conditions, as compared with nced3. NCED5 thus contributes, together with NCED3, to ABA production affecting plant growth and water stress tolerance.     

Immobilization to improve the properties of Pseudomonas fluorescens lipase for the kinetic resolution of 3-aryl-3-hydroxy esters

Lipase AK “Amano” 20 from Pseudomonas fluorescens (PFL) was immobilized using diverse immobilization techniques. The methods developed, especially the optimized sol-gel procedure, enabled the fine tuning of enzymatic activity and enantioselectivity for the kinetic resolution of racemic ethyl 3-aryl-3-hydroxypropanoates. The aryl moieties of the racemates include furan-2 and 3-yl, thiophen-2 and 3-yl, benzofuran-2-yl, benzo[b]thiophen-2-yl, as well as phenyl and 4-chloro- and 4-methoxyphenyl groups. The optimized PFL sol-gel preparation (encapsulation from the aqueous solution of PFL, sucrose and Celite in situ) was shown to be efficiently reusable in ten cycles and highly enantioselective with E > 200 to all other substrates except furan-2 and 3-yl and thiophen-2 and 3-yl substituted compounds with E 108-184.     

Chloroplast biogenesis by Arabidopsis seedlings is impaired in the presence of exogenous glucose

Seedlings of Arabidopsis thaliana (L.) Heynh. fail to become green when germinated and grown on media containing high concentrations of glucose (Glc). Although previous studies have shown that sugar concentration affects chlorophyll levels and photosynthetic gene expression, the possibility that sugar concentration might affect actual chloroplast biogenesis has received little attention. Therefore, experiments were conducted to determine whether germination and growth on Glc impairs development of mature chloroplasts from the proplastids found in plant embryos. To monitor chloroplast biogenesis, the levels of a chloroplast-specific fatty acid, hexadecatrienoic (16:3) fatty acid, were measured in Arabidopsis seedlings grown on media containing different concentrations of Glc. These experiments indicate that moderate concentrations of Glc delay accumulation of 16:3. The effects of Glc on 16:3 levels are not solely due to osmotic stress, as equi-molar and even twice equi-molar concentrations of sorbitol do not exert comparable effects. Seedlings grown on concentrations of Glc high enough to prevent greening accumulate almost no 16:3, even after 22 days of growth under continuous light conditions. The lack of 16:3, a major structural component of chloroplast membranes, suggests that seedlings do not develop mature chloroplasts when grown in the presence of high concentrations of exogenous Glc. Further support for this hypothesis is provided by electron microscopy studies revealing that seedlings grown on high concentrations of Glc lack identifiable chloroplasts. Although Glc has been reported to inhibit chloroplast development in unicellular organisms, similar studies on intact higher plants have been lacking.     

Is there a trade‐off between horn growth and survival in adult female chamois?

Life‐history theory predicts trade‐offs in energy allocation between different life‐history traits when resources are limited, i.e. certain traits should be negatively correlated. However, individuals differ in their ability to acquire resources, which can lead to positive correlations between traits at the population level. Here, we investigated the consequences of the allocation in horn growth and body mass on survival in a bovid (Rupicapra rupicapra) with capture‐mark re‐sighting data on 161 females. In female ungulates, body mass often covaries positively with demographic performance and the few studies on horn size suggest that this trait could be a signal of individual quality. Thus, we expected to measure positive correlations between the allocation in these traits and female survival. However, body mass was not correlated to female survival and there was only a negative, though marginal, effect of horn growth. Hence, it seems that the allocation in growth is not an indicator of female quality. Future studies could investigate the importance of growth on female reproduction to evaluate its effect on lifetime reproductive success. Moreover, it is important to confirm in other populations our result that suggests a cost of the allocation in horn growth to better understand the presence of horns in female bovids. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 516–521.     

Soluble ACE2-mediated cell entry of SARS-CoV-2 via interaction with proteins related to the renin-angiotensin system

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The Wiskott-Aldrich syndrome protein directs actin-based motility by stimulating actin nucleation with the Arp2/3 complex.

Actin polymerization at the cell cortex is thought to provide the driving force for aspects of cell-shape change and locomotion. To coordinate cellular movements, the initiation of actin polymerization is tightly regulated, both spatially and temporally. The Wiskott-Aldrich syndrome protein (WASP), encoded by the gene that is mutated in the immunodeficiency disorder Wiskott-Aldrich syndrome [1], has been implicated in the control of actin polymerization in cells [2] [3] [4] [5]. The Arp2/3 complex, an actin-nucleating factor that consists of seven polypeptide subunits [6] [7] [8], was recently shown to physically interact with WASP [9]. We sought to determine whether WASP is a cellular activator of the Arp2/3 complex and found that WASP stimulates the actin nucleation activity of the Arp2/3 complex in vitro. Moreover, WASP-coated microspheres polymerized actin, formed actin tails and exhibited actin-based motility in cell extracts, similar to those behaviors displayed by the pathogenic bacterium Listeria monocytogenes. In extracts depleted of the Arp2/3 complex, WASP-coated microspheres and L. monocytogenes were non-motile and exhibited only residual actin polymerization. These results demonstrate that WASP is sufficient to direct actin-based motility in cell extracts and that this function is mediated by the Arp2/3 complex. WASP interacts with diverse signaling proteins and may therefore function to couple signal transduction pathways to Arp2/3-complex activation and actin polymerization.