Seasonal plasticity of Ludwigia grandiflora under light and water depth gradients: An outdoor mesocosm experiment

Abiotic factors in the introduced area can limit the establishment of exotic species. Adaptation to new abiotic parameters through plastic responses is important for their establishment and distribution pattern. Survival and growth of exotic hydrophytes are related to their plasticity and their ability to adapt to local conditions. Light and water depth are two of the predominant factors determining survival, growth, distribution and abundance of aquatic plants. Although many studies have been carried out on the effect of water level and light on plant performance, their potential interactions are poorly understood. Here, we carried out an outdoor mesocosm experiment, in order to test the role of water depth, light intensity and their potential interactions on the growth and vigour of the invasive macrophyte species Ludwigia grandiflora. Three light intensities (100%, 70% and 50% of sunlight) and three water depths (30, 50 and 80 cm) were tested over a 6-week period, in spring, summer and autumn 2011. We showed that the mortality, biomass, apical and lateral growth of L. grandiflora, as well as its biomass allocation, varied according to the season and responded to both light intensity and water depth. Interactions between water depth and light intensity can have an amplifying effect on the growth of L. grandiflora. Similarities between shade and deep water adaptation responses were observed. A higher biomass and a high morphological plasticity in response to these factors were found particularly at the beginning of the life cycle. Although the invasive amphibious L. grandiflora shows a high tolerance to different water levels and light intensities, the optimal growth conditions for L. grandiflora in our experiment seem to be under full sunlight and in 30 cm of water. Colonization of light or low shade aquatic habitats, as well as shallow environments, can occur due to the high plasticity of L. grandiflora. These results may be important relative to increasing level of water bodies under climatic changes.     

Characterisation of a thermo-alkali-stable lipase from oil-contaminated soil using a metagenomic approach

Lipases are widely used for a variety of biotechnological applications. Screening these industrial enzymes directly from environmental microorganisms is a more efficient and practical approach than conventional cultivation-dependent methods. Combined with activity-based functional screening, six clones with lipase activity were detected and a gene (termed lipZ01) isolated from a target clone with the highest lipase activity was cloned from an oil-contaminated soil-derived metagenomic library and then sequenced. Gene lipZ01 was expressed in Pichia pastoris GS115 and the molecular weight of the recombinant lipase LipZ01 was estimated by electrophoresis analysis to be approximately 50 kDa. The maximum activity of the purified lipase was 42 U/mL, and the optimum reaction temperature and pH value were 45 °C and 8.0, respectively. The enzyme was highly stable in the temperature range 35–60 °C and under alkaline conditions (pH 7–10). The presence of Ca²⁺ and Mn²⁺ ions could significantly enhance the activity of the lipase. The purified lipase preferentially hydrolysed triacylglycerols with acyl chain lengths ≥8 carbon atoms, and the conversion degree of biodiesel production was nearly 92% in a transesterification reaction using olive oil and methanol. Some attractive properties suggested that the recombinant lipase may be valuable in industrial applications.     

Arabidopsis ROP‐interactive CRIB motif‐containing protein 1 (RIC1) positively regulates auxin signalling and negatively regulates abscisic acid (ABA) signalling during root development

Auxin and abscisic acid (ABA) modulate numerous aspects of plant development together, mostly in opposite directions, suggesting that extensive crosstalk occurs between the signalling pathways of the two hormones. However, little is known about the nature of this crosstalk. We demonstrate that ROP‐interactive CRIB motif‐containing protein 1 (RIC1) is involved in the interaction between auxin‐ and ABA‐regulated root growth and lateral root formation. RIC1 expression is highly induced by both hormones, and expressed in the roots of young seedlings. Whereas auxin‐responsive gene induction and the effect of auxin on root growth and lateral root formation were suppressed in the ric1 knockout, ABA‐responsive gene induction and the effect of ABA on seed germination, root growth and lateral root formation were potentiated. Thus, RIC1 positively regulates auxin responses, but negatively regulates ABA responses. Together, our results suggest that RIC1 is a component of the intricate signalling network that underlies auxin and ABA crosstalk.     

Optineurin suppression causes neuronal cell death via NF‐κB pathway

Mutations in more than 10 genes are reported to cause familial amyotrophic lateral sclerosis (ALS). Among these genes, optineurin (OPTN) is virtually the only gene that is considered to cause classical ALS by a loss‐of‐function mutation. Wild‐type optineurin (OPTN^WT) suppresses nuclear factor‐kappa B (NF‐κB) activity, but the ALS‐causing mutant OPTN is unable to suppress NF‐κB activity. Therefore, we knocked down OPTN in neuronal cells and examined the resulting NF‐κB activity and phenotype. First, we confirmed the loss of the endogenous OPTN expression after siRNA treatment and found that NF‐κB activity was increased in OPTN‐knockdown cells. Next, we found that OPTN knockdown caused neuronal cell death. Then, overexpression of OPTN^WT or OPTN^E50K with intact NF‐κB‐suppressive activity, but not overexpression of ALS‐related OPTN mutants, suppressed the neuronal death induced by OPTN knockdown. This neuronal cell death was inhibited by withaferin A, which selectively inhibits NF‐κB activation. Lastly, involvement of the mitochondrial proapoptotic pathway was suggested for neuronal death induced by OPTN knockdown. Taken together, these results indicate that inappropriate NF‐κB activation is the pathogenic mechanism underlying OPTN mutation‐related ALS.

     

Effet du climat et de l’exposition sur la dynamique des populations de la cochenille violette,Parlatoria oleae Colvée (Hemiptera : Diaspididae), en conditions arides

Résumé

Ce travail a pour objectif l’étude de quelques aspects bio-écologiques de la cochenille violette, Parlatoria oleae Colvée 1880, bio-agresseur des cultures de l’Olivier en régions arides. Le suivi du cycle biologique ainsi que la démo-écologie de ce ravageur ont été réalisés grâce à des dénombrements périodiques des populations sur les différents organes de l’arbre (méthodes de Vasseur &; Schvester) de décembre 2010 à décembre 2011 dans la région d’Ain Touta (nord-est algérien). L’espèce y a montré deux générations par an : une génération printanière se développant entre avril et juillet et une génération automnale évoluant entre août et octobre. La ponte débuta en avril et s’échelonna jusqu‘à la fin septembre. L’exposition nord est la plus favorable à cette diaspine qui y trouve des conditions microclimatiques optimales pour son développement. La ponte moyenne est de 8 à 9 ?ufs par femelle. L’analyse statistique de l’effet des conditions climatiques étudiées (températures minimale, maximale et moyenne ; précipitations, gelée et indice d’aridité De Martone) sur les effectifs des différents stades, montre une grande variabilité d’un stade à un autre. L’analyse statistique établie révèle également que les effectifs de l’espèce présentent des variations très hautement significatives selon l’orientation dans l’arbre d’olive colonisé.     

Types and development pathways of lateral line scales in some teleost species

Voronina, E.P. and Hughes, D.R. 2011. Types and development pathways of lateral line scales in some teleost species. —Acta Zoologica (Stockholm) 00 : 1–13. A comparative study of lateral line scales (lls) in nine teleost species was undertaken to trace their ontogenetic structural changes. Three universal characters were used to describe and classify definitive and developing lls. The four main structural types in teleosts are represented. In adult fish, lls are the same structural type in all parts of lateral line in any one specimen, but number of tubules and their orientation may vary. In juvenile fish, except for one species, the structural type of every lls changes with growth, and this process progresses along the lateral line in the direction of development typical for the species. Definitive structural type of the lls is not determined by common scale type and size, presence or absence of nerve foramen on lls, scale overlapping or time of initiation of scales and trunk canal. Development pathways are proposed in which terminal states correspond to the final development of the most complex lls type in Cyprinus carpio, Carassius carassius, Oncorhynchus mykiss, Diplodus annularis and Mullus barbatus. The intermediate states of these pathways correspond to other types of lls as examples of pedomorphosis in Perca fluviatilis, Sander lucioperca, Symphysodon aequifasciatus and Hippoglossoides platessoides.     

A compound CP-31398 suppresses excitotoxicity-induced neurodegeneration

Neurodegeneration causes dysfunction and degeneration of neurons and is triggered by various factors including genetic defects, free radicals, injury, and glutamate excitotoxicity. Among those, glutamate excitotoxicity is implicated in chronic disorders including AD and ALS, and in acute insults in the CNS including traumatic brain injury. Neurological disorders show hallmark morphological abnormalities such as axon degeneration and cell body death. The molecular mechanisms underlying excitotoxicity-induced neurodegeneration are complex and deciphering a molecular mechanism from one angle is beneficial to understand the process, however, still difficult to develop strategies to suppress excitotoxicity-induced degeneration due to existence of other mechanisms. Thus, directly identifying compounds that can modulate excitotoxicity-induced neurodegeneration and subsequently clarifiying the molecular mechanism is a valid approach to develop effective strategies to suppress neurodegeneration. We searched for compounds that can suppress excitotoxicity-induced neurodegeneration and found that CP-31398, a known compound that can rescue the structure and function of the tumor suppressor protein p53 mutant form and stabilize the active conformation of the p53 wild-type form, suppresses excitotoxicity-induced axon degeneration and cell body death. Moreover, CP-31398 suppresses mitochondrial dysfunction which has a strong correlation with excitotoxicity. Thus, our findings identify a compound that can serve as a novel modulator of neurodegeneration induced by glutamate excitotoxicity.     

Sex differences in oxytocin receptor binding in forebrain regions: Correlations with social interest in brain region- and sex- specific ways

Social interest reflects the motivation to approach a conspecific for the assessment of social cues and is measured in rats by the amount of time spent investigating conspecifics. Virgin female rats show lower social interest towards unfamiliar juvenile conspecifics than virgin male rats. We hypothesized that the neuropeptide oxytocin (OT) may modulate sex differences in social interest because of the involvement of OT in pro-social behaviors. We determined whether there are sex differences in OT system parameters in the brain and whether these parameters would correlate with social interest. We also determined whether estrus phase or maternal experience would alter low social interest and whether this would correlate with changes in OT system parameters. Our results show that regardless of estrus phase, females have significantly lower OT receptor (OTR) binding densities than males in the majority of forebrain regions analyzed, including the nucleus accumbens, caudate putamen, lateral septum, bed nucleus of the stria terminalis, medial amygdala, and ventromedial hypothalamus. Interestingly, male social interest correlated positively with OTR binding densities in the medial amygdala, while female social interest correlated negatively with OTR binding densities in the central amygdala. Proestrus/estrus females showed similar social interest to non-estrus females despite increased OTR binding densities in several forebrain areas. Maternal experience had no immediate or long-lasting effects on social interest or OT brain parameters except for higher OTR binding in the medial amygdala in primiparous females. Together, these findings demonstrate that there are robust sex differences in OTR binding densities in multiple forebrain regions of rats and that OTR binding densities correlate with social interest in brain region- and sex-specific ways.     

OsCYP2, a chaperone involved in degradation of auxin‐responsive proteins,plays crucial roles in rice lateral root initiation

Auxin plays a pivotal role in many facets of plant development. It acts by inducing the interaction between auxin‐responsive [auxin (AUX)/indole‐3‐acetic acid (IAA)] proteins and the ubiquitin protein ligase SCF^TIR to promote the degradation of the AUX/IAA proteins. Other cofactors and chaperones that participate in auxin signaling remain to be identified. Here, we characterized rice (Oryza sativa) plants with mutations in a cyclophilin gene (OsCYP2). cyp2 mutants showed defects in auxin responses and exhibited a variety of auxin‐related growth defects in the root. In cyp2 mutants, lateral root initiation was blocked after nuclear migration but before the first anticlinal division of the pericycle cell. Yeast two‐hybrid and in vitro pull‐down results revealed an association between OsCYP2 and the co‐chaperone Suppressor of G2 allele of skp1 (OsSGT1). Luciferase complementation imaging assays further supported this interaction. Similar to previous findings in an Arabidopsis thaliana SGT1 mutant (atsgt1b), degradation of AUX/IAA proteins was retarded in cyp2 mutants treated with exogenous 1‐naphthylacetic acid. Our results suggest that OsCYP2 participates in auxin signal transduction by interacting with OsSGT1.     

独脚金内酯调控植物侧枝发育的分子机制及其与生长素交互作用的研究进展

对独脚金内酯（strigolactones,SLs）调控植物侧枝发育的分子机制及其与生长素相互作用的相关研究结果进行了总结和归纳,在此基础上提出今后的重点研究方向。相关的研究结果显示：在拟南芥[Arabidops~thaliana（Linn．）Heynh．]、豌豆（Pisum sativum Linn．）和水稻（Oryza sativa Linn．）等植物多枝突变体中SLs作为可转导信号参与侧枝发育的分子调控,从这些植物中已克隆获得参与SLs生物合成及信号应答途径的一些基因。作为一种植物激素,SLs在侧枝发育调控网络中与生长素相互作用;腋芽发育与其中生长素的输出密切相关,SLs通过调控芽中生长素的输出间接抑制腋芽发育和侧枝生长,而生长素则在SLs生物合成中起调节作用。