Global analysis of plasticity in turgor loss point,a key drought tolerance trait

Many species face increasing drought under climate change. Plasticity has been predicted to strongly influence species' drought responses, but broad patterns in plasticity have not been examined for key drought tolerance traits, including turgor loss or ‘wilting’ point (π_tlp). As soil dries, plants shift π_tlp by accumulating solutes (i.e. ‘osmotic adjustment’). We conducted the first global analysis of plasticity in Δπ_tlp and related traits for 283 wild and crop species in ecosystems worldwide. Δπ_tlp was widely prevalent but moderate (?0.44 MPa), accounting for 16% of post‐drought π_tlp. Thus, pre‐drought π_tlp was a considerably stronger predictor of post‐drought π_tlp across species of wild plants. For cultivars of certain crops Δπ_tlp accounted for major differences in post‐drought π_tlp. Climate was correlated with pre‐ and post‐drought π_tlp, but not Δπ_tlp. Thus, despite the wide prevalence of plasticity, π_tlp measured in one season can reliably characterise most species' constitutive drought tolerances and distributions relative to water supply.     

Effects of photoperiod and temperature on diapause induction in Conogethes punctiferalis （Lepidoptera： Pyralidae）

The yellow peach moth, Conogethes punctiferalis （Guenee）, a multivoltine species that overwinters as diapausing larvae, is one of the most serious insect pests on maize in China. Effect of photoperiod and temperature on larval diapause was examined under empirical laboratory conditions. Short-day treatments caused larval diapause at 25℃, and the critical photoperiod was between 12 and 13 h （or 12 h 51 min） light per day. No sensitive instar was identified for diapause induction under alternated short- （L ： D 11 ： 13 h） and long-day （L ： D 14 ： 10 h） treatments at different larval stages. However, accumulative treatment of three instars and 10 d under short-day treatment was required for the induction of 50% larval diapause. All larvae entered diapause at 20℃, whereas less than 3% did so at 30℃, irrespective of the long- or short-day treatment. Furthermore, under the short-day treatment, more than 90% of larvae went into diapause with temperatures ≤ 25℃, but less than 17% did so at 28℃. In contrast, under the long-day treatment, less than 19% of larvae went into diapause with temperatures ≥23 ℃. The forward shift （5℃） of critical temperature under the long-day regime demonstrated the compensatory effect of temperature and photoperiod on diapause induction. In conclusion, C. punctiferalis had a temperature-dependent type Ⅰ photoperiodic diapause response; there was no sensitive instar for diapause determination, but the photoperiodic accumulation time countermeasures both of the short-day cycles and the number ofinstars exposed, and the photoperiodic diapause response, was a temperature-compensated phenomenon.     

黑河下游胡杨种群的点格局分析

采用空间点格局分析方法中的Ripley K函数,将宏观的地理环境与微观的点格局相结合,分析了不同尺度下黑河下游胡杨种群的空间分布格局.结果表明: 胡杨种群密度随离河距离增大而减小,且东河胡杨种群密度整体上高于西河;胡杨种群分布格局随空间尺度的变化而变化,主要在中尺度5～12 m呈聚集分布,在小尺度0～2 m和大尺度38～40 m呈随机分布,极少呈均匀分布;胡杨种群在不同离河距离主要呈聚集分布,且聚集强度随离河距离的增大呈增大趋势,而胡杨种群在离河距离较远的地段有扩散趋势,转为随机分布.表明胡杨种群内部的生态联系对空间尺度具有很强的依赖性,胡杨种群空间分布主要受表层土壤含水量和地下水埋深的影响.     

大黄素对大鼠离体空肠平滑肌收缩的影响

目的：观察大黄素（emodin）对大鼠离体空肠平滑肌收缩功能的影响,并探讨其作用机制。方法：大鼠离体空肠标本随机分为7组（n=6）：对照组,大黄素剂量组（1,5,10,20μmol／L）,普萘洛尔（PRO）加大黄素组,格列苯脲（GLI）加大黄素组,NG-基-L厂精氨酸甲酯（1．NAME）加大黄素组,无钙K-H液对照组及无钙K-H液大黄素组。采用颈椎离断法处死大鼠并分离其空肠,将肠段标本与张力换能器相连并置于氧饱和的K-H液中。采用BL-420E＋生物信号采集处理系统记录大鼠空肠平滑肌的收缩张力（TE）,幅度（AM）和频率（FR）的影响。结果：①大黄素能使大鼠离体空肠平滑肌的收缩张力和幅度明显下降,且呈剂量依赖性（P〈0．05,P〈0．01）;对频率无明显影响。②普萘洛尔（P〈0．05）、格列苯脲（P〈0．01）可部分阻断大黄素对空肠平滑肌的抑制作用。③L．NAME对大黄素所引起的空肠平滑肌的抑制作用无影响。④氯化钙所引起的空肠平滑肌收缩可被大黄素所抑制（P〈0．01）。结论：大黄素能明显减弱大鼠离体空肠平滑肌的收缩张力和收缩幅度,对收缩频率无影响。这种作用可能是通过兴奋肾上腺素8受体、兴奋ATP敏感钾通道、阻断细胞膜上钙离子通道实现。     

Why minimal is not optimal: Driving the mammalian cell cycle—and drug discovery—with a physiologic CDK control network

Progression through the eukaryotic cell division cycle is governed by the activity of cyclin-dependent kinases (CDKs). For a CDK to become active it must (1) bind a positive regulatory subunit (cyclin) and (2) be phosphorylated on its activation (T) loop. In metazoans, multiple CDK catalytic subunits, each with a distinct set of preferred cyclin partners, regulate the cell cycle, but it has been difficult to assign functions to individual CDKs in vivo. Biochemical analyses and experiments with dominant-negative alleles suggested that specific CDK/cyclin complexes regulate different events, but genetic loss of interphase CDKs (Cdk2, -4 and -6), alone or in combination, did not block proliferation of cells in culture. These knockout and knockdown studies suggested redundancy or plasticity built into the CDK network but did not address whether there was true redundancy in normal cells with a full complement of CDKs. Here, we discuss recent work that took a chemical-genetic approach to reveal that the activity of a genetically non-essential CDK, Cdk2, is required for cell proliferation when normal cyclin pairing is maintained. These results have implications for the systems-level organization of the cell cycle, for regulation of the restriction point and G₁/S transition and for efforts to target Cdk2 therapeutically in human cancers.     

The evolution of multiple mating: Costs and benefits of polyandry to females and of polygyny to males

Polyandry is a paradox: why do females mate multiple times when a single ejaculate often provides enough sperm for lifetime egg production? Gowaty et al. addressed explanations for polyandry in Drosophila pseudoobscura from the perspective of hypotheses based on sex differences in costs of reproduction (CoR). Contrary to CoR, Gowaty et al. showed that (1) a single ejaculate was inadequate for lifetime egg production; (2) polyandry provided fitness benefits to females beyond provision of adequate sperm and (3) fitness benefits of polyandry were not offset by costs. Here, I discuss predictions of the ad hoc hypotheses of CoR and three alternative hypotheses to CoR to facilitate a discussion and further development of a strong inference approach to experiments on the adaptive significance of polyandry for females. Each of the hypotheses makes testable predictions; simultaneous tests of the predictions will provide a strong inference approach to understanding the adaptive significance of multiple mating. I describe a sex-symmetric experiment meant to evaluate variation in fitness among lifelong virgins (V); monogamous females and males with one copulation (M_OC); monogamous females and males with multiple copulations (M_MC); P_AND, polyandrous females; and P_GYN, polygynous males. Last, I recommend the study of many different species, while taking care in choice of study species and attention to the assumptions of specific hypotheses. I particularly urge the study of many more Drosophila species both in laboratory and the wild to understand the “nature of flies in nature,” where opportunities and constraints mold evolutionary responses.     

The enhancement of stability of p53 in MTBP induced p53–MDM2 regulatory network

We have modeled an MTBP-MDM2–p53 regulatory network by integrating p53–MDM2 autoregulatory model (Proctor and Gray, 2008) with the effect of a cellular protein MTBP (MDM2 binding protein) which is allowed to bind with MDM2 (Brady et al., 2005). We study this model to investigate the activation of p53 and MDM2 steady state levels induced by MTBP protein under different stress conditions. Our simulation results in three approaches namely deterministic, Chemical Langevin equation and stochastic simulation of Master equation show a clear transition from damped limit cycle oscillation to fixed point oscillation during a certain time period with constant stress condition in the cell. This transition is the signature of transition of p53 and MDM2 levels from activated state to stabilized steady state levels. We present various phase diagrams to show the transition between unstable and stable states of p53 and MDM2 concentration levels and also their possible relations among critical value of the parameters at which the respective protein level reach stable steady states. In the stochastic approach, the dynamics of the proteins become noise induced process depending on the system size. We found that this noise enhances the stability of the p53 steady state level.     

Effects of acclimation and diapause on the thermal tolerance of the two-spotted spider mite Tetranychus urticae

The two-spotted spider mite, Tetranychus urticae, is a worldwide pest species that overwinters as diapausing females. Cold hardening is presumed to start during diapause development to ensure the successful overwintering of this species. To address this hypothesis, we compared cold tolerance between non-diapausing and diapausing females. We measured supercooling point (SCP) and survival to acute cold stress by exposing the mites at a range of sub-zero temperatures (from −4 to −28 °C for 2 h). The mean SCPs of non-diapausing and diapausing females were −19.6±0.5 and −24.7±0.3 °C respectively, and freezing killed the mites. Diapausing females were significantly more cold tolerant than non-diapausing ones, with LT₅₀ of −19.7 and −13.3 °C, respectively. Further, we also examined the effects of cold acclimation (10 d at 0 or 5 °C) in non-diapausing and diapausing females. Our findings indicated that diapause decreased SCP significantly, while cold acclimation had no effect on the SCP except for non-diapausing females that were acclimated at 5 °C. Acclimation at 5 °C enhanced survival to acute cold stress in diapausing and non-diapausing females, with LT₅₀ of −22.0 and −17.1 °C, respectively. Altogether, our results indicate that T. urticae is a chill tolerant species, and that diapause and cold acclimation elevate cold hardiness in this species.     

Cloning and expression of neuron-specific enolase in the corpus luteum of dairy goats

Neuron-specific enolase (NSE) is the key molecular marker for diffuse neuroendocrine system (DNES) cells, its expression in the pregnant corpus luteum (CL) of dairy goats was studied by the immunofluorescence method and the ultra structural characteristics of luteal cells were detected by the electron microscopy to identify the existence of DNES cells in the pregnant CL of dairy goats. Besides, the coding sequence of dairy goats NSE gene was cloned and its biological information was analyzed. Results revealed that NSE immunopositive cells exhibited widespread cytoplasmic staining throughout the whole pregnant CL. In addition, these cells showed typical characteristics of DNES cells in the electron microscopy. These results suggested that many DNES cells exist in the pregnant CL of dairy goats. Meanwhile, we identified the coding sequence of dairy goats NSE (GenBank Accession No. JN887466). Its nucleotide sequence homology was found to be 97.9%, 89.3%, 90% and 92.6%, respectively, compared with that of Bos taurus, Rattus norvegicus, Mus musculus and Homo sapiens, while the amino acid sequence homology was 99.1%, 97%, 97.2% and 98.2% respectively. These results first showed that the functional amino acids coded by the NSE gene were highly conserved in Caprine, B. taurus, R. norvegicus, M. musculus and H. sapiens. It was implied that the gene NSE in dairy goats had close homology to that of NSE of other species. Our findings demonstrated the possible existence of DNES cells in pregnant CL, providing new clue for further understanding of interactions between the neuroendocrine and reproductive systems. Characterization of gene sequence of dairy goats NSE will enable us to synthesize interference RNA for further study on the role of NSE on the formation, function and apoptosis of pregnant CL in dairy goats.