临泽绿洲边缘区棉花群体光合速率、蒸腾速率及水分利用效率

在甘肃河西走廊中部黑河中游绿洲边缘区,于6月下旬和8月上旬,利用Li-8100土壤碳通量测定系统与改进的同化箱联合对田间条件下早熟陆地棉(Gossypium hirsutum)品种新陆早8号的群体光合特性进行了研究.结果表明：试验地6月下旬的土壤呼吸速率和土壤蒸发速率显著高于8月上旬（P＜0.01）;棉花群体光合速率日变化均呈“单峰型”,6月下旬的群体光合速率显著高于8月上旬,其日平均值分别为（43.11±1.26）和（24.53±0.60）μmol CO₂·m^-2·s^-1, 差异极显著（P＜0.01）;群体蒸腾速率日变化也呈“单峰型”,6月下旬和8月上旬的日平均值分别为（3.10±0.34）和（1.60±0.26）mmol H₂O·m^-2·s^-1,两者存在极显著差异（P＜0.01）;6月下旬和8月上旬的群体水分利用效率日平均值分别为（15.67±1.77）和（23.08±5.54） mmol CO₂·mol^-1 H₂O,但差异不显著（P＞0.05）.两生育时期棉花群体光合速率与温度、光合有效辐射及土壤含水量均呈正相关关系.表明棉花群体光合速率在6月下旬和8月上旬均没有出现中午光合下调,8月由于土壤水分降低和植物叶片衰老,棉花群体光合速率和蒸腾速率显著降低,但水分利用效率并无显著下降.     

The effect of the armored scale,Rhizaspidiotus donacis (Hemiptera: Diaspididae), on shoot growth of the invasive plant Arundo donax (Poaceae: Arundinoideae)

The effect of feeding by the armored scale, Rhizaspidiotus donacis (Leonardi, 1920) (Hemiptera: Diaspididae) on the growth of the plant Arundo donax L. (Poaceae) was evaluated under field conditions in its native range. The study was designed to evaluate the impact of R. donacis, a candidate agent for biological control of A. donax which is invasive in arid riparian ecosystems of the Southwestern USA and Mexico. The study was carried out at five A. donax sites in the Province of Alicante, Spain, differing in altitude and climate. At each site, 30 infested lateral shoots were selected and 15 were randomly treated monthly with imidacloprid insecticide. Shoot lengths were measured monthly over a 1-year period in a comparative growth analysis. Shoots infested with R. donacis had an over 2-fold reduced growth rate as compared to treated shoots. Growth of shoots varied by site, and the effect of R. donacis on growth was most pronounced in the late spring, when mature females produced first instar scale crawlers. The impact of R. donacis on A. donax growth under field conditions in the native range, combined with its narrow host specificity, indicate that R. donacis is a promising candidate for biological control of A. donax in North America and other areas invaded by this weed.     

Thermal biology of African lovebirds and Australian grass parakeets

We compared aspects of the thermal biology of two groups of small parrots, of similar body mass, each derived from a range of habitat types, varying in aridity, but indigenous to either southern Africa or Australia. By accounting for phylogenetic differences, we were able to question whether arid zone species have lower metabolic rates and greater thermal tolerances than mesic species in relation to the “pre-adapted” and “post-arrival adaptation” hypotheses. Four species of African lovebird (Agapornis) and four species of Australian grass parakeet (one Neopsephotus and three Neophema species) were investigated. The Rosy-faced Lovebird (Agapornis roseicollis), Bourke's Parakeet (Neopsephotus bourkii) and the Scarlet-chested Parakeet (Neophema splendida) were categorised as arid zone species, Fischer's Lovebird (Agapornis fischeri), the Black-masked Lovebird (Agapornis personatus) and the Elegant Parakeet (Neophema elegans) as semi-arid zone species, and the Black-cheeked Lovebird (Agapornis nigrigenis) and the Turquoise Parakeet (Neophema pulchella) as mesic zone species. Conventional and phylogenetically independent statistical methods yielded no significant differences in the basal metabolic rates of birds from different habitats or between the species assemblages from Africa and Australia.     

Quantitative Metaproteomics and Activity-based Protein Profiling of Patient Fecal Microbiome Identifies Host and Microbial Serine-type Endopeptidase Activity Associated With Ulcerative Colitis

The gut microbiota plays an important yet incompletely understood role in the induction and propagation of ulcerative colitis (UC). Organism-level efforts to identify UC-associated microbes have revealed the importance of community structure, but less is known about the molecular effectors of disease. We performed 16S rRNA gene sequencing in parallel with label-free data-dependent LC-MS/MS proteomics to characterize the stool microbiomes of healthy (n = 8) and UC (n = 10) patients. Comparisons of taxonomic composition between techniques revealed major differences in community structure partially attributable to the additional detection of host, fungal, viral, and food peptides by metaproteomics. Differential expression analysis of metaproteomic data identified 176 significantly enriched protein groups between healthy and UC patients. Gene ontology analysis revealed several enriched functions with serine-type endopeptidase activity overrepresented in UC patients. Using a biotinylated fluorophosphonate probe and streptavidin-based enrichment, we show that serine endopeptidases are active in patient fecal samples and that additional putative serine hydrolases are detectable by this approach compared with unenriched profiling. Finally, as metaproteomic databases expand, they are expected to asymptotically approach completeness. Using ComPIL and de novo peptide sequencing, we estimate the size of the probable peptide space unidentified (“dark peptidome”) by our large database approach to establish a rough benchmark for database sufficiency. Despite high variability inherent in patient samples, our analysis yielded a catalog of differentially enriched proteins between healthy and UC fecal proteomes. This catalog provides a clinically relevant jumping-off point for further molecular-level studies aimed at identifying the microbial underpinnings of UC.     

Impact of the zebra mussel Dreissena polymorpha invasion on the budget of suspended material in a shallow lagoon ecosystem

The role of the zebra mussel Dreissena polymorpha in redistribution of total particulate material (TPM) between the water column and bottom sediment was estimated using the TPM budget for a mussel bed in the Curonian lagoon, the Baltic Sea. Seasonal clearance rates were derived from the TPM budget assuming two resuspension scenarios: no resuspension and full resuspension of biodeposits. Estimated clearance rates for both scenarios were compared with the rates calculated from the population clearance rate model. Seasonal clearance rates estimated using the population model (1.1 and 11.8 l g⁻¹ SFDW day⁻¹) fitted well into the interval of seasonal clearance rates calculated from TPM budgets assuming no resuspension of biodeposits (3.2 and 21.4 l g SFDW⁻¹ day⁻¹). In the scenario with biodeposits resuspension clearance rates were much higher (57.4 and 148.9 g SFDW⁻¹ day⁻¹). The ratio of clearance to residence time was highly dependent on the fate of biodeposits. Therefore its use in interpretation of the species impact on TPM was limited. An alternative measure based on the ratio of the amount of TPM biodeposited to TPM transported into the bed was used. It was found that zebra mussels are able to deposit between 10 and 30% of the incoming TPM, and the amount of biodeposited material was correlated with water residence time. Results indicate that the impact of zebra mussels on TPM in the lagoon is small relative to the high transport rates of TPM over the bed. However, annual biosedimentation rate (~590 g m⁻²) in the mussel bed was higher than physical deposition rate (~380 g m⁻²) in accumulation areas devoid of large suspension feeders. We suggest that a local impact due to enhanced availability of organic material to other trophic groups of associated benthic organisms may be more significant than effects on TPM pathways at an ecosystem scale.     

Cell Size and Growth Rate Are Modulated by TORC2-Dependent Signals

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Identifying differentially expressed genes in meta-analysis via Bayesian model-based clustering

A Bayesian model-based clustering approach is proposed for identifying differentially expressed genes in meta-analysis. A Bayesian hierarchical model is used as a scientific tool for combining information from different studies, and a mixture prior is used to separate differentially expressed genes from non-differentially expressed genes. Posterior estimation of the parameters and missing observations are done by using a simple Markov chain Monte Carlo method. From the estimated mixture model, useful measure of significance of a test such as the Bayesian false discovery rate (FDR), the local FDR (Efron et al., 2001), and the integration-driven discovery rate (IDR; Choi et al., 2003) can be easily computed. The model-based approach is also compared with commonly used permutation methods, and it is shown that the model-based approach is superior to the permutation methods when there are excessive under-expressed genes compared to over-expressed genes or vice versa. The proposed method is applied to four publicly available prostate cancer gene expression data sets and simulated data sets.