N-糖链加工影响里氏木霉形态发生并提高木质纤维素降解能力

[背景] 烟曲霉α-1,2-甘露糖苷酶MsdS在高尔基体中将N-糖链Man₈GlcNAc₂加工为成熟分泌糖蛋白的糖型Man₆GlcNAc₂,有研究表明MsdS与烟曲霉的形态发生、细胞壁合成及蛋白质分泌密切相关;与烟曲霉不同的是,里氏木霉的成熟分泌糖蛋白上的N-糖链结构为Man₈GlcNAc₂,细胞却能正常生长,说明丝状真菌N-糖链的加工具有物种特异性,但其生物学意义不明。[目的] 为研究N-糖链加工对里氏木霉细胞生长及蛋白质分泌的影响,本研究将烟曲霉MsdS转入里氏木霉中以改变其成熟分泌糖蛋白的糖型。[方法] 构建带有烟曲霉msdS基因的重组质粒并转入里氏木霉中,获得msdS表达菌株Tr-MsdS,分析Tr-MsdS菌株的生长表型、N-糖组、蛋白质分泌途径和纤维素酶活性的变化。[结果] 在里氏木霉msdS表达菌株Tr-MsdS中,分泌糖蛋白的主要糖型由出发株的Man₈GlcNAc₂转变为Man₆GlcNAc₂,细胞壁组分发生变化,但细胞壁完整性未受影响;与出发株相比,Tr-MsdS菌株产孢、出芽及分枝增多;另外,MsdS的表达还影响蛋白质分泌,在50℃时降解纤维素和β-葡聚糖的能力分别提高9.9%和32.2%。[结论] 研究结果表明,N-糖链的加工可影响里氏木霉蛋白质,尤其是纤维素酶的分泌,干扰N-糖链加工可能是提高里氏木酶纤维素酶产量的新策略。     

Predictors of Duration and Treatment Failure of Severe Pneumonia in Hospitalized Young Nepalese Children

Background

Pneumonia in young children is still the most frequent cause of death in developing countries. We aimed to identify predictors for recovery and treatment failure in children hospitalized with severe pneumonia.

Methods

We enrolled 610 Nepalese children, aged 2 – 35 months from February 2006 to June 2008. Study participants were provided with standard treatment for pneumonia and followed up until discharge. Three multiple regression models representing clinical variables, clinical and radiological combined and all variables, including C-reactive protein (CRP) and viral etiology were used to assess the associations.

Results

The median age of study participants was 6 months with 493 (82%) infants and 367 (61%) males. The median time (IQR) till recovery was 49 (31, 87) hours and treatment failure was experienced by 209 (35%) of the children. Younger age, hypoxia on admission and radiographic pneumonia were independent predictors for both prolonged recovery and risk of treatment failure. While wasting and presence of any danger sign also predicted slower recovery, Parainfluenza type 1 isolated from the nasopharynx was associated with earlier resolution of illness. Gender, being breastfed, stunting, high fever, elevated CRP, presence of other viruses and supplementation with oral zinc did not show any significant association with these outcomes.

Conclusion

Age, hypoxia and consolidation on chest radiograph were significant predictors for time till recovery and treatment failure in children with severe pneumonia. While chest radiograph is not always needed, detection and treatment of hypoxia is a crucial step to guide the management of hospitalized children with pneumonia.     

Butterfly species diversity and their floral preferences in the Rupa Wetland of Nepal

Floral attributes often influence the foraging choices of nectar‐feeding butterflies, given the close association between plants and these butterfly pollinators. The diversity of butterflies is known to a large extent in Nepal, but little information is available on the feeding habits of butterflies. This study was conducted along the periphery of Rupa Wetland from January to December 2019 to assess butterfly species diversity and to identify the factors influencing their foraging choices. In total, we recorded 1535 individuals of 138 species representing all six families. For our examination of butterfly–nectar plant interactions, we recorded a total of 298 individuals belonging to 31 species of butterfly visiting a total of 28 nectar plant species. Overall, total butterfly visitation was found to be significantly influenced by plant category (herbaceous preferred over woody), floral color (yellow white and purple preferred over pink), and corolla type (tubular preferred over nontubular). Moreover, there was a significant positive correlation between the proboscis length of butterflies and the corolla tube length of flowers. Examining each butterfly family separately revealed that, for four of the families (Lycaenidae, Nymphalidae, Papilionidae, and Pieridae), none of the tested factors (flower color, plant category, and corolla type) were shown to significantly influence butterfly abundance at flowers. However, Hesperidae abundance was found to be significantly influenced by both flower color (with more butterflies observed at yellow flowers than purple) and flower type (with more butterflies observed at tubular flowers than nontubular flowers). Our results reveal that Rupa Lake is a suitable habitat for butterflies, providing valuable floral resources. Hence, further detailed studies encompassing all seasons, a greater variety of plants, and other influential factors in different ecological regions are fundamental for creating favorable environments to sustain important butterfly pollinators and help create balanced wetland ecosystems.     

Multi-locus phylogeographic and population genetic analysis of Anolis carolinensis: historical demography of a genomic model species

The green anole (Anolis carolinensis) has been widely used as an animal model in physiology and neurobiology but has recently emerged as an important genomic model. The recent sequencing of its genome has shed new light on the evolution of vertebrate genomes and on the process that govern species diversification. Surprisingly, the patterns of genetic diversity within natural populations of this widespread and abundant North American lizard remain relatively unknown. In the present study, we use 10 novel nuclear DNA sequence loci (N?=?62 to 152) and one mitochondrial locus (N?=?226) to delimit green anole populations and infer their historical demography. We uncovered four evolutionarily distinct and geographically restricted lineages of green anoles using phylogenetics, bayesian clustering, and genetic distance methods. Molecular dating indicates that these lineages last shared a common ancestor ～2 million years ago. Summary statistics and analysis of the frequency distributions of DNA polymorphisms strongly suggest range-wide expansions in population size. Using Bayesian Skyline Plots, we inferred the timing of population size expansions, which differ across lineages, and found evidence for a relatively recent and rapid westward expansion of green anoles across the Gulf Coastal Plain during the mid-Pleistocene. One surprising result is that the distribution of genetic diversity is not consistent with a latitudinal shift caused by climatic oscillations as is observed for many co-distributed taxa. This suggests that the most recent Pleistocene glacial cycles had a limited impact on the geographic distribution of the green anole at the northern limits of its range.     

Phytophthora aquimorbida sp. nov. and Phytophthora taxon 'aquatilis' recovered from irrigation reservoirs and a stream in Virginia, USA

Two distinct subgroups (L2 and A(-2)) were recovered from irrigation reservoirs and a stream in Virginia, USA. After molecular, morphological and physiological examinations, the L2 subgroup was named Phytophthora aquimorbida and the A(-2) designated as Phytophthora taxon 'aquatilis'. Both taxa are homothallic. P. aquimorbida is characterized by its noncaducous and nonpapillate sporangia, catenulate and radiating hyphal swellings and thick-walled plerotic oospores formed in globose oogonia mostly in the absence of an antheridium. P. taxon 'aquatilis' produces plerotic oospores in globose oogonia mostly with a paragynous antheridium. It has semi-papillate, caducous sporangia with variable pedicels, but it does not have hyphal swelling. Analyses of ITS, CO1, β-tubulin and NADH1 sequences revealed that P. aquimorbida is closely related to P. hydropathica, P. irrigata and P. parsiana, and P. taxon 'aquatilis' is related to P. multivesiculata. The optimum temperature for culture growth is 30 and 20 C for P. aquimorbida and P. taxon 'aquatilis' respectively. Both taxa were pathogenic to rhododendron plants and caused root discoloration, pale leaves, wilting, tip necrosis and dieback. Their plant biosecurity risk also is discussed.     

Extended monitoring of resistance to Bacillus thuringiensis Cry1Ab maize in Diatraea saccharalis (Lepidoptera: Crambidae)

The sugarcane borer, Diatraea saccharalis (F.), is a major target of transgenic maize expressing Bacillus thuringiensis (Bt) proteins in South America and the mid-Southern region of the United States. During 2007-2009, a total of 986 feral individuals of D. saccharalis were collected from maize fields in six locations of Louisiana and Mississippi and examined for resistance to Cry1Ab maize using F 1/F 2 screens. Major resistance alleles to Cry1Ab maize in the populations sampled from non-Bt maize plants during 2007 and 2008 in Louisiana and 2009 in Mississippi were rare. From a total of 487 individuals collected from three locations in Louisiana in 2007 and 2008, only one individual was identified with major resistance alleles. In addition, no major resistance alleles were detected in 242 individuals collected from three locations in Mississippi in 2009. The frequency of major resistance alleles was estimated to be 0.002 with a 95% CI of 0.00025-0.0057 for the Louisiana populations and < 0.0061, with 95% probability, for the Mississippi populations. The resistance frequency estimated for the Louisiana populations in 2007 and 2008 was not significantly different from those reported previously for populations sampled in 2004-2006. However, among 200 individuals sampled from non-Bt maize plants in 2009 in Louisiana, six individuals were identified to possess major resistance alleles. The estimated major resistance allele frequency for the populations sampled from non-Bt maize plants in 2009 in Louisiana was 0.0176 with a 95% CI of 0.0072 to 0.0328, which was significantly greater than those estimated for the populations collected in 2004-2008. Similarly, the frequency of minor resistance alleles to Cry1Ab maize for the Louisiana populations collected in 2009 was also significantly greater than those estimated for the populations sampled before. In addition, two out of 57 feral individuals collected from Bt maize plants in Louisiana in 2009 were identified to carry major resistance alleles to Cry1Ab maize. Since 2010, transgenic maize expressing pyramided Bt genes has been planted in the US mid-Southern region and by 2011, pyramided Bt maize has replaced Cry1Ab maize as the dominant Bt maize for managing lepidopteran pests including D. saccharalis. The timely switching from single-gene Cry1Ab maize to the pyramided Bt maize should prevent further increases in Cry1Ab resistance allele frequency and thus ensure the continued success of Bt maize for managing D. saccharalis in the region.     

Susceptibility of field populations of sugarcane borer from non‐Bt and Bt maize plants to five individual Cry toxins

Abstract Sugarcane borer, Diatraea saccharalis (F.), is a major target of transgenic maize expressing Bacillus thuringiensis (Bt) proteins in South America and the US mid‐south region. Resistance development in target pest populations is a major threat to the sustainable use of Bt crops. In our field trials in 2009, a significant number of live borers and plant injury from D. saccharalis were observed in an experimental SmartStax? maize line. The objective of this study was to assess the relative susceptibility of two field populations of D. saccharalis collected from non‐Bt and Bt maize plants containing SmartStax? traits to five individual Cry proteins. The five Bt proteins included two proteins (Cry1A.105 and Cry2Ab2) that were expressed in SmartStax? maize plants and three other common Bt proteins (Cry1Aa, Cry1Ab and Cry1Ac) that were not produced in SmartStax?. Larval mortality and growth inhibition on Bt diet of the fourth generation after field collections were evaluated 7 days after release of neonates on the diet surface. The laboratory bioassays showed that 50% lethal concentration (LC₅₀) values for Cry1A.105 and Cry2Ab2 for the population originated from Bt plants were 3.55‐ and 1.34‐fold greater, respectively, than those of the population collected from non‐Bt plants. In contrast, relative to the population from non‐Bt plants, the LC₅₀ of the population sampled from Bt plants were 3.85‐, 2.5‐ and 1.64‐fold more sensitive to Cry1Aa, Cry1Ab and Cry1Ac, respectively. The results did not provide clear evidence to conclude that the observed field survival of D. saccharalis on Bt plants was associated with increased levels of resistance.     

Probing the helical tilt and dynamic properties of membrane-bound phospholamban in magnetically aligned bicelles using electron paramagnetic resonance spectroscopy

Wild-type phospholamban (WT-PLB), a Ca(2+)-ATPase (SERCA) regulator in the sarcoplasmic reticulum membrane, was studied using TOAC nitroxide spin labeling, magnetically aligned bicelles, and electron paramagnetic resonance (EPR) spectroscopy to ascertain structural and dynamic information. Different structural domains of PLB (transmembrane segment: positions 42 and 45, loop region: position 20, and cytoplasmic domain: position 10) were probed with rigid TOAC spin labels to extract the transmembrane helical tilt and structural dynamic information, which is crucial for understanding the regulatory function of PLB in modulating Ca(2+)-ATPase activity. Aligned experiments indicate that the transmembrane domain of wild-type PLB has a helical tilt of 13°±4° in DMPC/DHPC bicelles. TOAC spin labels placed on the WT-PLB transmembrane domain showed highly restricted motion with more than 100ns rotational correlation time (τ(c)); whereas the loop, and the cytoplasmic regions each consists of two distinct motional dynamics: one fast component in the sub-nanosecond scale and the other component is slower dynamics in the nanosecond range.