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991.
CLINTON D. FRANCIS ROBERT P. GURALNICK 《Biological journal of the Linnean Society. Linnean Society of London》2010,101(3):667-679
Divergent adaptive selection is a prominent mechanism influencing patterns of morphological diversity. We used the juniper titmouse [Baeolophus ridgwayi (Richmond, 1902)], a nonmigratory passerine that inhabits woodlands throughout western North America, to investigate variation in bill morphology in relation to diet and geography. We gathered data from museum specimens and used morphometric techniques to determine the relative strength of support for competing hypotheses using information theoretics: (1) differences in bill morphology are predicted by a key winter food resource that each regional population consumes (seeds of different juniper tree species); or (2) bill morphology scales with body size, and both increase along a latitudinal gradient. Juniper species emerged as the variable with the most support explaining variation in bill size, supporting the hypothesis that seed sizes influence bill size, independently of body size. The shape analysis revealed no distinct patterns in bill shape variation, but employed a powerful method for evaluating the strength of support for numerous candidate models. The differences in bill size of juniper titmice across their range are likely to reflect adaptive variation, because bill morphology is highly heritable in birds, juniper titmouse gene flow appears to be relatively low, and there is a clear mechanistic explanation for why bill sizes may differ among the ranges of the three juniper species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 667–679. 相似文献
992.
993.
Transgalactosylated products, 2-O-alpha-D-galactobiosyl-cyclomaltohexaoses (alpha-cyclodextrins, alphaCDs), were synthesized by alpha-galactosidase from coffee bean using melibiose and alphaCD as a donor substrate and an acceptor, respectively. Two positional isomers of 2-O-alpha-galactobiosyl-alphaCDs were isolated and purified by HPLC, and their structures were elucidated by FABMS and NMR spectroscopies, as well as by an enzymatic degradation method. The chromatographic behavior of these novel galactosylated alphaCDs was compared on three HPLC columns with different separation modes. 相似文献
994.
红根甘肃桃根系MYB基因片段的克隆及序列分析 总被引:2,自引:0,他引:2
为了明确MYB转录因子在红根甘肃桃抗性分子机制中的作用.通过RT-PCR从红根甘肃桃根系cDNA中克隆了14个MYB基因片段,序列分析表明这些片段与苹果、葡萄、拟南芥、番茄等植物的MYB转录因子高度同源;系统进化分析显示红根甘肃桃的11个PkMYB分别与拟南芥、番茄、杨树、柿等植物中已知功能的MYB转录因子聚在不同的亚类,据此推测它们可能有相似的功能.试验结果为进一步研究MYB基因在红根甘肃桃抗性机制中的作用奠定了基础. 相似文献
995.
996.
Mouse intestinal bacteria (MIB) is a new operational taxonomic unit (OTU) belonging to the Bacteroides subgroup in the Cytophaga-Flavobacter-Bacteroides (CFB) phylum recently found in the intestine of mice, rats and humans. However, their characters are still unknown since they have not yet been isolated by culture. To understand their habitat characteristics in intestinal tracts, the quantification assays of MIB were established using MIB group-specific primers. The MIB population in the intestine was evaluated as a percentage of the number of 16S rRNA gene copy of MIB. A real-time PCR assay using group specific primers showed the fluctuation of MIB inhabitancy and revealed that the MIB population in the small intestine of mice was significantly lower than the large intestinal contents. Moreover, MIB was found in human feces though the number was lower than in murine. This assay using group-specific primers revealed new information about host-preference of MIB. 相似文献
997.
Receptor‐like kinase OsSIK1 improves drought and salt stress tolerance in rice (Oryza sativa) plants
Shou‐Qiang Ouyang Yun‐Feng Liu Peng Liu Gang Lei Si‐Jie He Biao Ma Wan‐Ke Zhang Jin‐Song Zhang Shou‐Yi Chen 《The Plant journal : for cell and molecular biology》2010,62(2):316-329
Receptor‐like kinases (RLKs) play essential roles in plant growth, development and responses to environmental stresses. A putative RLK gene, OsSIK1, with extracellular leucine‐rich repeats was cloned and characterized in rice (Oryza sativa). OsSIK1 exhibits kinase activity in the presence of Mn2+, and the OsSIK1 kinase domain has the ability to autophosphorylate and phosphorylate myelin basic protein (MBP). OsSIK1 promoter‐GUS analysis revealed that OsSIK1 is expressed mainly in the stem and spikelet in rice. The expression of OsSIK1 is mainly induced by salt, drought and H2O2 treatments. Transgenic rice plants with overexpression of OsSIK1 show higher tolerance to salt and drought stresses than control plants. On the contrary, the knock‐out mutants sik1‐1 and sik1‐2, as well as RNA interference (RNAi) plants, are sensitive to drought and salt stresses. The activities of peroxidase, superoxide dismutase and catalase are enhanced significantly in OsSIK1‐overexpressing plants. Also, the accumulation of H2O2 in leaves of OsSIK1‐overexpressing plants is much less than that of the mutants, RNAi plants and control plants, as measured by 3,3′‐diamino benzidine (DAB) staining. We also show that OsSIK1 affects stomatal density in the abaxial and adaxial leaf epidermis of rice. These results indicate that OsSIK1 plays important roles in salt and drought stress tolerance in rice, through the activation of the antioxidative system. 相似文献
998.
999.
Xin‐Hua Ma Zhi‐Biao Wang Lei Zhang Wei Li Cui‐Min Deng Tian‐Hua Zhong Guang‐Yu Li Wei‐Ming Zheng Yong‐Hong Zhang 《化学与生物多样性》2017,14(5)
One new ent‐kaurane diterpenoid, 11β,16α‐dihydroxy‐ent‐kauran‐19‐oic acid ( 1 ), together with eight known analogues 2 – 9 were isolated from the aerial parts of Wedelia prostrata. One of the acidic diterpenoids, kaurenoic acid ( 3 ), was converted to seven derivatives, 10 – 16 . All compounds were evaluated for their cytotoxic activity in vitro against human leukemia (K562), liver (HepG‐2), and stomach (SGC‐7901) cancer cell lines. Only four kaurenoic acid derivatives, 13 – 16 , with 15‐keto and substitutions at C(19) position, exhibited notable cytotoxic activities on these tumor cell lines with IC50 value ranging from 0.05 to 3.71 μm . Compounds 10 – 12 , with oxime on C(15) showed moderate inhibitory effects and compounds 1 – 9 showed no cytotoxicities on them. Structure–activity relationships were also discussed based on the experimental data obtained. The known derivative, 15‐oxokaurenoic acid 4‐piperdin‐1‐ylbutyl ester ( 17 ), induced typical apoptotic cell death in colon SW480 cells upon evaluation of the apoptosis‐inducing activity by flow‐cytometric analysis. 相似文献
1000.
Host discrimination modulates brood guarding behaviour and the adaptive superparasitism in the parasitoid wasp Trissolcus semistriatus (Hymenoptera: Scelionidae) 下载免费PDF全文
Because hosts utilized by parasitoids are vulnerable to further oviposition by conspecifics, host guarding benefits female wasps. The present study aims to test whether female adults regulate brood guarding behaviour by host discrimination in a solitary parasitoid Trissolcus semistriatus by presenting an intact or parasitized host egg mass to a female adult. Virgin females without oviposition experience have host discrimination ability, which enables them to adjust the number of eggs laid in the hosts. Mating experience increases superparasitism by female adults, whereas mated females achieve a higher discrimination ability as a result of oviposition experience and show a lower superparasitism rate. As expected, females exhibit brood guard after parasitizing an intact host egg mass, whereas those females visiting a previously parasitized host egg mass, do not. Because the survival of eggs in superparasitized hosts is relatively low, regulating brood guarding behaviour by host discrimination is adaptive for female wasps. 相似文献