MHC class II DR classification based on antigen-binding groove natural selection

Major histocompatibility complex (MHC) genes are highly polymorphic and play key roles in immune susceptibility and resistance to pathogens. While the immunological and structural functions of several human and murine alleles have been analyzed, little is known about the MHC molecules of other animals. Here, we could classify five mammalian species into three groups (human, cow and dog, and cat and pig) on the basis of DRB nucleotide sequences, synonymous and nonsynonymous mutation rates, and natural selection of individual residues. These observations, along with the locations of the positively and negatively selected residues in three-dimensional DR structures, suggest that the antigen-recognition sites of swine and feline DR molecules have been negatively selected while those of bovine and canine DR molecules have been positively selected. Human DR molecules show evidence of high negative and positive selection. Our observations suggest that MHC-DR molecules are under different selective force depending on each species.     

Functional analyses of the ABI1-related protein phosphatase type 2C reveal evolutionarily conserved regulation of abscisic acid signaling between Arabidopsis and the moss <Emphasis Type="Italic">Physcomitrella patens</Emphasis>

We employed a comparative genomic approach to understand protein phosphatase 2C (PP2C)-mediated abscisic acid (ABA) signaling in the moss Physcomitrella patens. Ectopic expression of Arabidopsis (Arabidopsis thaliana) abi1-1, a dominant mutant allele of ABI1 encoding a PP2C involved in the negative regulation of ABA signaling, caused ABA insensitivity of P. patens both in gene expression of late embryogenesis abundant (LEA) genes and in ABA-induced protonemal growth inhibition. The transgenic abi1-1 plants showed decreased ABA-induced freezing tolerance, and decreased tolerance to osmotic stress. Analyses of the P. patens genome revealed that only two (PpABI1A and PpABI1B) PP2C genes were related to ABI1. In the ppabi1a null mutants, ABA-induced expression of LEA genes was elevated, and protonemal growth was inhibited with lower ABA concentration compared to the wild type. Moreover, ABA-induced freezing tolerance of the ppabi1a mutants was markedly enhanced. We provide the genetic evidence that PP2C-mediated ABA signaling is evolutionarily conserved between Arabidopsis and P. patens. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Accession Numbers: PpABI1A-AB369256, PpABI1B-AB369255, pphn39k21-AB369257.     

介绍拍摄几种植物运动的方法

介绍用显微摄影装置定格拍摄气孔开闭、颖花开闭、浆片膨大、花粉萌发,用扫描仪录入稻穗开花以及用相机拍摄稻根负向光性生长等植物运动的技术和方法,并展示所摄植物运动的照片。     

Controlled Gating of Lysenin Pores

Lysenin forms unitary large conductance pores in artificial bilayer membranes containing sphingomyelin. A population of lysenin pores inserted into such a bilayer membrane exhibited a dynamic negative conductance region, as predicted by a simple two-state model for voltage-gated channels. The recorded I-V curves demonstrated that lysenin pores inserted into the bilayer are uniformly oriented. Additionally, the transition between the two-states was affected by changes in the monovalent ion concentration and pH, pointing towards an electrostatic interaction governing the gating mechanism.     

Operant generalization in quail neonates after intradimensional training: Distinguishing positive and negative reinforcement

Operant generalization has been demonstrated in neonates only recently. To investigate the development of intradimensional stimulus control immediately after hatching, northern bobwhite chicks (Colinus virginianus) pecked for brief heat presentations while hearing a high-pitched sound repeated at two constant rates: an S+ tempo signaling a rich reinforcement schedule, alternating with an S− tempo signaling a leaner schedule. Tempo generalization was then assessed in extinction. The expected excitatory gradients were produced after a threshold number of training sessions; unexpectedly, below that threshold, gradients were inhibitory. The chicks’ rapidly developing thermoregulatory capability may have resulted in a change from perceived negative reinforcement initially to positive reinforcement later. Given past research showing excitatory gradients after negative reinforcement, we suggest that these results demonstrate that all negative reinforcement is not equivalent, and, further, that classical conditioning effects require consideration.     

Mechanical behaviour analyses of sap ascent in vascular plants

A pure mechanical anisotropic model of a tree trunk has been developed based on the 3D finite element method. It simulates the microscopic structure of vessels in the trunk of a European beech (Fagus sylvatica) in order to study and analyse its mechanical behaviour with different configurations of pressures in the conduits of xylem and phloem. The dependence of the strains at the inner bark was studied when sap pressure changed. The comparison with previously published experimental data leads to the conclusion that a great tensile stress—or ‘negative pressure’—must exist in the water column in order to achieve the measured strains if only the mechanical point of view is taken into account. Moreover, the model can help to design experiments where qualitatively knowing the strains and the purely mechanical behaviour of the tree is required.     

The role of the glycine triad in human glutathione synthetase

Experimental kinetics and computational modeling of human glutathione synthetase (hGS) support the significant role of the G-loop glycine triad (G369, G370, G371) for activity of this ATP-grasp enzyme. Enzyme kinetic experiments indicate that G369V and G370V mutant hGS have little activity (<0.7 and 0.3%, respectively, versus wild-type hGS). However, G371V retains ∼13% of the activity of wild-type hGS. With respect to G-loop:A-loop interaction in hGS, mutations at Gly369 and Gly370 decrease ligand binding and prevent active site closure and protection. This research indicates that Gly369 and Gly370 have essential roles in hGS, while Gly371 has a lesser involvement. Implications for glycine-rich ensembles in other phosphate-binding enzymes are discussed.     

Response of transgenic potato seedlings to allelopathic pressure and the effect of nutrients in the culture medium

Chinese farmers frequently use a wheat–potato cropping system. The land area planted to transgenic potatoes is increasing because transgenic potatoes have greater resistance to pests and diseases. However, little is known about the bio-compatibility of transgenic potatoes with wheat straw. The objective of this tissue culture study was to determine the allelopathic effects of wheat straw on transgenic potato seedlings. Seedlings were cultured on normal MS medium (normal treatment) and nutrient-deficient MS medium (acclimated treatment) and then transferred to MS medium, which contained wheat straw powder. Wheat straw powder inhibited potato seedling growth in both treatments. Among the parameters analyzed in this study, inhibition was greatest for plant fresh weight and least for plant height. The inhibitive effects of wheat straw were greater for seedling roots compared to shoots. Resistance to allelopathic pressure from wheat straw was greater in acclimated seedlings compared to normal seedlings. This suggested that previous pressure may have induced tolerance in the transgenic potato seedlings. Furthermore, growth inhibition of potato seedlings from the normal treatment increased as the amount of wheat straw powder in the culture medium increased. Calculations indicated that the presence of wheat straw would lead to a 55% reduction in the total biomass of normal potato seedlings compared to a 39% reduction for acclimated seedlings. Parameters such as net photosynthesis rate (Pn) and quantum yield (Y(II)) changed as the nutrient content of the culture medium increased or decreased, but the changes in the parameters were smaller for acclimated seedlings compared to normal seedlings. This suggests that nutrient status during the culture period could help transgenic potato seedlings adapt and compensate for energy loss from seedlings in defending against allelopathic pressure. In summary, the results show that previous exposure to pressures such as nutrient deficiency may increase the allelopathic pressure resistance of transgenic potato seedlings.     

Transgenic mice with -6A haplotype of the human angiotensinogen gene have increased blood pressure compared with -6G haplotype

Hypertension is a serious risk factor for cardiovascular disease, and the angiotensinogen (AGT) gene locus is associated with human essential hypertension. The human AGT (hAGT) gene has an A/G polymorphism at -6, and the -6A allele is associated with increased blood pressure. However, transgenic mice containing 1.2 kb of the promoter with -6A of the hAGT gene show neither increased plasma AGT level nor increased blood pressure compared with -6G. We have found that the hAGT gene has three additional SNPs (A/G at -1670, C/G at -1562, and T/G at -1561). Variants -1670A, -1562C, and -1561T almost always occur with -6A, and variants -1670G, -1562G, and -1561G almost always occur with -6G. Therefore, the hAGT gene may be subdivided into either -6A or -6G haplotypes. We show that these polymorphisms affect the binding of HNF-1α and glucocorticoid receptor to the promoter, and a reporter construct containing a 1.8-kb hAGT gene promoter with -6A haplotype has 4-fold increased glucocorticoid-induced promoter activity as compared with -6G haplotype. In order to understand the physiological significance of these haplotypes in an in vivo situation, we have generated double transgenic mice containing either the -6A or -6G haplotype of the hAGT gene and the human renin gene. Our ChIP assay shows that HNF-1α and glucocorticoid receptor have stronger affinity for the chromatin obtained from the liver of transgenic mice containing -6A haplotype. Our studies also show that transgenic mice containing -6A haplotype have increased plasma AGT level and increased blood pressure as compared with -6G haplotype. Our studies explain the molecular mechanism involved in association of the -6A allele of the hAGT gene with hypertension.