Pollination by deceit in Paphiopedilum barbigerum (Orchidaceae): a staminode exploits the innate colour preferences of hoverflies (Syrphidae)

Paphiopedilum barbigerum T. Tang et F. T. Wang, a slipper orchid native to southwest China and northern Vietnam, produces deceptive flowers that are self‐compatible but incapable of mechanical self‐pollination (autogamy). The flowers are visited by females of Allograpta javana and Episyrphus balteatus (Syrphidae) that disperse the orchid’s massulate pollen onto the receptive stigmas. Measurements of insect bodies and floral architecture show that the physical dimensions of these two fly species correlate with the relative positions of the receptive stigma and dehiscent anthers of P. barbigerum. These hoverflies land on the slippery centralised wart located on the shiny yellow staminode and then fall backwards through the labellum entrance. They are temporarily trapped in the inflated chamber composed of the interconnected labellum and column. The attractive staminode of P. barbigerum strongly reflects the colour yellow (500–560 nm), a colour preferred innately by most pollen‐eating members of the Syrphidae. No scent molecules were detected using GC mass spectrometry analysis, showing that the primary attractant in this system is visual, not olfactory. Pollination‐by‐deceit in P. barbigerum is contrasted with its congener, P. dianthum, a brood site mimic that is pollinated by ovipositing females of E. balteatus. As the natural rate of fruit set in P. barbigerum (mean 26.3% pooled over three seasons) is lower than that of P. dianthum (mean 58.5% over two seasons), the evolution of false brood sites in some Paphiopedilum spp. should be selectively advantageous as they may provide an increase in the attention and return rates of dependable pollinators to flowers that always lack a reward.     

Improving transmembrane protein consensus topology prediction using inter-helical interaction

Alpha helix transmembrane proteins (αTMPs) represent roughly 30% of all open reading frames (ORFs) in a typical genome and are involved in many critical biological processes. Due to the special physicochemical properties, it is hard to crystallize and obtain high resolution structures experimentally, thus, sequence-based topology prediction is highly desirable for the study of transmembrane proteins (TMPs), both in structure prediction and function prediction. Various model-based topology prediction methods have been developed, but the accuracy of those individual predictors remain poor due to the limitation of the methods or the features they used. Thus, the consensus topology prediction method becomes practical for high accuracy applications by combining the advances of the individual predictors. Here, based on the observation that inter-helical interactions are commonly found within the transmembrane helixes (TMHs) and strongly indicate the existence of them, we present a novel consensus topology prediction method for αTMPs, CNTOP, which incorporates four top leading individual topology predictors, and further improves the prediction accuracy by using the predicted inter-helical interactions. The method achieved 87% prediction accuracy based on a benchmark dataset and 78% accuracy based on a non-redundant dataset which is composed of polytopic αTMPs. Our method derives the highest topology accuracy than any other individual predictors and consensus predictors, at the same time, the TMHs are more accurately predicted in their length and locations, where both the false positives (FPs) and the false negatives (FNs) decreased dramatically. The CNTOP is available at: http://ccst.jlu.edu.cn/JCSB/cntop/CNTOP.html.     

AIB1 is required for the acquisition of epithelial growth factor receptor-mediated tamoxifen resistance in breast cancer cells

Acquired resistance to tamoxifen has become a serious obstacle in breast cancer treatment. The underlying mechanism responsible for this condition has not been completely elucidated. In this study, a tamoxifen-resistant (Tam-R) MCF-7 breast cancer cell line was developed to mimic the occurrence of acquired tamoxifen resistance as seen in clinical practice. Increased expression levels of HER1, HER2 and the estrogen receptor (ER)-AIB1 complex were found in tamoxifen-resistant cells. EGF stimulation and gefitinib inhibition experiments further demonstrated that HER1/HER2 signaling and AIB1 were involved in the proliferation of cells that had acquired Tam resistance. However, when AIB1 was silenced with AIB1-siRNA in Tam-R cells, the cell growth stimulated by the HER1/HER2 signaling pathway was significantly reduced, and the cells were again found to be inhibited by tamoxifen. These results suggest that the AIB1 protein could be a limiting factor in the HER1/HER2-mediated hormone-independent growth of Tam-R cells. Thus, AIB1 may be a new therapeutic target, and the removal of AIB1 may decrease the crosstalk between ER and the HER1/HER2 pathway, resulting in the restoration of tamoxifen sensitivity in tamoxifen-resistant cells.     

Simple modifications of the serpin reactive site loop convert SCCA2 into a cysteine proteinase inhibitor: a critical role for the P3' proline in facilitating RSL cleavage

The human squamous cell carcinoma antigens (SCCA) 1 and 2 are members of the serpin family that are 92% identical in their amino acid sequence. Despite this similarity, they inhibit distinct classes of proteinases. SCCA1 neutralizes the papain-like cysteine proteinases, cathepsins (cat) S, L, and K; and SCCA2 inhibits the chymotrypsin-like serine proteinases, catG and human mast cell chymase. SCCA2 also can inhibit catS, as well as other papain-like cysteine proteinases, albeit at a rate 50-fold less than that of SCCA1. Analysis of the mechanism of inhibition by SCCA1 revealed that the reactive site loop (RSL) is important for cysteine proteinase inhibition. The inhibition of catS by a mutant SCCA2 containing the RSL of SCCA1 is comparable to that of wild-type SCCA1. This finding suggested that there were no motifs outside and only eight residues within the RSL that were directing catS-specific inhibition. The purpose of this study was to determine which of these residues might account for the marked difference in the ability of SCCA1 and SCCA2 to inhibit papain-like cysteine proteinases. SCCA2 molecules containing different RSL mutations showed that no single amino acid substitution could convert SCCA2 into a more potent cysteine proteinase inhibitor. Rather, different combinations of mutations led to incremental increases in catS inhibitory activity with residues in four positions (P1, P3', P4', and P11') accounting for 80% of the difference in activity between SCCA1 and SCCA2. Interestingly, the RSL cleavage site differed between wild-type SCCA2 and this mutant. Moreover, these data established the importance of a Pro residue in the P3' position for efficient inhibition of catS by both wild-type SCCA1 and mutated SCCA2. Molecular modeling studies suggested that this residue might facilitate positioning of the RSL within the active site of the cysteine proteinase.     

Diallyl disulfide from garlic oil inhibits Pseudomonas aeruginosa virulence factors by inactivating key quorum sensing genes

Applied Microbiology and Biotechnology - Garlic oil can disrupt the quorum sensing (QS) pathways of the opportunistic pathogen Pseudomonas aeruginosa; however, the underlying mechanisms for this...     

Mechanisms of the vasorelaxant effect of 1-hydroxy-2, 3, 5-trimethoxy-xanthone, isolated from a Tibetan herb, Halenia elliptica, on rat coronary artery

1-Hydroxy-2, 3, 5-trimethoxyxanthone (HM-1) is a xanthone isolated from Halenia elliptica, a Tibetan medicinal herb. HM-1 (0.33-42.1 microM) produced a concentration-dependent relaxation in rat coronary artery rings pre-contracted with 1 microM 5-hydroxytryptamine (5-HT), with an EC(50) of 1.67+/-0.27 microM. Removal of the endothelium significantly affected the vasodilator potency of HM-1, resulting in 46% decrease in E(max) value. The endothelium-dependent effects of HM-1 was confirmed when its vasorelaxant effect was inhibited after addition of nitric oxide synthase (NOS) inhibitor N(omega)-nitro-l-arginine methyl ester (100 microM) or the soluble guanylate cyclase inhibitor 1H-[1, 2, 4] oxadiazolo [4,3-alpha] quinoxalin-1-one (ODQ, 10 microM). Atropine (100 nM), flurbiprofen (10 microM), propranolol (100 microM), pyrilamine (10 microM), cimetidine (10 microM) and SQ22536 (100 microM) had no effect on the vasorelaxant activity of HM-1 indicated the non-involvement of other receptor/enzyme systems. In endothelium-denuded coronary artery rings, the vasorelaxant effect of HM-1 was unaffected by potassium channel blockers such as tetraethylammonium (10 mM), iberiotoxin (100 nM), barium chloride (100 microM) and 4-aminopyridine (1 mM). The involvement of Ca(2+) channel in 5-HT-primed artery ring preparations incubated with Ca(2+)-free buffer was confirmed when HM-1 (9.93 microM) partially abolished the CaCl(2)-induced vasoconstriction (87% inhibition in intact-endothelium artery rings; 50% inhibition in endothelium-denuded rings). In the KCl-primed preparations incubated with Ca(2+)-free buffer, HM-1 (9.93 microM) produced a 27.3% inhibition in endothelium-denuded rings. HM-1 (3.31-33.1 microM) had minimal relaxant effects (14.4%-20.3%) on the contractile response generated by 10 microM phorbol 12,13-diacetate (PDA) in Ca(2+)-free solutions, suggesting minimal effects on intracellular Ca(2+) mechanisms. These findings suggest the vasodilator action of HM-1 involved both an endothelium-dependent mechanism involving NO and an endothelium-independent mechanism by inhibiting Ca(2+) influx through L-type voltage-operated Ca(2+) channels; a minor contribution to the effects of HM-1 may be related to inhibition of the protein kinase C-mediated release of intracellular Ca(2+) stores.     

低能铁离子束对原卟啉IX二钠盐的辐照效应研究

110ke V Fe^ 离子注入原卟啉IX二钠盐薄膜亲品后的一些谱学分析结果表明,低能铁离子束辐照可以导致生物分子的损伤和化学改性,并且初步证实注入铁离子在样品分子中慢化沉积后形成含铁的金属络合物,即注入铁离子的质量沉积。     

Involvement of cell proliferation in the process of follicular atresia in the guinea pig

Cell morphology and proliferation was investigated in the atretic follicles during estrous cycles in the guinea pig. Ovarian samples on days 1, 4, 8, 12 and 16 of the estrous cycle in the guinea pig were taken in the morning for histologic staining with hematoxylin and eosin (HE), and immunohistochemical staining of the protein proliferating cell nuclear antigen (PCNA). The results indicated that the granulosa cells degenerated and eliminated first in atretic follicles, while the fibroblast-like cells appeared in the innermost layer of theca interna cells. When the fibroblast-like cells migrated to the antrum, they proliferated and formed a new tissue in peripheral to the zona pellucida of the oocyte. Our results also revealed that the orientation of the theca interna cell arrangement changed twice during the process of atresia, and the loose connective tissue in the antrum was critical for follicular atresia. Therefore, follicular atresia was not a simple process of cell death and elimination, but coexisted with cell proliferation. To our knowledge, we have for the first time confirmed cell proliferation and the presence of new tissue in atretic follicles in guinea pigs.     

鳞木目小孢子叶球山西鳞孢穗（新种）的解剖特征

描述了山西太原西山煤田太原组７号煤层煤核中一种鳞木目的小孢子叶球——山西鳞孢穗（新种）（Ｌｅｐｉｄｏｓｔｒｏｂｕｓｓｈａｎｘｉｅｎｓｅ ｓｐ． ｎｏｖ．）。其主要特征是：孢子叶球较小,长３．５ ｃｍ 以上,直径１．６～１．８ ｃｍ 。轴具管状中柱,孢子叶螺旋状着生于轴上。孢子叶柄长６～７ ｍ ｍ ,远端叶片长１．２ ｃｍ 以上。孢子叶柄具翅,翅长２～２．５ ｍ ｍ 。小孢子囊可能呈袋形,长与孢子叶柄相近,宽约４．５ ｍ ｍ ,高２～３ ｍ ｍ ,以其长度的约２／３着生于孢子叶柄的腹面上。成熟的孢子囊壁仅由一层柱状细胞构成。小孢子直径６８～７７ μｍ ,具三缝,远极面具短刺