盾叶薯蓣雄花发育、小孢子发生及雄配子体发育的研究

大部分盾叶薯蓣为雌雄异株植物。在湖南省长沙市气候条件下,雄花花期为4月初至9月中。雄花花器小,每日17:30~19:30开放。小孢子母细胞减数分裂过程中,细胞质分裂为连续型,四分体为十字形。花药壁发育过程中,中层两层细胞紧贴,解体较早;绒毡层为腺质绒毡层,兼有部分变形绒毡层特征。     

Dioscorin isolated from Dioscorea alata activates TLR4-signaling pathways and induces cytokine expression in macrophages

The Toll-like receptor 4 (TLR4)-signaling pathway is crucial for activating both innate and adaptive immunity. TLR4 is a promising molecular target for immune-modulating drugs, and TLR4 agonists are of therapeutic potential for treating immune diseases and cancers. Several medicinal herb-derived components have recently been reported to act via TLR4-dependent pathways, suggesting that medicinal plants are potential resources for identifying TLR4 activators. We have applied a screening procedure to systematically identify herbal constituents that activate TLR4. To exclude possible LPS contamination in these plant-derived components, a LPS inhibitor, polymyxin B, was added during screening. One of the plant components we identified from the screening was dioscorin, the glycoprotein isolated from Dioscorea alata. It induced TLR4-downstream cytokine expression in bone marrow cells isolated from TLR4-functional C3H/HeN mice but not from TLR4-defective C3H/HeJ mice. Dioscorin also stimulated multiple signaling molecules (NF-kappaB, ERK, JNK, and p38) and induced the expression of cytokines (TNF-alpha, IL-1beta, and IL-6) in murine RAW 264.7 macrophages. Furthermore, the ERK, p38, JNK, and NF-kappaB-mediated pathways are all involved in dioscorin-mediated TNF-alpha production. In summary, our results demonstrate that dioscorin is a novel TLR4 activator and induces macrophage activation via typical TLR4-signaling pathways.     

New starches from traditional Chinese medicine (TCM)--Chinese yam (Dioscorea opposita Thunb.) cultivars

The starches separated from two different Dioscorea opposita Thunb. cultivars were investigated for morphological, thermal and crystal properties. The shape of starch granules separated from different D. opposita Thunb. cultivars varied from round to oval or irregular. The surface of the starch granules appeared to be smooth without any fissures. The average particle diameter of starches from different D. opposita Thunb. cultivars was 40.3 and 38.7mum for D. 47 and D. SXY starch, respectively. The transition temperatures (T(o), T(p) and T(c)) and enthalpy of gelatinization (DeltaH(gel)) were determined using differential scanning calorimetry (DSC). The D. SXY starch showed the lower T(o) (74.2 degrees C) and the broader R (12.4). T(p) and T(c) of starch from D. 47 were higher than that of D. SXY starch. DeltaH(gel) values (11.37J/g) of D. 47 was higher than that of D. SXY starch (10.78J/g). The crystal type of starches separated from two different D. opposita cultivars was a typical C-type pattern. The degree of crystallinity of two D. opposita cultivars starches was about 45.9% and 31.5%, respectively.     

Fruit fly behavior in response to chemosensory signals

An important question in contemporary sensory neuroscience is how animals perceive their environment and make appropriate behavioral choices based on chemical perceptions. The fruit fly Drosophila melanogaster exhibits robust tastant and odor-evoked behaviors. Understanding how the gustatory and olfactory systems support the perception of these contact and volatile chemicals and translate them into appropriate attraction or avoidance behaviors has made an unprecedented contribution to our knowledge of the organization of chemosensory systems. In this review, I begin by describing the receptors and signaling mechanisms of the Drosophila gustatory and olfactory systems and then highlight their involvement in the control of simple and complex behaviors. The topics addressed include feeding behavior, learning and memory, navigation behavior, neuropeptide modulation of chemosensory behavior, and I conclude with a discussion of recent work that provides insight into pheromone signaling pathways.     

Early F-actin disorganization may be signaling vacuole disruption in incompatible pollen tubes of Nicotiana alata

Self-incompatibility (SI) systems appeared early in plant evolution as an effective mechanism to promote outcrossing and avoid inbreeding depression. These systems prevent self-fertilization by the recognition and rejection of self-pollen and pollen from closely related individuals. The most widespread SI system is based on the action of a pistil ribonuclease, the S-RNase, which recognizes and rejects incompatible pollen. S-RNases are endocyted by pollen tubes and stored into vacuoles. By a mechanism that is still unknown, these vacuoles are selectively disrupted in incompatible pollen, releasing S-RNases into the cytoplasm and allowing degradation of pollen RNA. Recently, we have studied the timing of in vivo alterations of pollen F-actin cytoskeleton after incompatible pollinations. Besides being essential for pollen growth, F-actin cytoskeleton is a very dynamic cellular component. Changes in F-actin organization are known to be capable of transducing signaling events in many cellular processes. Early after pollination, F-actin showed a progressive disorganization in incompatible pollen tubes. However by the time the F-actin was almost completely disrupted, the large majority of vacuolar compartments were still intact. These results indicate that in incompatible pollen tubes F-actin disorganization precedes vacuolar disruption. They also suggest that F-actin may act as an early transducer of signals triggering the rejection of incompatible pollen.     

柴黄姜的传粉生物学特性

对产自湖北武当山的柴黄姜（Dioscorea nipponica subsp．rosthornii Prain et Burkill）的花部特征和访花昆虫种类及访花行为、访花频率和携粉量进行了研究,并对柴黄姜的传粉方式、结实和种子萌发状况进行了检测。结果表明,柴黄姜具有虫媒花的典型花部特征,共观测到访花昆虫4目34种,其中传粉昆虫6种,隧蜂属（Halictus sp．）和地蜂属（Andrena sp．）的2种昆虫是柴黄姜的主要传粉昆虫。访花昆虫对雄株的访花高峰时段为11：00至14：00,对雌花没有明显的访花高峰时段。在自然条件下,柴黄姜的座果率为18．86％,结实率为7．12％,种子萌发率为64．76％。在武当山,柴黄姜种群扩展仍以有性繁殖为主,无性繁殖为重要补充。     

Identification of structure and antioxidant activity of a fraction of polysaccharide purified from Dioscorea nipponica Makino

A large number of polysaccharides are present in boiling-water extraction of Dioscorea nipponica Makino. A DEAE-Sepharose CL-6B column chromatography was used to isolate the major polysaccharides from D. nipponica Makino. The largest amount of fraction of polysaccharide was subjected to further purification by gel-filtration on Sephadex G-100. The purified fraction was a neutral polysaccharide and a single peak in HPLC with Sugar KS-804 column, with a molecular weight of 38,000, and comprised mainly of glucose and fructose (45:1). Analysis by Periodate oxidation–Smith degradation indicated that there were 5.9%(1→)-glycosidic linkages, 4.94% (1 → 2)-glycosidic linkages, 61.16% (1 → 4)-glycosidic linkages, and 28% (1 → 3)-glycosidic linkages. On the basis of superoxide radical assay, hydroxyl radical assay, and self-oxidation of 1,2,3-phentriol assay, its antioxidant activity was investigated. This purified fraction of polysaccharide exhibited equivalent inhibiting power for self-oxidation of 1,2,3-phentriol to Vc, a little higher scavenging activity of superoxide radical and hydroxyl radical than Vc, and should be explored as a novel potential antioxidant.     

Heritability and correlation structure of nectar and floral morphology traits in Nicotiana alata

The heritability and genetic basis of nectar traits have been rarely studied in the field, where plants are exposed to environmental factors that could mask underlying genetic effects. Heritabilities and variance components were estimated for nectar and morphological traits of Nicotiana alata , using a partial diallel design. The main experiment was conducted in a Missouri experimental garden using a randomized block design with three plant density treatments, whereas a smaller experiment was conducted near native Brazil habitat to compare the environmental variance in traits between Missouri and Brazil. Significant heritability was detected for nectar volume and energy content, and for corolla tube length. Phenotypic correlations were significant between all traits investigated, whereas significant genetic correlations were only found between nectar volume and energy and between corolla limb width and mouth diameter. There were no significant family-by-density interactions detected in the Missouri field environment. All traits differed significantly between Missouri and Brazil environments, but significant genetic by environment (G × E) interactions between Missouri and Brazil were detected for only one trait. This study shows that nectar traits can be heritable despite considerable environmental variation.     

Life history variation between species of the relictual genus Borderea (Dioscoreaceae): phylogeography, genetic diversity, and population genetic structure assessed by RAPD markers

The genus Borderea consists of two species, B. pyrenaica and B. chouardii, taxa which have been previously considered as conspecific due to their overall close morphology. These two sole species of the rare genus of Dioscoreaceae are endemic to the Pyrenees (Spain, France). This mountain range likely operated as a refugium for these plants during the last glaciations. B. chouardii is only known from a single population in the Spanish Prepyrenees and has been classified as at risk of extinction in the Red List of Endangered Species (IUCN); B. pyrenaica shows a narrow distribution range in the central Pyrenees and Prepyrenees. We analysed genetic variation, population structure and differentiation in these two taxa using RAPD markers. Our study was conducted on the same seven populations for which very low levels of genetic differentiation were detected previously through allozyme analysis. By contrast, high levels of genetic variability were detected through the RAPD hypervariable markers. Twelve RAPD primers produced 112 distinct bands in the 397 surveyed individuals, totalling 395 different RAPD phenotypes. Only four bands were monomorphic across all samples of Borderea, whereas 21 of the polymorphic bands were species‐specific (20 for B. chouardii, and one for B. pyrenaica). The largest genetic distances were those between the B. chouardii and the B. pyrenaica phenotypes. An analysis of molecular variance showed greater variance between groups (B. chouardii vs. B. pyrenaica, 76.08%) than within groups (3.60%). RAPD band specificity, phenotypic distances, and the partitioning of variance all support the taxonomic separation of the two species. Statistical evaluation of within‐ and among‐population RAPD genetic variability in B. pyrenaica showed that genetic variability was higher within populations (>80%) than among them. No clear pattern of RAPD differentiation could be observed among the six studied populations of this taxon though slight differences in genetic diversity could be observed in the more isolated Prepyrenean populations compared with the more widespread Pyrenean ones. These results suggest a recent postglacial origin of the present B. pyrenaica populations. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80 , 483–498.     

Temperature dependence of seedling establishment of a perennial, Dioscorea tokoro

The temperature dependence of seed germination and seedling growth was analyzed in Dioscorea tokoro, an East Asian summer-green perennial. Seeds were able to germinate fully only at 11°–20°C. At around 17°–20°C the first leaf petiole of the seedling elongated and quickly set the first leaf blade at a position enabling photosynthesis. At temperatures higher than 20°C petiole elongation was retarded, and seedlings formed a rhizome and established as a perennial. The rhizome size increased with temperature up to 29°C. Thus, during growth immediately after germination, temperature appears to be a key factor in determining whether the plant establishes as a perennial or grows rapidly without rhizome thickening. Received: April 6, 2001 / Accepted: September 14, 2001