Pollen tube growth and the pollen‐tube pathway of Nymphaea odorata (Nymphaeaceae)

An important aspect of the evolution of carpel closure, or angiospermy, is the relationship between pollen tube growth patterns and internalization of the pollen‐tube pathway. True carpel closure, involving postgenital fusion of inner carpel margins, is inferred to have arisen once within the ancient order Nymphaeales, in the common ancestor of Nymphaeaceae. We studied pollen tube development, from pollination to fertilization, in a natural population of Nymphaea odorata, using hand pollinations and timed flower collections. Pollen germinates in stigmatic secretions within 15 min and pollen tubes enter subdermal transmitting tissue within an hour, following wide intercellular spaces towards the zone of postgenital fusion. At the zone of fusion they turn downwards to grow in narrow spaces between interlocked cells and then wander freely to ovules within ovarian secretions. The pollen‐tube pathway is 2–6 mm long and upper ovules are first penetrated 2.5 h after pollination. Pollen tubes grow at rates of approximately 1 mm/h whether in stigmatic fluid, transmitting tissues or ovarian secretions. Pollen‐tube pathways are structurally diverse across Nymphaeales, yet their pollen tubes have similar morphologies and rapid growth rates. This pattern suggests pollen tube growth innovations preceded and were essential for the evolution of complete carpel closure. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 581–593.     

荞麦属植物淀粉酶和甲酸脱氢酶同功酶研究(英文)

以聚丙烯酰胺凝胶电泳方法研究了荞麦属植物8个种42个收集系干种子和发芽种子的淀粉酶和甲酸脱氢酶同功酶。结果表明,荞麦淀粉酶在于种子中缺乏活性,但是在发芽种子中活性很强。在供试材料的发芽种子中共发现23个淀粉酶谱带,其中甜荞和苦荞分别有10条和8条。不同荞麦种间淀粉酶谱带差异很大,但是同种内不同收集系间差异较小。谱带聚类分析表明大野荞和毛野荞分别与甜荞和苦荞较近缘,支持它们分别为甜荞和苦荞祖先种的假说。在干种子和发芽种子中,发现所有荞麦种类均只有1条位置一致的甲酸脱氢酶谱带,暗示该酶在进化中具有高度稳定性。     

The crystal structure of the Dps2 from Deinococcus radiodurans reveals an unusual pore profile with a non-specific metal binding site

The crystal structure of recombinant Dps2 (DRB0092, DNA protecting protein under starved conditions) from the Gram-positive, radiation-resistant bacterium Deinococcus radiodurans has been determined in its apo and iron loaded states. Like other members of the Dps family, the bacterial DrDps2 assembles as a spherical dodecamer with an outer shell diameter of 90 A and an interior diameter of 40 A. A total of five iron sites were located in the iron loaded structure, representing the first stages of iron biomineralisation. Each subunit contains a mononuclear iron ferroxidase centre coordinated by residues highly conserved amongst the Dps family of proteins. In the structures presented, a distinct iron site is observed 6.1 A from the ferroxidase centre with a unique ligand configuration of mono coordination by the protein and no bridging ligand to the ferroxidase centre. A non-specific metallic binding site, suspected to play a regulative role in iron uptake/release from the cage, was found in a pocket located near to the external edge of the C-terminal 3-fold channel.     

Mitochondrial DNA sequence diversity and origin of Chinese domestic yak

In order to clarify the origin and genetic diversity of yak in China, we analysed mitochondrial DNA (mtDNA) control region sequences (approximately 891 bp) in 52 individuals from four domestic yak (Poephagus grunniens) breeds, as well as from a hybrid between yak and cattle (Pianniu). Twenty-five samples were further selected for partial (420 bp) cytochrome b sequencing based on control region sequence information. Two yak samples shared sequences with Chinese cattle (Bos taurus); the remaining yak mtDNAs converged into two major clades in the phylogenetic analysis. Genetic diversity varied substantially among the breeds, with the hybrid Pianniu yak demonstrating the highest diversity. Our results suggest that the Chinese yak was domesticated from two distinct matrilineal sources or from a heterogeneous pool containing both divergent lineages, with occasional gene introgression from cattle.     

Changes in photosynthetic electron transfer and state transitions in an herbicide-resistant D1 mutant from soybean cell cultures

Anomalies in photosynthetic activity of the soybean cell line STR7, carrying a single mutation (S268P) in the chloroplastic gene psbA that codes for the D1 protein of the photosystem II, have been examined using different spectroscopic techniques. Thermoluminescence emission experiments have shown important differences between STR7 mutant and wild type cells. The afterglow band induced by both white light flashes and far-red continuous illumination was downshifted by about 4 °C and the Q band was upshifted by 5 °C. High temperature thermoluminescence measurements suggested a higher level of lipid peroxidation in mutant thylakoid membranes. In addition, the reduction rate of P700⁺ was significantly accelerated in STR7 suggesting that the mutation led to an activation of the photosystem I cyclic electron flow. Modulated fluorescence measurements performed at room temperature as well as fluorescence emission spectra at 77 K revealed that the STR7 mutant is defective in state transitions. Here, we discuss the hypothesis that activation of the cyclic electron flow in STR7 cells may be a mechanism to compensate the reduced activity of photosystem II caused by the mutation. We also propose that the impaired state transitions in the STR7 cells may be due to alterations in thylakoid membrane properties induced by a low content of unsaturated lipids.     

莪术基源及其活性成分开发利用

本文就莪术的植物种源,种质多样性,无性快繁和高产细胞悬浮体系的建立,活性成分分析、鉴别和结构解析,成分提取和分离,生理活性及其作用机理,剂型和结构改造等方面的研究成果进行了综述,对尚待深入研究的一些问题进行了探讨。     

The concept of correlated progression as the basis of a model for the evolutionary origin of major new taxa

Understanding the evolutionary processes responsible for the long treks through morphospace associated with the origin of new higher taxa is hampered by the lack of a realistic and usable model that accounts for long-term phenotypic evolvability. The systems-related concept of correlated progression, in which all the traits are functionally linked and so constrained to evolve by small increments at a time in parallel with each other, provides the basis for such a model. Implications for the process of evolution at high taxonomic level are that: the evolving traits must be considered together as a system, and the exact sequence of incremental changes in characters is indeterminable; there are no identifiable key innovations; selection acts on the phenotype as a whole rather than on individual traits; and the selection force is therefore multidimensional. Application of the model to the pattern of evolution of traits and trait states as revealed by the fossil record of the stem groups of such taxa as mammals, turtles and tetrapods generates realistic testable hypotheses about how such groups evolved.     

On the problem of the origin of Pogonophora

A number of embryological features of the Pogonophora suggest that they could not derive from the Polychaeta and are closely related to Deuterostomia. These are: (1) traces of spiral cleavage that sharply differ the from cleavage of polychaetes in the prospective value of blastomeres; (2) enterocoelic formation of mesoderm; (3) the larva most closely resembles Balanoglossus that has just completed metamorphosis; proto-, meso-, and metasoma of pogonophoran larva correspond (or are homologous) to the proboscis, collar, and trunk of Balanoglossus respectively; while the telosoma can be regarded as an organ appearing late in phylogenesis that serves to burrow into the bottom; (4) larvae of Siboglinum have a transitory mouth located, as it is the case in Enteropneusta, between proto-and mesosoma, very far from the posterior end, where there is closed blastopore; therefore, the former can be considered as a secondary mouth; (5) the asymmetrical development of the anterior pair of coeloms in Pogonophora, Echinodermata, and Amphioxus allows finding homologies between organs developing from these coeloms.     

Farm‐scale assessment of movement patterns and colonization dynamics of the grain aphid in arable crops and hedgerows

1 Integrated management of crop pests requires the identification of the appropriate spatial scale at which colonization processes occurs. We assessed, by coupling demographic and genetic methods, the relative contribution of local and transient migrants of the grain aphid Sitobion avenae to wheat field colonization in spring. 2 We examined, during two consecutive years, the daily colonization of wheat by aphid migrants and compared this with daily aphid flight monitored by a local 12.2‐m suction trap. The genetic profiles of aphids landing on crops were compared with those of both flying aphids caught by the suction trap and local populations from arable crops and hedgerows. 3 In the first year, we observed: (i) a strong correlation between aphids colonizing the crop and those moving within the crop and a close genetic similarity between aphids from these samples and (ii) a high level of genetic differentiation between these aphids and populations from local cereals and field margins. In the second year, the number of migrants recorded on the wheat was three‐fold higher than in the previous year, and less correlated with that recorded by the suction trap. This was associated with a lack of genetic differentiation between all samples. 4 This variation in the colonization processes resulted mainly in an abrupt increase in abundance of genotypes from local over‐wintering sites in 2004. This suggests that, despite the long range dispersal potential of the grain aphid, outbreak risks could be mainly determined at a local scale, encouraging the design of relatively small management units.