中国高等植物多样性

据最新资料统计,中国有野生高等植物454科3,818属35,112种。其中,苔藓植物151科602属3,045种;蕨类植物38科176属2,124种;裸子植物8科37属227种;被子植物257科3,003属29,716种。根据世界高等植物多样性相关研究数据,中国的苔藓、蕨类、裸子植物和被子植物物种多样性分别占世界的18.8%、17.7%、22.2%和11.1%。中国高等植物特有属共212属,其中苔藓7属、蕨类2属、裸子植物7属、被子植物196属;特有种共17,439种,其中苔藓524种、蕨类840种、裸子植物115种、被子植物15,960种;特有种比例分别为17.2%、39.6%、50.7%和53.7%。因此,中国高等植物中国特有种的比例为49.7%,维管植物为52.8%,种子植物为53.7%。物种多样性最高的前10个科依次为:菊科(227属/2,315种)、禾本科(215/1,787)、豆科(141/1,631)、兰科(205/1,556)、唇形科(103/975)、毛茛科(38/957)、蔷薇科(53/954)、莎草科(32/871)、杜鹃花科(22/841)和茜草科(94/696)。特有属最多的前12个科依次为:苦苣苔科(26属)、菊科(18)、兰科(14)、唇形科(11)、伞形科(9)、十字花科(9)、夹竹桃科(6)、禾本科(6)、野牡丹科(5)、紫草科(4)、茜草科(4)和毛茛科(4)。物种多样性最高的前10个属依次为:杜鹃花属(Rhododendron)(588种)、薹草属(Carex)(537)、黄芪属(Astragalus)(420)、马先蒿属(Pedicularis)(363)、紫堇属(Corydalis)(357)、报春花属(Primula)(310)、风毛菊属(Saussurea)(293)、柳属(Salix)(279)、凤仙花属(Impatiens)(274)和龙胆属(Gentiana)(255)。特有种最多的前10个属依次为:杜鹃花属(433种)、马先蒿属(283)、薹草属(273)、紫堇属(258)、黄芪属(237)、凤仙花属(234)、报春花属(222)、小檗属(Berberis)(209)、楼梯草属(Elatostema)(207)和风毛菊属(196)。物种数目超过5,000种的省区依次为:云南(15,900种)、四川(10,374)、西藏(7,629)、广西(7,399)、贵州(6,405)、广东(5,498)和台湾(5,290)。在17个世界生物多样性大国中,按物种多样性排序,中国略低于巴西,位列第四;按照物种特有比例排序,中国略高于菲律宾,位列第七。     

Identification of acquired thermotolerance deficiency within the ditelosomic series of `Chinese Spring' wheat

The relative contribution of individual heat shock proteins to acquired thermotolerance was evaluated through analysis of chromosomal deletions in a ditelosomic series of the hexaploid wheat (Triticum aestivum L.) cultivar `Chinese Spring'. This study describes the identification of a line within this ditelosomic series that exhibited a reduced level of acquired thermotolerance. Changes in the temperature sensitivity of chlorophyll accumulation were used as an indicator of acquired thermotolerance. The temperature providing maximum chlorophyll accumulation was 30 °C in leaves under continuous light. A 30-min challenge temperature of 48 °C prior to the light exposure was shown to inhibit subsequent chlorophyll accumulation. Preincubation at 40 °C for 4 h before the 30-min 48 °C challenge triggered the acquired thermotolerance system of the plant resulting in chlorophyll accumulation upon exposure to light. Evaluation of the ditelosomic series revealed reductions in acquired thermotolerance levels in the DT7DS line relative to controls. Two-dimensional SDS polyacrylamide gel analysis was used to identify reduction in the level of two low molecular mass heat shock proteins in DT7DS.     

Cryoconservation of South African plant genetic diversity

South Africa has a rich flora which exhibits among the highest species density in the world, distributed across nine biomes that support an impressive diversity of animal life. However, a variety of human actions, invasion by alien species, natural disturbances and climate change collectively impact negatively on the great diversity of both plant and animal species. In situ conservation has long been practised, primarily in nature reserves, complemented by ex situ conservation in national botanic gardens, but in vitro plant conservation is not common. In the context of animal biodiversity conservation, the Wildlife Biological Resource Centre of the National Zoological Gardens utilises cryobanking as one of its major focuses and is now poised to expand as the repository for the cryoconservation of plant germplasm, particularly for indigenous recalcitrant-seeded and poor-seeding species. However, there are particular problems associated with successful germplasm cryostorage of such tropical and subtropical plants. As we see the science and application of cryobiology and cryoconservation as cross-cutting and transdisciplinary, we have entrained formal networking among scientists offering a range of specialisations aimed at a deeper understanding of common problems and practical outcomes to facilitate both plant and animal biobanking. The endeavours are aimed at elucidating the basis of both successes and failures in our efforts to attain optimal outcomes. With focus on best practices, standard operating procedures, validation and risk management for cryopreserved and cold-stored plant and animal material, our ultimate aim is to facilitate restoration by the safe reintroduction of indigenous species.     

植物遗传多样性和系统学研究中的等位酶分析*

本文对“等位酶”的概念、等位酶分析方法在植物遗传多样性和系统学研究中应用的范围（包括种上和种下）进行了介绍和讨论,并对其优点和缺点进行了评论。认为等位酶分析是研究生物遗传多样性的重要方法,并为系统学和进化研究进入分子水平开辟了广阔而实用的前景,但使用分子资料并不意味着可以抛弃形态、细胞等其他方面的资料,它们的关系是互相补充,而决不是互相代替。     

植物遗传多样性和系统学研究中的等位酶分析*

本文对“等位酶”概念、等位酶分析方法在植物遗传多样性和系统学研究中应用的范围（包括种上和种下）进行了介绍和讨论,并对其优点和缺点进行了评论。认为等位酶分析是研究生物遗传多样性的重要方法,并为系统学和进化研究进入分子水平开辟了广阔而实用的前景,但使用分子资料并不意味着可以抛弃形态、细胞等其他方面的资料,它们的关系是互相补充,而决不是互相代替。     

佛坪国家级自然保护区植物群落物种多样性特征

用物种多样性指数（Simpson指数和Shannon指数）、均匀度指数（Pielou均匀度）和物种丰富度,对佛坪国家级自然保护区主要高等植物群落物种多样性进行了测度。结果表明：森林群落的多样性程度高于灌丛和草甸,落叶阔叶林高于针叶林,栎林高于杨桦林。群落物种多样性有随海拔高度的升高而降低的趋势。物种多样性在森林群落垂直结构上的分布特点,表现为一般乔木层与灌木层接近但低于草本层。     

Assessment of cytochrome P450 sequences offers a useful tool for determining genetic diversity in higher plant species

To investigate and develop new genetic tools for assessing genome-wide diversity in higher plant-species, polymorphisms of gene analogues of mammalian cytochrome P450 mono-oxygenases were studied. Data mining on Arabidopsis thaliana indicated that a small number of primer-sets derived from P450 genes could provide universal tools for the assessment of genome-wide genetic diversity in diverse plant species that do not have relevant genetic markers, or for which, there is no prior inheritance knowledge of inheritance traits. Results from PCR amplification of 51 plant species from 28 taxonomic families using P450 gene-primer sets suggested that there were at least several mammalian P450 gene mammalian-analogues in plants. Intra- and inter- specific variations were demonstrated following PCR amplifications of P450 analogue fragments, and this suggested that these would be effective genetic markers for the assessment of genetic diversity in plants. In addition, BLAST search analysis revealed that these amplified fragments possessed homologies to other genes and proteins in different plant varieties. We conclude that the sequence diversity of P450 gene-analogues in different plant species reflects the diversity of functional regions in the plant genome and is therefore an effective tool in functional genomic studies of plants.Communicated by C. Möllers     

Identification and genetic diversity of plum cultivars grown in Belarus

A study of the collection of sour cherry, sweet cherry, common plum, diploid and tetraploid types of plums, and apricots grown in Belarus carried out using 20 SSR markers showed that they are characterized by high genetic diversity. Among 106 genotypes, 524 polymorphic alleles were identified. The average number of alleles was 15.4 in common plum samples, 11.3 in diploid and tetraploid plum, 9.3 in sour cherry, 6.0 in apricot, and 4.9 in sweet cherry. The greatest genetic diversity is characteristic of common plum cultivars (PD = 0.811). The genetic diversity decreases as follows: diploid plum (PD = 0.741), sour cherry (PD = 0.721), apricot (PD = 0.673), and sweet cherry (PD = 0.655). Cluster analysis shows that the degree of intraspecific divergence in sour cherry and sweet cherry cultivars is less than that of common plum, diploid plum, and apricot plum. Although apricots and plums belong to the subgenus Prunophora, according to the results of SSR analysis, apricot cultivars form a cluster that is more distant from both Cerasus and Prunophora. A set of seven SSR markers (EMPA001, EMPA005, EMPA018, EMPA026 and BPPCT025, BPPCT026, BPPCT039) was selected for DNA identification of cultivars of sour cherry, sweet cherry, common plum, diploid plum, and apricot, as well as species and interspecies hybrids.     

Genetic diversity and conservation and utilization of plant genetic resources

Biodiversity refers to variation within the living world, while genetic diversity represents the heritable variation within and between populations of organisms, and in the context of this paper, among plant species. This pool of genetic variation within an inter-mating population is the basis for selection as well as for plant improvement. Thus, conservation of this plant genetic diversity is essential for present and future human well-being. During recent years, there has been increasing awareness of the importance of adopting a holistic view of biodiversity, including agricultural biodiversity, conservation for sustainable utilization and development. These principles have been enshrined in the Convention on Biological Diversity and the Global Plan of Action of the Food and Agriculture Organization of the United Nations. The emphasis is now to understand the distribution and extent of genetic diversity available to humans in plant species, so that the genetic diversity can be safely conserved and efficiently used. It is generally recognized that plant genetic diversity changes in time and space. The extent and distribution of genetic diversity in a plant species depends on its evolution and breeding system, ecological and geographical factors, past bottlenecks, and often by many human factors. Much of the large amount of diversity of a species may be found within individual populations, or partitioned among a number of different populations.A better understanding of genetic diversity and its distribution is essential for its conservation and use. It will help us in determining what to conserve as well as where to conserve, and will improve our understanding of the taxonomy and origin and evolution of plant species of interest. Knowledge of both these topics is essential for collecting and use of any plant species and its wild relatives. In order to mange conserved germplasm better, there is also a need to understand the genetic diversity that is present in collections. This will help us to rationalize collections and develop and adopt better protocols for regeneration of germplasm seed. Through improved characterization and development of core collections based on genetic diversity information, it will be possible to exploit the available resources in more valuable ways.     

Involvement of nitric oxide in acquired thermotolerance of rice seedlings

The role of nitric oxide (NO) in thermotolerance acquired by heat acclimation (38°C) was investigated. Results showed that 38°C acclimation, on the one hand, obviously reduced hydrogen peroxide (H₂O₂) and MDA contents and ion leakage degree in rice leaves; however, on the other hand, it increased the survival of rice (Oryza sativa L.) seedlings under 50°C heat stress. Application of nitric oxide donor, sodium nitroprusside (SNP), prior to 38°C acclimation dramatically increased the acquired thermotolerance. To elucidate the role of endogenous NO in acquired thermotolerance, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO, a specific NO scavenger) was used (scavengers are used to control the level of both exogenous and endogenous NO). Results showed that PTIO pretreatment resulted in the elimination of acquired thermotolerance induced by 38°C acclimation in rice seedlings. Nitric oxide (NO) release measurement indicated that there was indeed an abrupt elevation in the NO content in 40 min after 38°C acclimation, proving the involvement of NO in acquired thermotolerance inducement in rice seedling.     

Conserving plant genetic diversity for dependent animal communities

While population genetic diversity has broad application in species conservation, no studies have examined the community‐level consequences of this diversity. We show that population genetic diversity (generated by interspecific hybridization) in a dominant riparian tree affects an arthropod community composed of 207 species. In an experimental garden, plant cross type structured the arthropod community of individual trees, and among stands in the wild, plant genetic diversity accounted for nearly 60% of the variation in arthropod diversity. While previous experimental garden studies have demonstrated the effects of plant genotype on arthropod communities, our study extends these findings from individual trees in an experimental garden to natural stands of cottonwoods where plant population genetic diversity was a significant factor structuring arthropod diversity. These findings argue that the preservation of genetic diversity in a dominant species is far more important than previously realized, and may be particularly important in hybridizing systems.     

Adaptive mgl-regulatory mutations and genetic diversity evolving in glucose-limited Escherichia coli populations

The mutational adaptation of E. coli to low glucose concentrations was studied in chemostats over 280 generations of growth. All members of six independent populations acquired increased fitness through the acquisition of mutations at the mgl locus, increasing the binding protein-dependent transport of glucose. These mutations provided a strong fitness advantage (up to 10-fold increase in glucose affinity) and were present in most isolates after 140 generations. mgl constitutivity in some isolates was caused by base substitution, short duplication, small deletion and IS1 insertion in the 1041 bp gene encoding the repressor of the mgl system, mglD (galS). But an unexpectedly large proportion of mutations were located in the short mgl operator sequence (mglO), and the majority of mutations were in mglO after 280 generations of selection. The adaptive mglO substitutions in several independent populations were at exactly the positions conserved in the two 8 bp half-sites of the mgl operator, with the nature of the base changes also completely symmetrical. Either mutations were directed to the operator or the particular operator mutations had a selective advantage under glucose limitation. Indeed, isolates carrying mglO mutations showed greater rates of transport for glucose and galactose at low concentrations than those carrying mglD null mutations. mglO mutations avoid cross-talk by members of the GalR-Lacl repressor family, reducing transporter expression and providing a competitive advantage in a glucose-limited environment. Another interesting aspect of these results was that each adapted population acquired multiple mgl alleles, with several populations containing at least six different mgl-regulatory mutations co-existing after 200 generations. The diversity of mutations in the mglO/mglD region, generally in combination with mutations at other loci regulating glucose uptake (malT, mlc, ptsG), provided evidence for multiple clones in each population. Increased fitness was accompanied by the generation of genetic diversity and not the evolution of a single winner clone, as predicted by the periodic selection model of bacterial populations.     

濒危植物元宝山冷杉的遗传多样性研究

元宝山冷杉(Abies yuanbaoshanensis)是仅分布于广西融水县元宝山的珍稀濒危物种。本研究采用AFLP分子标记分析了元宝山冷杉种群的遗传多样性。取元宝山冷杉种群43棵植株作为研究材料,4对引物组合用于AFLP扩增,共得到261条DNA扩增带。分析结果：元宝山冷杉种群的多态位点百分比率为50．96％,Nei's基因多样性为0．1510,Shannon多样性指数为0．1735。用NTSYS软件计算各个样品间的相似性系数,并用UPGMA法基于相似性系数进行了聚类分析。研究结果表明：元宝山冷杉种群的遗传多样性水平低,种群内个体间的相似性系数很大,无明显亚种群间的遗传分化。要保护或保存这个物种的遗传资源,建议应该选择种群内尽可能多的个体进行保护。     

Isolation of Arabidopsis mutants lacking components of acquired thermotolerance

Acquired thermotolerance is a complex physiological phenomenon that enables plants to survive normally lethal temperatures. This study characterizes the temperature sensitivity of Arabidopsis using a chlorophyll accumulation bioassay, describes a procedure for selection of acquired thermotolerance mutants, and provides the physiological characterization of one mutant (AtTS02) isolated by this procedure. Exposure of etiolated Arabidopsis seedlings to 48 degrees C or 50 degrees C for 30 min blocks subsequent chlorophyll accumulation and is eventually lethal. Arabidopsis seedlings can be protected against the effects of a 50 degrees C, 30-min challenge by a 4-h pre-incubation at 38 degrees C. By the use of the milder challenge, 44 degrees C for 30 min, and protective pretreatment, mutants lacking components of the acquired thermotolerance system were isolated. Putative mutants isolated by this procedure exhibited chlorophyll accumulation levels (our measure of acquired thermotolerance) ranging from 10% to 98% of control seedling levels following pre-incubation at 38 degrees C and challenge at 50 degrees C. The induction temperatures for maximum acquired thermotolerance prior to a high temperature challenge were the same in AtTS02 and RLD seedlings, although the absolute level of chlorophyll accumulation was reduced in the mutant. Genetic analysis showed that the loss of acquired thermotolerance in AtTS02 was a recessive trait. The pattern of proteins synthesized at 25 degrees C and 38 degrees C in the RLD and AtTS02 revealed the reduction in the level of a 27-kD heat shock protein in AtTS02. Genetic analysis showed that the reduction of this protein level was correlated with the acquired thermotolerance phenotype.     

The heat shock response and acquired thermotolerance in three strains of cyanobacteria

The heat shock response of three cyanobacterial strains,Anabaena sp. Strain PCC (paris Culture Collection) 7120,Plectonema boryanum Strain PCC 6306, andSynechococcus sp. Strain PCC 7942, was characterized by polyacrylamide gel electrophoresis.Anabaena produced 33 heat shock proteins,P. boryanum 35 proteins, andSynechoccus 19 proteins. The rapid response to heat shock was consistent for all three strains, although the number of time-dependent proteins varied. All strains developed thermotolerance when first pretreated with a sublethal heat shock and then challenged with a previously lethal temperature. A 30-min 30°C incubation was required between the heat shock and challenge forSynechococcus, but not forAnabaena andP. boryanum. Synechococcus cells required a higher challenge temperature (51° vs. 49°C) than the other two strains to destroy control cells that were not pretreated with a heat shock.     

不仅仅是遗传多样性:植物保护遗传学进展

保护遗传学研究的是影响物种灭绝的遗传因素以及濒危物种的遗传管理, 以降低物种的灭绝风险。本文从遗传多样性本身及其对生态系统的影响两个方面介绍了植物保护遗传学的最新进展。根据遗传标记的功能, 保护遗传学研究可分为选择中性遗传变异研究和适应性遗传变异两个方面。对于目前主要采用的选择中性遗传标记研究, 本文着重介绍了以下方面的最新进展: (1)利用遗传标记进行个体、物种或遗传单元的鉴定, 从而有效地设计保护策略, 避免在迁地保护中混淆物种, 提高保护效率; (2)应重视由于物种自身生殖、扩散等原因造成的隐性瓶颈效应。由于选择中性遗传标记并不能准确反映物种的适应性遗传基础, 从适应性遗传变异角度研究濒危物种的进化潜力已成为保护遗传学的研究前沿。大部分相关研究还集中在利用基因组扫描检测受选择的位点, 而对功能基因的适应性研究还比较少。景观遗传学旨在解释景观和生境影响下的种群间基因流和遗传多样性格局, 这方面研究将会促进我们更多了解种群基因流的地理限制因子和不同景观基质下的种群遗传差异。遗传多样性作为物种的一种属性亦可在一定程度上反馈, 并影响生态系统。这提示我们不仅仅是濒危物种, 常见物种的遗传多样性及其保护亦很重要。最后, 我们从4个方面对保护遗传学研究进行了展望, 包括应加强将生态系统各环节联系起来研究遗传多样性, 在技术手段上利用多态性更丰富的分子标记, 同时强调了对常见物种保护遗传学研究的重要性, 并初步分析了我国保护遗传学研究与国际水平的差距, 建议加强种群遗传学和进化生物学基础理论的学习。