颈卵器植物MADS-box基因的研究进展

作者通过对颈卵器植物MADS_box基因最新研究结果的概述 ,介绍了MADS_box基因与颈卵器植物生殖器官决定、发育和进化的关系以及被子植物花器官发育的ABCD模型在三类颈卵器植物中的表现形式和进化关系。这些结果表明MADS_box基因的结构、功能和表达模式的变化是植物生殖器官决定、发育和进化的主要原因。     

喀斯特山顶区域濒危裸子植物群落特征及其地形关联

喀斯特濒危裸子植物往往局限分布于生境恶劣的山顶区域,受保护的急迫性和必要性较强,但目前针对该区植物群落的研究较少,保护技术措施缺乏理论支持。对木论喀斯特山顶区域典型的濒危裸子植物群落进行了调查,分析了该群落特征的空间变异及其地形关联。结果表明：该群落共有植物73种,隶属于39科58属;裸子植物、双子叶植物、单子叶植物分别有3、67、3种;壳斗科、蔷薇科和樟科物种相对较多;64.1%的科和81.0%的属只含有1个物种。双子叶植物净关系指数（NRI）和最近关系指数（NTI）表现出随机格局。个体数、总基面积、NTI分别在5.66、4.75、6.51 m尺度内具有强烈的空间相关性,空间连续性相对较差;Shannon多样性指数、Simpson多样性指数、Pielou均匀度指数分别在71.01、71.01、42.44 m尺度内具有强烈的空间相关性,空间连续性相对较好。总基面积与凹凸度呈显著正相关关系;濒危裸子植物相对基面积与坡度呈显著正相关关系;NTI与相对海拔呈极显著正相关关系,与坡度和坡向均呈显著负相关关系。上述结果对于喀斯特濒危裸子植物的保护和恢复工作具有一定的指导意义。     

Envelope-Like Retrotransposons in the Plant Kingdom: Evidence of Their Presence in Gymnosperms (Pinus pinaster)

Retroviruses differ from retrotransposons due to their infective capacity, which depends critically on the encoded envelope. Some plant retroelements contain domains reminiscent of the env of animal retroviruses but the number of such elements described to date is restricted to angiosperms. We show here the first evidence of the presence of putative env-like gene sequences in a gymnosperm species, Pinus pinaster (maritime pine). Using a degenerate primer approach for conserved domains of RNaseH gene, three clones from putative envelope-like retrotransposons (PpRT2, PpRT3, and PpRT4) were identified. The env-like sequences of P. pinaster clones are predicted to encode proteins with transmembrane domains. These sequences showed identity scores of up to 30% with env-like sequences belonging to different organisms. A phylogenetic analysis based on protein alignment of deduced aminoacid sequences revealed that these clones clustered with env-containing plant retrotransposons, as well as with retrotransposons from invertebrate organisms. The differences found among the sequences of maritime pine clones isolated here suggest the existence of different putative classes of env-like retroelements. The identification for the first time of env-like genes in a gymnosperm species may support the ancestrality of retroviruses among plants shedding light on their role in plant evolution.     

神农架世界自然遗产地种子植物科属的古老性

为了研究神农架世界自然遗产地的种子植物区系特征,基于Phylomatic建立时间树并综合多学科证据,探讨了该区系种子植物科属起源的时间特征。结果发现,神农架世界自然遗产地裸子植物占中国华中山地分布中心属和种的67%和74%,是中国裸子植物分布中心之一;被子植物科的基部类群科占中国的85%;种子植物单型科（仅含1属1种）占中国的42%;拥有中国特有属56属,占中国特有属总数的23%,很多为古老特有属;神农架世界自然遗产地还分布有中国超过50%的东亚-北美间断分布属。这些事实表明神农架世界自然遗产地种子植物区系起源古老,且有连续的传代线,是神农架世界自然遗产地突出普遍价值的重要体现。     

Distinct MADS-box gene expression patterns in the reproductive cones of the gymnosperm<Emphasis Type="Italic"> Gnetum gnemon</Emphasis>

Expression patterns from in situ hybridization of four MADS-box genes (GGM7, GGM9, GGM11, and GGM15) from the gymnosperm species Gnetum gnemon are presented. Together with previously published data about putative orthologs of floral homeotic genes from G. gnemon (GGM2, GGM3, GGM13), we describe seven temporally and spatially distinct expression patterns in male, female or both types of reproductive units which very likely reflect the diversity of MADS-box gene function in gymnosperm cones. There is evidence that some aspects of the observed differential expression have been conserved since the last common ancestor of extant angiosperms and gymnosperms about 300 million years ago.Edited by R.J. Sommer     

Characterization of the structure,expression and function of <Emphasis Type="Italic">Pinus radiata</Emphasis> D. Don arabinogalactan-proteins

A synthetic phenylglycoside (beta-GlcY) that interacts specifically with arabinogalactan-proteins (AGPs), a class of plant cell surface proteoglycans, has been used to study the spatial distribution of AGPs in the xylem tissue of radiata pine. These studies demonstrated that AGPs were located in the compound middle lamella (CML) of the newly developed tracheid. Abundant, low salt extractable AGPs were purified from xylem tissue. Monosaccharide analysis showed that arabinose and galactose were the main sugars present. Linkage analysis showed that most of the arabinose was in the furanose form, at the terminal and 5-linked positions, and the majority of the galactose was in the pyranose form at the terminal 3-, 6- and 3,6-linked positions; a linkage composition typical of AGPs. The AGPs had an abundance of characteristic amino acid residues including alanine, hydroxyproline, proline, and serine. Separation of the AGPs using reversed-phase high performance liquid chromatography showed that one main fraction was eluted, which tested positive for AGPs by dot-blot analysis using anti-AGP monoclonal antibodies. Sedimentation equilibrium analysis showed that this main fraction contained a 226 kDa species. We have examined the function of AGPs in tracheid differentiation using an established radiata pine callus culture system grown on media containing beta-GlcY. The effect of beta-GlcY on the cultures was to reduce the overall tracheid differentiation rate in a concentration dependent manner, ultimately resulting in cell death. These studies provide further evidence that AGPs play an important role in tracheid differentiation, and thus may be an important biological target for improving wood quality.     

Somatic Embryogenesis and Plantlet Formation of Picea wilsonii Mast. in Ditterent Conditions

Embryogenic callus (translucent callus) was produced from immature zygotic embryos of Picea wilsonii Mast. Subsequently somatic embryogenesis occurred on the brown callus. The somatic embryos could be stimulated to developinto plantlets on the medium without hormone. Young somatic embryos were produced from embryogenic callus in liquid suspension culture, in which suspensor was several or more than ten times the size of the somatic embryo. The somatic embryo showed very similar to zygotic embryos in micro-section and living material.     

Karyotype analysis reveals interspecific differentiation in the genus Cedrus despite genome size and base composition constancy

The DNA content and GC% of the four true cedar (Cedrus) species, C. atlantica, C. brevifolia, C. deodara and C. libani, were assessed. Genome size was homogeneous among representative populations of the four species with an average of 32.6±0.6 pg per 2 C or 15.7×10⁹ base pairs per 1 C. The composition in GC was calculated to be 40.7%. A simple monosomatic haploid level was found in the megagametophyte, as compared to the diploid level of the corresponding embryo. Cytogenetic studies showed a diploid chromosome number of 2n=2x=24 in 11 populations sampled over the four species. The chromosome complements have similar morphology and symmetry. However, fluorochromes revealed specific banding patterns in each of the four cedar species. Eight GC-rich chromomycin A₃ bands were observed in Cedrus deodara chromosomes, six in both Cedrus libani and Cedrus brevifolia, and four bands in Cedrus atlantica chromosomes. Moreover, Hoechst 33258 fluorochrome revealed AT-rich sequences specifically located in the centromeric regions while the GC-rich sequences appeared negatively stained. These investigations provide a systematic characterisation of the Cedrus genus and should contribute towards clarification of the phylogenetic relationships among the four species. Received: 10 October 2000 / Accepted: 20 March 2001     

甘肃省麦积山景区3种典型裸子植物土壤微生物群落结构分析

【目的】探明不同种类的植物对其根际土壤微生物数量分布与群落结构的影响。【方法】将微生物计数法与磷脂脂肪酸(PLFA)法相结合,分析比较麦积山景区3种典型裸子植物根际土壤微生物的数量分布和PLFA种类、含量及主成分结构。【结果】3种植物根际土壤微生物数量均以细菌最多,真菌最少;总PLFA含量以红豆杉[Taxus chinensis(Pilg)Rehder.]最高、种类最多,日本落叶松[Larix kaempferi(Lamb)Carriere.]最低,红豆杉与云杉(Picea asperata Mast)PLFA主要成分相似度高于日本落叶松;外来种日本落叶松无论微生物数量,还是种类以及PLFA结构组成与红豆杉、云杉均有较大的差异,多样性显著下降。【结论】与土著裸子植物相比,外来种日本落叶松能明显改变根际土壤微生物数量分布与群落结构。