植物分子生物学研究极具前景的模式系统——小立碗藓

小立碗藓作为植物分子生物学研究极具前景的模式系统已日益受到人们的重视,它的生活史周期短,易于培养,转基因植株易于分析,核基因组容易和外源DNA 发生同源重组,这些特点使它成为研究基因功能的良好材料。一些成功的基因敲除和基因破坏已经在小立碗藓中实现,这些基因的功能也通过小立碗藓转化植株的特点得以证实。小立碗藓标签突变文库已经建立,其应用为小立碗藓基因的进一步研究打下了基础。关于小立碗藓的ESTs 数据库已经建立,已有67 000 条ESTs 信息。     

有前景的模式植物小立碗藓的研究新进展

小立碗藓是在分子生物学研究方面有广阔应用前景的模式植物。该文主要综述了有关小立碗藓在功能基因组学、进化和适应性及植物生理等方面最新的研究进展。     

植物分子生物学研究极具前景的模式系统--小立碗藓

小立碗藓作为植物分子生物学研究极具前景的模式系统已日益受到人们的重视,它的生活史周期短,易于培养,转基因植株易于分析,核基因组容易和外源DNA发生同源重组,这些特点使它成为研究基因功能的良好材料.一些成功的基因敲除和基因破坏已经在小立碗藓中实现,这些基因的功能也通过小立碗藓转化植株的特点得以证实.小立碗藓标签突变文库已经建立,其应用为小立碗藓基因的进一步研究打下了基础.关于小立碗藓的ESTs数据库已经建立,已有67 000条ESTs信息.     

小立碗藓萜类物质的合成酶基因分析及其UPLC-QTOF检测

根据基因组信息和KEGG数据库分析小立碗藓基因组中合成萜类物质的基因,比较小立碗藓与酵母和拟南芥合成萜类物质基因的氨基酸序列同源性同时利用UPLC-QTOF分析小立碗藓中物质组成,来分析小立碗藓基因组中萜类物质合成的基因及小立碗藓中存在的萜类物质。与酵母相比,小立碗藓两条萜类次生代谢途径完整,途径中的基因及氨基酸丰富性更高,提示可以合成更丰富的前体物质如FPP,GPP等;小立碗藓与拟南芥的序列相似性较高,萜类背景简单。UPLC-QTOF分析检测到小立碗藓中次生代谢物质主要是芳香族化合物及各类生物碱,一种萜类物质ent-16beta-Methoxy-19-kauranoic acid。小立碗藓中本身具有合成萜类前体物质和二萜的基因,检测到少量萜类物质,适合作为萜类活性物质异源合成的底盘细胞。     

Cloning and characterization of chalcone synthase from the moss, Physcomitrella patens

Since the early evolution of land plants from primitive green algae, flavonoids have played an important role as UV protective pigments in plants. Flavonoids occur in liverworts and mosses, and the first committed step in the flavonoid biosynthesis is catalyzed by chalcone synthase (CHS). Although higher plant CHSs have been extensively studied, little information is available on the enzymes from bryophytes. Here we report the cloning and characterization of CHS from the moss, Physcomitrella patens. Taking advantage of the available P. patens EST sequences, a CHS (PpCHS) was cloned from the gametophores of P. patens, and heterologously expressed in Escherichia coli. PpCHS exhibited similar kinetic properties and substrate preference profile to those of higher plant CHS. p-Coumaroyl-CoA was the most preferred substrate, suggesting that PpCHS is a naringenin chalcone producing CHS. Consistent with the evolutionary position of the moss, phylogenetic analysis placed PpCHS at the base of the plant CHS clade, next to the microorganism CHS-like gene products. Therefore, PpCHS likely represents a modern day version of one of the oldest CHSs that appeared on earth. Further, sequence analysis of the P. patens EST and genome databases revealed the presence of a CHS multigene family in the moss as well as the 3'-end heterogeneity of a CHS gene. Of the 19 putative CHS genes, 10 genes are expressed and have corresponding ESTs in the databases. A possibility of the functional divergence of the multiple CHS genes in the moss is discussed.     

苔藓植物小立碗藓，功能基因组学研究新的模式系统

苔藓植物具有相对简单的发育模式,单倍体的配子体在其生活史中占主导地位,作为研究植物生物学过程的模式系统具有诸多的优越性。苔藓植物小立碗藓能够高效地通过同源重组的方式将外源核酸整合到其核DNA,这就使得基因打靶在此物种中就像在小鼠胚胎干细胞和酵母中一样成为一个非常便利的技术。另外由于小立碗藓与高等植物在生物特征上有很大相似之处加之其有其他诸多优越性,它有望成为一个诱人的植物生物学和功能基因组学研究的模式系统。Abstract：The potential of moss as a model system to study plant biological process is associated with their relatively simple developmental pattern and the dominance of the haploid gametophyte in the life cycle. The moss Physcomitrella patens exhibits a very high rate of homologous recombination in its nuclear DNA, making gene targeting approaches in this plant as convenient as in yeast or in ES cells of mice. Sharing many biological features with higher plants and having many other advantages, the moss Physcomitrella patens will be an attractive model system for plant biology and functional genome analysis.     

Comparison of gene targeting efficiencies in two mosses suggests that it is a conserved feature of Bryophyte transformation

The moss, Physcomitrella patens, is a novel tool in plant functional genomics due to its exceptionally high gene targeting efficiency that is so far unique for plants. To determine if this high gene targeting efficiency is exclusive to P. patens or if it is a common feature to mosses, we estimated gene-targeting efficiency in another moss, Ceratodon purpureus. We transformed both mosses with replacement vectors corresponding to the adenine phosphoribosyl transferase (APT) reporter gene. We achieved a gene targeting efficiency of 20.8% for P. patens and 1.05% for C. purpureus. Our findings support the hypothesis that efficient gene targeting could be a general mechanism of Bryophyte transformation.     

Moss systems biology en route: phytohormones in Physcomitrella development

The moss Physcomitrella patens has become a powerful model system in modern plant biology. Highly standardized cell culture techniques, as well as the necessary tools for computational biology, functional genomics and proteomics have been established. Large EST collections are available and the complete moss genome will be released soon. A simple body plan and the small number of different cell types in Physcomitrella facilitate the study of developmental processes. In the filamentous juvenile moss tissue, developmental decisions rely on the differentiation of single cells. Developmental steps are controlled by distinct phytohormones and integration of environmental signals. Especially the phytohormones auxin, cytokinin, and abscisic acid have distinct effects on early moss development. In this article, we review current knowledge about phytohormone influences on early moss development in an attempt to fully unravel the complex regulatory signal transduction networks underlying the developmental decisions of single plant cells in a holistic systems biology approach.     

Exploration and identification of Physcomitrella patens moss peptides

In the current study the isolation and identification of Physcomitrella patens (Hedw.) B.S.G. moss peptides are described. Physcomitrella patens moss is actively used in recent years as a model organism to study the biology of plants. Protoplasts, protonemata and gametophores of the moss are demonstrated for the first time to contain diverse small peptides. From gametophores was isolated and identified 58 peptides that are fragments of 14 proteins, and from protonemata - 49 peptides, fragments of 15 proteins. It was found that the protonemata and gametophores Ph. patens, which are the successive stages of development of this plant, significantly different from each other as a peptide composition and the spectrum of the precursor protein of identified peptides. Isolation of protoplasts of the enzymatic destruction of cell wall protonemata accompanied by massive degradation of intracellular proteins, many of whom are proteins of photosynthesis, which is a characteristic response of plants to stress the impact of environmental factors. A total of moss protoplasts were isolated and identified 323 peptides that are fragments of 79 proteins.     

Evolutionary crossroads in developmental biology: Physcomitrella patens

The moss Physcomitrella patens has recently emerged as a powerful genetically tractable model plant system. As a member of the bryophytes, P. patens provides a unique opportunity to study the evolution of a myriad of plant traits, such as polarized cell growth, gametophyte-to-sporophyte transitions, and sperm-to-pollen transition. The availability of a complete genome sequence, together with the ability to perform gene targeting efficiently in P. patens has spurred a flurry of elegant reverse genetic studies in this plant model that address a variety of key questions in plant developmental biology.     

Efficient gene targeting in the moss Physcomitrella patens

The moss Physcomitrella patens is used as a genetic model system to study plant development, taking advantage of the fact that the haploid gametophyte dominates in its life cycle. Transformation experiments designed to target three single-copy genomic loci were performed to determine the efficiency of gene targeting in this plant. Mean transformation rates were 10-fold higher with the targeting vectors and molecular evidence for the integration of exogenous DNA into each targeted locus by homologous recombination is provided. The efficiency of gene targeting determined in these experiments is above 90%, which is in the range of that observed in yeast and several orders of magnitude higher than previous reports of gene targeting in plants. Thus, gene knock-out and allele replacement approaches are directly accessible to study plant development in the moss Physcomitrella patens . Moreover, efficient gene targeting has so far only been observed in lower eukaryotes such as protozoa, yeasts and filamentous fungi, and, as shown here the first example from the plant kingdom is a haplobiontic moss. This suggests a possible correlation between efficient gene targeting and haplo-phase in eukaryotes.     

BLADE-ON-PETIOLE genes are not involved in the transition from protonema to gametophore in the moss Physcomitrella patens

Journal of Plant Research - The timing of the transition between developmental phases is a critical determinant of plant form. In the moss Physcomitrella patens, the transition from protonema to...     

The moss bioreactor

The production of recombinant proteins in moss bioreactors provides all of the benefits of molecular farming in plants but avoids many plant-specific disadvantages, such as the genetic instability of de-differentiated cells in suspension culture or the lack of containment during field production. Protein yields are in the same range as those of other cell-culture-based production systems. On top of this, the moss Physcomitrella patens is the only known plant that can be genetically modified by homologous recombination, allowing efficient targeted gene disruption. Thus, the major drawback of producing human proteins in plants, allergic reactions caused by plant-specific glycosylation, can be diminished by targeted knockout of the responsible genes in moss. Unlike all other plants, moss allows straightforward 'humanisation' of plant-derived pharmaceuticals.     

小立碗藓（Physcomitrella patens）植物microRNA结合靶位预测

利用857条植物miRNA序列对27546条小立碗藓mRNA序列进行搜索,预测出162个植物miRNA家族在小立碗藓中存在结合靶位。miRNA结合靶位数目和miRNA协同作用网络分析结果同时显示,miR482和miR1168在小立碗藓中结合靶位多、协同作用广,提示它们对于小立碗藓可能具有重要生物学功能。52个菜茵衣藻特有的miRNA被预测在小立碗藓中存在结合靶位,显示小立碗藓在从藻类向种子植物进化过程中处在独特演化位置。     

Cryptochrome light signals control development to suppress auxin sensitivity in the moss Physcomitrella patens

The blue light receptors termed cryptochromes mediate photomorphological responses in seed plants. However, the mechanisms by which cryptochrome signals regulate plant development remain obscure. In this study, cryptochrome functions were analyzed using the moss Physcomitrella patens. This moss has recently become known as the only plant species in which gene replacement occurs at a high frequency by homologous recombination. Two cryptochrome genes were identified in Physcomitrella, and single and double disruptants of these genes were generated. Using these disruptants, it was revealed that cryptochrome signals regulate many steps in moss development, including induction of side branching on protonema and gametophore induction and development. In addition, the disruption of cryptochromes altered auxin responses, including the expression of auxin-inducible genes. Cryptochrome disruptants were more sensitive to external auxin than wild type in a blue light-specific manner, suggesting that cryptochrome light signals repress auxin signals to control plant development.     

Alpha-dioxygenases

Alpha-dioxygenases constitute a family of fatty acid-metabolizing enzymes recently discovered in plants. The present paper gives a brief overview of the literature dealing with these enzymes and additionally reports the new finding of an alpha-dioxygenase in the moss, Physcomitrella patens, and some properties of this enzyme.