Isolation of cDNA clones for genes that are expressed during leaf senescence in Brassica napus. Identification of a gene encoding a senescence-specific metallothionein-like protein.

cDNA clones representing genes that are expressed during leaf senescence in Brassica napus were identified by differential screening of a cDNA library made from RNA isolated from leaves at different stages of senescence. The expression of these genes at different stages of leaf development was examined by northern blot analysis, and several different patterns of expression were observed. One of the clones, LSC54, represented a gene that is expressed at high levels during leaf senescence. Analysis of this gene indicated strong expression in flowers as well as in senescing leaves. DNA sequence analysis of the LSC54 cDNA indicated a similarity between the deduced amino acid sequence and several metallothionein-like proteins previously identified in plants.     

水稻叶绿体蛋白质在生长发育过程中的表达研究

在植物中,叶绿体是负责光合作用的细胞器,对叶绿体内的各种生物过程人们已经积累了很多知识,但对叶绿体蛋白质的表达还所知甚少．为了解水稻叶绿体蛋白质在正常生长发育过程中的表达情况,尝试基于抗体的水稻蛋白质组学策略．选取了10个水稻叶绿体基因,利用表达的蛋白质或合成的抗原决定簇片段制备了抗体,用Western blotting检测了相应蛋白质在5个发育时期的根、茎、叶及穗组织中的表达．发现10个蛋白质均在叶片中表达,在根中不表达．与原初反应相关的叶绿素A/B结合蛋白1和2(CAB1和CAB2)、与电子传递相关的放氧增强蛋白1(OEE1)及与活性氧清除相关的过氧还蛋白过氧化物酶(2-CysP)和硫氧还蛋白(Trx)在茎中表达．而在卡尔文循环中发挥作用的Rubisco活化酶(RCA)、甘油醛-3-磷酸脱氢酶(GAPDH)、果糖二磷酸醛缩酶(FBPA)和景天庚酮糖-1, 7-二磷酸酶(SBPase)蛋白质在茎中不表达．在穗中,这些蛋白质的表达时序不同,CAB2和2-CysP在穗发育的全程表达,CAB1和OEE1在中后期表达,而卡尔文循环中的蛋白质只在中期表达．有意思的是,卡尔文循环中的蛋白质表达模式相似,这一结果从蛋白质表达水平支持它们之间的相互衔接关系．此外,实验还揭示了可能的蛋白质修饰、二聚体及不同的转录本现象．将目标基因的表达谱与转录谱进行比较,发现二者间有一定的平行性,但也有明显的区别．以水稻叶绿体蛋白质为对象,直观并相对定量地揭示了它们的表达模式,为阐释其功能提供了信息,也为基于抗体的水稻蛋白质组学策略提供了一个初步数据．     

Portrait of the expansin superfamily in Physcomitrella patens: comparisons with angiosperm expansins

BACKGROUND AND AIMS: Expansins are plant cell wall loosening proteins important in a variety of physiological processes. They comprise a large superfamily of genes consisting of four families (EXPA, EXPB, EXLA and EXLB) whose evolutionary relationships have been well characterized in angiosperms, but not in basal land plants. This work attempts to connect the expansin superfamily in bryophytes with the evolutionary history of this superfamily in angiosperms. METHODS: The expansin superfamily in Physcomitrella patens has been assembled from the Physcomitrella sequencing project data generated by the Joint Genome Institute and compared with angiosperm expansin superfamilies. Phylogenetic, motif, intron and distance analyses have been used for this purpose. KEY RESULTS: A gene superfamily is revealed that contains similar numbers of genes as found in arabidopsis, but lacking EXLA or EXLB genes. This similarity in gene numbers exists even though expansin evolution in Physcomitrella diverged from the angiosperm line approx. 400 million years ago. Phylogenetic analyses suggest that there were a minimum of two EXPA genes and one EXPB gene in the last common ancestor of angiosperms and Physcomitrella. Motif analysis seems to suggest that EXPA protein function is similar in bryophytes and angiosperms, but that EXPB function may be altered. CONCLUSIONS: The EXPA genes of Physcomitrella are likely to have maintained the same biochemical function as angiosperm expansins despite their independent evolutionary history. Changes seen at normally conserved residues in the Physcomitrella EXPB family suggest a possible change in function as one mode of evolution in this family.     

Expansins: expanding importance in plant growth and development

Expansins were originally identified as cell wall-loosening proteins. The existence and various roles of expansins have been discovered in many plants. Expansins are encoded by a superfamily of genes comprised of subfamilies that evolved from a common ancestor and encode the α-expansins (EXPAs), the β-expansins (EXPBs), the expansin-like A (EXLA), and expansin-like B (EXLB) proteins. Several expansin-like genes have also been identified in non-plant organisms (e.g. a slime mold, fungi, nematodes, and a mollusk). Localization of EXPA and EXPB in the cell wall was confirmed by immunogold electron microscopy. Studies using transgenic plants provided evidence for a broad range of biological roles of expansins in diverse aspects of plant growth and development, such as cell wall extension, fruit softening, abscission, floral organ development, symbiosis, and the response to environmental stresses.     

百脉根类LATERAL ORGAN BOUNDARIES基因的分离及表达方式

植物顶端分生组织可分为中央区,周缘区和肋区。在植物胚后发育中,侧生器官产生于顶端分生组织的周缘区。顶端分生组织和侧生器官之间的边界的建立和维持是一个非常重要的发育过程,许多调节子参与控制这个过程。拟南芥的LATERAL ORGAN BOUNDARIES（LOB）基因具有独特的表达模式,其表达的范围与上述的边界区域重合。LOB基因隶属于一个大的基因家族一,OB结构域基因家族。该家族编码的蛋白在N端具有一个保守的LOB结构域,该家族LOB基因以外的成员也参与拟南芥不同的发育过程。为了探讨在与拟南芥亲缘关系较远的豆科中LOB同源基因的功能,我们在豆科模式植物百脉根中分离了3个LOB同源基因,命名为LjLOB基因,并用RNA原位杂交方法研究了这3个基因的表达模式。研究结果显示,LjLOB1和LjLOB3都强烈地在小叶原基的基部表达,这种表达模式可能与小叶原基和复叶原基之间的边界相关。而LjLOB4则在发育中的花芽不同轮之间的边界上表达。百脉根中这3个基因具有不同的表达模式,强烈地提示它们的功能发生了分歧：LjLOB1和LjLDB3可能在复叶发育中具有重要功能;而LjLOB4则可能参与了花的发育。     

Localization of Expression of Three Cold-Induced Genes, blt101, blt4.9, and blt14, in Different Tissues of the Crown and Developing Leaves of Cold-Acclimated Cultivated Barley

Tissues expressing mRNAs of three cold-induced genes, blt101, blt14, and blt4.9, and a control gene, elongation factor 1α, were identified in the crown and immature leaves of cultivated barley (Hordeum vulgare L. cv Igri). Hardiness and tissue damage were assessed. blt101 and blt4.9 mRNAs were not detected in control plants; blt14 was expressed in control plants but only in the inner layers of the crown cortex. blt101 was expressed in many tissues of cold-acclimated plants but most strongly in the vascular-transition zone of the crown; blt14 was expressed only in the inner layers of the cortex and in cell layers partly surrounding vascular bundles in the vascular-transition zone; expression of blt4.9, which codes for a nonspecific lipid-transfer protein, was confined to the epidermis of the leaf and to the epidermis of the older parts of the crown. None of the cold-induced genes was expressed in the tunica, although the control gene was most strongly expressed there. Thus, the molecular aspects of acclimation differed markedly between tissues. Damage in the vascular-transition zone of the crown correlated closely with plant survival. Therefore, the strong expression of blt101 and blt14 in this zone may indicate a direct role in freezing tolerance of the crown.     

A spectrum of genes expressed during early stages of rice panicle and flower development

To unravel gene expression patterns during rice inflorescence development, particularly at early stages of panicle and floral organ specification, we have characterized random cloned cDNAs from developmental-stage-specific libraries. cDNA libraries were constructed from rice panicles at the stage of branching and flower primordia specification or from panicles undergoing floral organogenesis. Partial sequence analysis and expression patterns of some of these random cDNA clones from these two rice panicle libraries are presented. Sequence comparisons with known DNA sequences in databases reveal that approximately sixtyeight per cent of these expressed rice genes show varying degrees of similarity to genes in other species with assigned functions. In contrast, thirtytwo per cent represent uncharacterized genes. cDNAs reported here code for potential rice homologues of housekeeping molecules, regulators of gene expression, and signal transduction molecules. They comprise both single-copy and multicopy genes, and genes expressed differentially, both spatially and temporally, during rice plant development. New rice cDNAs requiring specific mention are those with similarity toCOP1, a regulator of photomorphogenesis inArabidopsis; sequence-specific DNA binding plant proteins like AP2-domain-containing factors; genes that specify positional information in shoot meristems like leucine-rich-repeat-containing receptor kinases; regulators of chromatin structure like Polycomb domain protein; and also proteins induced by abiotic stresses.     

The embryonic expression patterns of zebrafish genes encoding LysM-domains

The function and structure of LysM-domain containing proteins are very diverse. Although some LysM domains are able to bind peptidoglycan or chitin type carbohydrates in bacteria, in fungi and in plants, the function(s) of vertebrate LysM domains and proteins remains largely unknown. In this study we have identified and annotated the six zebrafish genes of this family, which encode at least ten conceptual LysM-domain containing proteins. Two distinct sub-families called LysMD and OXR were identified and shown to be highly conserved across vertebrates. The detailed characterization of LysMD and OXR gene expression in zebrafish embryos showed that all the members of these sub-families are strongly expressed maternally and zygotically from the earliest stages of a vertebrate embryonic development. Moreover, the analysis of the spatio-temporal expression patterns, by whole mount and fluorescent in situ hybridizations, demonstrates pronounced LysMD and OXR gene expression in the zebrafish brain and nervous system during stages of larval development. None of the zebrafish LysMD or OXR genes was responsive to challenge with bacterial pathogens in embryo models of Salmonella and Mycobacterium infections. In addition, the expression patterns of the OXR genes were mapped in a zebrafish brain atlas.     

花生MYB转录因子的鉴定与生物信息学分析

MYB转录因子是植物中重要的基因家族之一,参与多种生物学功能的调控.目前对花生(Arachis hypogaea)MYB转录因子家族的功能仍知之甚少,对花生中MYB转录因子的鉴定及生物信息学分析具有重要的意义.本研究在栽培花生中共鉴定出MYB转录因子443个,包括219个1R-MYB、209个2R-MYB、12个3R-...     

Expression of var genes located within polymorphic subtelomeric domains of Plasmodium falciparum chromosomes.

Plasmodium falciparum var genes encode a diverse family of proteins, located on the surfaces of infected erythrocytes, which are implicated in the pathology of human malaria through antigenic variation and adhesion of infected erythrocytes to the microvasculature. We have constructed a complete representative telomere-to-telomere yeast artificial chromosome (YAC) contig map of the P. falciparum chromosome 8 for studies on the chromosomal organization, distribution, and expression of var genes. Three var gene loci were identified on chromosome 8, two of which map close to the telomeres at either end of the chromosome. Analysis of the previously described chromosome 2 contig map and random P. falciparum telomeric YAC clones revealed that most, if not all, 14 P. falciparum chromosomes contain var genes in a subtelomeric location. Mapping the chromosomal location of var genes expressed in a long-term culture of the P. falciparum isolate Dd2 revealed that four of the five different expressed var genes identified map within subtelomeric locations. Expression of var genes from a chromosomal domain known for frequent rearrangements has important implications for the mechanism of var gene switching and the generation of novel antigenic and adhesive phenotypes.     

Kunitz trypsin inhibitor genes are differentially expressed during the soybean life cycle and in transformed tobacco plants.

We investigated the structure, organization, and developmental regulation of soybean Kunitz trypsin inhibitor genes. The Kunitz trypsin inhibitor gene family contains at least 10 members, many of which are closely linked in tandem pairs. Three Kunitz trypsin inhibitor genes, designated as KTi1, KTi2, and KTi3, do not contain intervening sequences, and are expressed during embryogenesis and in the mature plant. The KTi1 and KTi2 genes have nearly identical nucleotide sequences, are expressed at different levels during embryogenesis, are represented in leaf, root, and stem mRNAs, and probably do not encode proteins with trypsin inhibitor activity. By contrast, the KTi3 gene has diverged 20% from the KTi1 and KTi2 genes, and encodes the prominent Kunitz trypsin inhibitor found in soybean seeds. The KTi3 gene has the highest expression level during embryogenesis, and is also represented in leaf mRNA. All three Kunitz trypsin inhibitor genes are regulated correctly in transformed tobacco plants. Our results suggest that Kunitz trypsin inhibitor genes contain different combinations of cis-control elements that program distinct qualitative and quantitative expression patterns during the soybean life cycle.