Gene structure,phylogeny and expression profile of the sucrose synthase gene family in cacao (Theobroma cacao L.)

Journal of Genetics - In higher plants, sucrose synthase (Sus, EC 2.4.1.13) is widely considered as a key enzyme involved in sucrose metabolism. Although, several paralogous genes encoding...     

The plant glutathione transferase gene family: genomic structure, functions, expression and evolution

Glutathione transferases (GSTs) are ubiquitous, multifunctional proteins encoded by large gene families. In different plant species this gene family is comprised of 25–60 members, that can be grouped into six classes on the basis of sequence identity, gene organization and active site residues in the protein. The Phi and Tau classes are the most represented and are plant specific, while Zeta and Theta GSTs are found also in animals. Despite pronounced sequence and functional diversification, GSTs have maintained a highly conserved three-dimensional structure through evolution. Most GSTs are cytosolic and active as dimers, performing diverse catalytic as well as non-catalytic roles in detoxification of xenobiotics, prevention of oxidative damage and endogenous metabolism. Among their catalytic activities are the conjugation of electrophilic substrates to glutathione, glutathione-dependent isomerizations and reductions of toxic organic hydroperoxides. Their main non-catalytic role is as hormone and flavonoid ligandins. GST genes are predominantly organized in clusters non-randomly distributed in the genome. Phylogenetic studies indicate that plant GSTs have mainly evolved after the divergence of plants, the two prevalent Phi and Tau classes being the result of recent, multiple duplication events.     

Analysis of the sucrose synthase gene family in Arabidopsis

The properties and expression patterns of the six isoforms of sucrose synthase in Arabidopsis are described, and their functions are explored through analysis of T-DNA insertion mutants. The isoforms have generally similar kinetic properties. Although there is variation in sensitivity to substrate inhibition by fructose this is unlikely to be of major physiological significance. No two isoforms have the same spatial and temporal expression patterns. Some are highly expressed in specific locations, whereas others are more generally expressed. More than one isoform is expressed in all organs examined. Mutant plants lacking individual isoforms have no obvious growth phenotypes, and are not significantly different from wild-type plants in starch, sugar and cellulose content, seed weight or seed composition under the growth conditions employed. Double mutants lacking the pairs of similar isoforms sus2 and sus3, and sus5 and sus6, are also not significantly different in these respects from wild-type plants. These results are surprising in the light of the marked phenotypes observed when individual isoforms are eliminated in crop plants including pea, maize, potato and cotton. A sus1/sus4 double mutant grows normally in well-aerated conditions, but shows marked growth retardation and accumulation of sugars when roots are subjected to hypoxia. The sucrose synthase activity in roots of this mutant is 3% or less of wild-type activity. Thus under well-aerated conditions sucrose mobilization in the root can proceed almost entirely via invertases without obvious detriment to the plant, but under hypoxia there is a specific requirement for sucrose synthase activity.     

The mammalian PYHIN gene family: Phylogeny, evolution and expression

ABSTRACT: BACKGROUND: Proteins of the mammalian PYHIN (IFI200/HIN-200) family are involved in defence against infection through recognition of foreign DNA. The family member absent in melanoma 2 (AIM2) binds cytosolic DNA via its HIN domain and initiates inflammasome formation via its pyrin domain. AIM2 lies within a cluster of related genes, many of which are uncharacterised in mouse. To better understand the evolution, orthology and function of these genes, we have documented the range of PYHIN genes present in representative mammalian species, and undertaken phylogenetic and expression analyses. RESULTS: No PYHIN genes are evident in non-mammals or monotremes, with a single member found in each of three marsupial genomes. Placental mammals show variable family expansions, from one gene in cow to four in human and 14 in mouse. A single HIN domain appears to have evolved in the common ancestor of marsupials and placental mammals, and duplicated to give rise to three distinct forms (HIN-A, -B and -C) in the placental mammal ancestor. Phylogenetic analyses showed that AIM2 HIN-C and pyrin domains clearly diverge from the rest of the family, and it is the only PYHIN protein with orthology across many species. Interestingly, although AIM2 is important in defence against some bacteria and viruses in mice, AIM2 is a pseudogene in cow, sheep, llama, dolphin, dog and elephant. The other 13 mouse genes have arisen by duplication and rearrangement within the lineage, which has allowed some diversification in expression patterns. CONCLUSIONS: The role of AIM2 in forming the inflammasome is relatively well understood, but molecular interactions of other PYHIN proteins involved in defence against foreign DNA remain to be defined. The non-AIM2 PYHIN protein sequences are very distinct from AIM2, suggesting they vary in effector mechanism in response to foreign DNA, and may bind different DNA structures. The PYHIN family has highly varied gene composition between mammalian species due to lineage-specific duplication and loss, which probably indicates different adaptations for fighting infectious disease. Non-genomic DNA can indicate infection, or a mutagenic threat. We hypothesise that defence of the genome against endogenous retroelements has been an additional evolutionary driver for PYHIN proteins.     

The myrosinase gene family in Arabidopsis thaliana: gene organization,expression and evolution

Myrosinase (thioglucoside glucohydrolase, EC 3.2.3.1.) is in Brassicaceae species such as Brassica napus and Sinapis alba encoded by two differentially expressed gene families, MA and MB, consisting of about 4 and 10 genes, respectively. Southern blot analysis showed that Arabidopsis thaliana contains three myrosinase genes. These genes were isolated from a genomic library and two of them, TGG1 and TGG2, were sequenced. They were found to be located in an inverted mode with their 3 ends 4.4 kb apart. Their organization was highly conserved with 12 exons and 11 short introns. Comparison of nucleotide sequences of TGG1 and TGG2 exons revealed an overall 75% similarity. In contrast, the overall nucleotide sequence similarity in introns was only 42%. In intron 1 the unusual 5 splice border GC was used. Phylogenetic analyses using both distance matrix and parsimony programs suggested that the Arabidopsis genes could not be grouped with either MA or MB genes. Consequently, these two gene families arose only after Arabidopsis had diverged from the other Brassicaceae species. In situ hybridization experiments showed that TGG1 and TGG2 expressing cells are present in leaf, sepal, petal, and gynoecium. In developing seeds, a few cells reacting with the TGG1 probe, but not with the TGG2 probe, were found indicating a partly different expression of these genes.     

RNA干涉AtSUS3影响拟南芥SUS家族表达模式及角果成熟

蔗糖合成酶（SuSy）是植物蔗糖代谢的关键酶,在植物生长发育过程中起着重要作用.为研究拟南芥中SUS3的功能,构建RNAi-SUS3干涉载体,通过农杆菌介导的真空渗透法转化拟南芥.筛选获得纯系转基因植株后,对AtSUS家族进行表达分析,利用环境扫描电子显微镜观察转基因植株表型,并对转基因拟南芥角果进行木质素组织化学染色以及透射电子显微镜检测.结果表明,RNA干涉技术能够抑制AtSUS3的表达,正常培养条件下该基因沉默后对拟南芥的表型没有显著影响,但可引起角果中AtSUS1,AtSUS2和AtSUS4表达代偿性增加,使转基因植株角果内果皮层细胞次生细胞壁增厚,木质化程度加深,同时果瓣厚度也有增加趋势.结果提示,转基因拟南芥角果的发育较野生型植株更为优先,AtSUS3基因沉默可能有利于角果的成熟.     

The identification and characterisation of alleles of sucrose phosphate synthase gene family III in sugarcane

Little is known about the extent of allelic diversity of genes in the complex polyploid, sugarcane. Using sucrose phosphate synthase (SPS) Gene (SPS) Family III as an example, we have amplified and sequenced a 400 nt region from this gene from two sugarcane lines that are parents of a mapping population. Ten single nucleotide polymorphisms (SNPs) were identified within the 400 nt region of which seven were present in both lines. In the elite commercial cultivar Q165^A, 10 sequence haplotypes were identified, with four haplotypes recovered at 9% or greater frequency. Based on SNP presence, two clusters of haplotypes were observed. In IJ76-514, a Saccharum officinarum accession, 8 haplotypes were identified with 4 haplotypes recovered at 13% or greater frequency. Again, two clusters of haplotypes were observed. The results suggest that there may be two SPS Gene Family III genes per genome in sugarcane, each with different numbers of different alleles. This suggestion is supported by sequencing results in an elite parental sorghum line, 403463-2-1, in which 4 haplotypes, corresponding to two broad types, were also identified. Primers were designed to the sugarcane SNPs and screened over bulked DNA from high and low Sucrose-containing progeny from a cross between Q165^A and IJ76-514. The SNP frequency did not vary in the two bulked DNA samples, suggesting that these SNPs from this SPS gene family are not associated with variation in sucrose content. Using an ecotilling approach, two of the SPS Gene Family III haplotypes were mapped to two different linkage groups in homology group 1 in Q165^A. Both haplotypes mapped near QTLs for increased sucrose content but were not themselves associated with any sugar-related trait.     

白及蔗糖合成酶基因的克隆及表达分析

为揭示白及蔗糖合成酶基因与生长发育的关系,该研究以白及为材料,利用RT-PCR技术同源克隆白及蔗糖合成酶的关键基因SuSy,对SuSy基因的生物学特性及表达特征进行了分析,并利用实时荧光定量PCR检测SuSy基因在不同组织中的表达规律。结果表明:(1)白及SuSy基因长度为2 215 bp,编码737个氨基酸,与铁皮石斛、文心兰和蝴蝶兰的蛋白质氨基酸序列的相似性分别为97%、92%和95%。(2)生物信息学分析表明,SuSy蛋白质序列具有较高的亲水性,与拟南芥SuSy蛋白质氨基酸三级结构一致性为75.2%;系统进化树分析发现,白及SuSy蛋白与铁皮石斛处于同一个分支上。(3) qRT-PCR结果表明,SuSy基因在叶片中的表达量最高,块茎中的表达量最低;成熟叶片的表达量高于未成熟叶片的表达量;数据差异性分析显示,SuSy基因在根、块茎中表达量具有极显著性差异,但在一年生叶和二年生叶中的表达量无显著性差异,幼苗叶和一、二年生叶中表达量具有极显著性差异。由此推测,SuSy基因可能受生长发育的诱导,是调控白及生长发育关键基因。     

Plant enolase: gene structure, expression, and evolution.

Enolase genes were cloned from tomato and Arabidopsis. Comparison of their primary structures with other enolases revealed a remarkable degree of conservation, except for the presence of an insertion of 5 amino acids unique to plant enolases. Expression of the enolase genes was studied under various conditions. Under normal growth conditions, steady-state messenger and enzyme activity levels were significantly higher in roots than in green tissue. Large inductions of mRNA, accompanied by a moderate increase in enzyme activity, were obtained by an artificial ripening treatment in tomato fruits. However, there was little effect of anaerobiosis on the abundance of enolase messenger. In heat shock conditions, no induction of enolase mRNA was observed. We also present evidence that, at least in Arabidopsis, the hypothesis that there exists a complete set of glycolytic enzymes in the chloroplast is not valid, and we propose instead the occurrence of a substrate shuttle in Arabidopsis chloroplasts for termination of the glycolytic cycle.     

The actin multigene family in Populus: organization, expression and phylogenetic analysis

Despite the significance of actin in plant growth and development, little is known of the structure, expression and evolution of the actin gene family in woody plants. In this study, we systematically examined the diversification of the actin gene family in Populus by integrating genomic organization, expression, and phylogeny data. Genome-wide analysis of the Populus genome indicated that actin is a multigene family consisting of eight members, all predicted to encode 377-amino acid polypeptides that share high sequence homology ranging from 94.2 to 100% identity. Microarray and real-time PCR expression analysis showed that the PtrACT family members are differentially expressed in different tissues, exhibiting overlapping and unique expression patterns. Of particular interest, all PtrACT genes have been found to be preferentially expressed in the stem phloem and xylem, suggesting that poplar PtrACTs are involved in the wood formation. Gene structural and phylogenetic analyses revealed that the PtrACT family is composed of two main subgroups that share an ancient common ancestor. Extremely high intraspecies synonymous nucleotide diversity of π_syn = 0.01205 was detected, and the π_non-syn/π_syn ratio was significantly less than 1; therefore, the PtACT1 appears to be evolving in Populus, primarily under purifying selection. We demonstrated that the actin gene family in Populus is divided into two distinct subgroups, suggesting functional divergence. The results reported here will be useful in conducting future functional genomics studies to understand the detailed function of actin genes in tree growth and development.