植物细胞壁扩展蛋白(Expansins)研究进展

Expansins(EXP)是一类植物细胞壁蛋白,它能诱导分离细胞壁的延伸生长及依赖pH调节的细胞扩展生长。在生长的组织中,细胞壁若要打破约束而扩展体积,必须取决于胞壁的生物合成与维持结构完整性及强度的壁松弛协调机制。Expansins的生物学作用是多样化的。它参与了细胞增大,果实软化,花粉管及根系生长以及植物细胞衰老等过程。现已发现两大类expansins基因家族,称之为α-expansin和β-expansin,它们都是由多基因家族组成。本文对EXP的发现,基因家族分类及其在植物发育、生长及衰老各阶段的生理作用机制等研究进展进行了综述;并对EXP的应用前景给予一定阐述。

Genome-wide analysis of expansins and their role in fruit spine development in cucumber(Cucumis sativus L.)

Cucumber is one of the most widely consumed vegetables worldwide,and the fruit spine is an important fruit quality trait.Expansins play critical roles in fruit development;however,the regulation of expansins in cucumber fruit spine development has not been reported.In this study,33 expansin genes were identified in the cucumber genome V3;additionally,expansin genes in Citrullus lanatus,Cucumis melo,Cucurbita maxima,Lagenaria siceraria,and Benincasa hispida were also identified.Phylogenetic analysis of expansin proteins in Cucurbitaceae and Arabidopsis showed that they evolved separately in each plant species.Phylogenetic analysis showed that C.maxima was derived earlier than the other five Cucurbitaceae species.The expression of CsEXPA2,CsEXPA14,and CsEXLA3 varied in cucumber lines with different fruit spine densities.A yeast two-hybrid assay showed that a putative auxin transporter encoded by numerous spine gene(ns)interacts with CsEXLA2,which may be involved in the development of the numerous spines in cucumber.These results provide novel insights into the expansins related to plant development and fruit spine development in cucumber.

Isolation and Analysis of Expansins from the Gossypium barbadense Cotton Elongating Fiber

Gossypium barbadense L.is one of the most valuable cotton species due to its silkiness,luster,long staple,and high strength.Transferring the excellent fiber traits from G.barbadense as the secondary gene pool to the widely cultivated G.hirsutum via traditional and molecular-aided selection

Abiotic stress treatment reveals expansin like A gene OfEXLA1 improving salt and drought tolerance of Osmanthus fragrans by responding to abscisic acid

Sweet osmanthus(Osmanthus fragrans) is a having general approval aromatic tree in China that is widely applied to landscaping and gardening. However, the evergreen tree adaptability is limited by many environmental stresses. Currently, limited information is available regarding the genetic analysis and functional identification of expansin genes in response to abiotic stress in sweet osmanthus. In this study, a total of 29 expansin genes were identified and divided into four groups by genome-wide analysis from the sweet osmanthus genome. Transcriptome and quantitative Real-time PCR analysis showed that the cell wall-localized protein expansin-like A(OfEXLA1) gene was significantly induced by salt and drought treatment. Histochemical GUS staining of transgenic Arabidopsis lines in which GUS activity was driven with the OfEXLA1 promoter, GUS activity was significantly induced by salt, drought, and exogenous abscisic acid(ABA). In yeast, we found OfEXLA1overexpression significantly improved the population of cells compared with wild-type strains after NaCl and polyethylene glycol(PEG)treatment. Additionally, OfEXLA1 overexpression not only promoted plant growth, but also improved the salt and drought tolerance in Arabidopsis. To gain insight into the role of ABA signaling in the regulation of OfEXLA1 improving abiotic tolerance in sweet osmanthus, four differentially expressed ABA Insensitive 5(ABI5)-like genes(OfABL4, OfABL5, OfABL7, and OfABL8) were identified from transcriptome, and dualluciferase(dual-LUC) and yeast one hybrid(Y1H) assay showed that OfABL4 and OfABL5 might bind to OfEXLA1 promoter to accumulate the OfEXLA1 expression by responding to ABA signaling to improve abiotic tolerance in sweet osmanthus. These results provide the information for understanding the molecular functions of expansin-like A gene and molecular breeding of sweet osmanthus in future.

苎麻expansin家族成员鉴定与表达分析

苎麻是一种重要的纤维作物,纤维被用作纺织工业的原料。扩展蛋白具有诱导依赖pH的细胞壁伸长和压力松弛的特性。为了对苎麻基因组中expansin家族成员数量和类型进行鉴定,并研究在纤维细度不同的苎麻茎皮中扩展蛋白基因的表达情况,研究首先在苎麻中苎1号基因组数据库挖掘到24个扩展蛋白基因家族成员,通过生物信息学方法对其分子量、等电点、信号肽、亚细胞定位、motif及基因结构进行分析和预测。系统进化树结果显示:扩展蛋白包括α亚族成员17个、β亚族4个、α类亚族1个和β类亚族2个,共分为3类;expansin家族同一进化支蛋白结构域比较保守且有一个特有的motif。然后,利用苎麻茎皮扩展蛋白基因家族成员转录组表达分析和qRT-PCR验证,发现两个基因在两个纤维细度差异显著的品种及其5个不同生长期表达量差异显著。该结果有助于了解苎麻expansin家族的进化,为影响苎麻纤维发育和纤维细度相关基因及其功能的研究奠定基础。

乙酰水杨酸调控猕猴桃果实后熟软化进程中的Ad-EXP1基因表达

以布鲁诺猕猴桃(Actinidia deliciosa cv.Bruno)成熟果实为材料,根据植物α-expansin(EXP)基因的氨基酸保守序列设计简并引物,利用RT-PCR方法结合3’RACE扩增得到1个长为957bp的cDNA片段(Ad-EXP1)。该基因片段编码211个氨基酸,与其它植物该基因核苷酸同源性为59%～85%,氨基酸同源性为73%～91%。Northern杂交结果表明,Ad-EXP1基因在采收当天的果实中表达很弱,随着果实成熟衰老进程加快趋于增强;乙酰水杨酸(ASA)处理延缓果实后熟软化和乙烯生成,也显著抑制Ad-EXP1基因表达。鉴于Ad-EXP1表达丰度与乙烯生成、果实软化程度的一致性,推测该基因在猕猴桃果实后熟软化进程中起着重要作用。

低温条件下相关关键酶活性对棉纤维比强度形成的影响

【目的】研究低温对纤维比强度形成的影响。【方法】通过设置大田分期播种试验,使相同果枝部位棉铃可以处于不同的温度条件下发育,研究低温对棉纤维发育关键酶活性及相关基因表达的影响。【结果】低温影响纤维素的累积速率并最终影响纤维比强度的形成,其原因是在不同水平上影响了纤维发育关键酶的活性。在生化水平上,低温(铃龄0～50d日均温<23.0℃,铃龄25～50d日均温<21.0℃)提高了纤维中β-1,3-葡聚糖酶的活性、降低了蔗糖合成酶的活性,且前者对温度更为敏感。在基因表达水平上,低温使Expansin、蔗糖合成酶基因的表达量增加,β-1,3-葡聚糖酶基因的表达与此相反,低温下Expansin到达表达峰值时间推后且维持高表达的时间延长,低温可导致15d铃龄纤维β-1,3-葡聚糖酶基因表达量显著降低,而蔗糖合成酶基因表达量显著升高。【结论】在纤维品质形成上,低温导致棉纤维伸长期及伸长高峰推后,低温下纤维素累积量、纤维比强度的变化特征与纤维蔗糖合成酶活性及β-1,3-葡聚糖酶基因表达的变化特征高度一致,与β-1,3-葡聚糖酶活性及蔗糖合成酶基因表达受低温影响的规律相反。

植物细胞壁松弛因子——Expansin研究进展

就Expansin的发现与来源、基因家族分类与基因结构、功能、作用机理等方面展开论述,旨在让人们系统地了解Expansin的研究进展,并为未来通过调控Expansin的表达来调控植物的生长发育、提高作物产量、延长贮藏时间等生产应用提供参考。

桃EXPANSIN基因家族序列特征及其在根结线虫侵染后的诱导表达分析

【目的】探索扩张蛋白(EXPANSIN)基因家族在桃抗南方根结线虫过程中的作用。【方法】首先对桃基因组中的EXPANSIN基因家族进行生物信息学分析,然后利用转录组测序对EXPANSIN基因在南方根结线虫侵染免疫型(‘红根甘肃桃1号’)和高感型(‘贝蕾’)桃种质根系后的不同时期的表达丰度进行分析。【结果】桃EXPANSIN基因家族有27个成员,这些成员分布在8条染色体上,以第2和第5号染色体上最多,均为5个。基因结构分析显示,这些基因包含1~5个外显子,大部分EXPANSIN基因包含DPBB_1和Pollen_allerg_1保守结构域,聚类分析将这27个成员分为2大类,其中有8个与拟南芥中已注释的与线虫侵染过程中巨细胞形成有关的蛋白质聚在一起,均属于EXPA亚类。转录组分析表明,这8个EXPANSIN基因在对南方根结线虫免疫和高感2种种质不同时期的表达趋势存在明显差异,其中ppa010314m、ppa010226m在‘贝蕾’中表达量随侵染上调,而在‘红根甘肃桃1号’中上调不明显,这2个基因可能是参与南方根结线虫侵染过程中巨细胞形成的关键基因。【结论】桃EXPANSIN家族成员在结构上高度保守,其中多个成员可能参与调控桃抗南方根结线虫过程。

Expansin超级家族的进化与命名

综述了expansin基因家族的命名法和进化研究的最新进展,介绍了expansin超级家族的发现过程和定义,分析了其基因结构和进化状况,详述了expansin这个超级家族成员的命名法则。

基于转录组的三月李及其红肉突变体Expansin基因家族鉴定及分析

【目的】Expansin是广泛存在于植物中的一类细胞壁蛋白,通过调节细胞壁柔韧性在植物生长发育过程中发挥作用。本研究旨在分析Expansin基因家族特征及其在果实成熟过程中的表达模式,并比较Expansin基因在三月李及其红肉突变体之间的差异表达。【方法】基于三月李及其红肉突变体果实成熟过程的转录组数据,采用生物信息学分析方法进行Expansin家族基因鉴定与分析。【结果】鉴定出33个李Expansin基因家族成员,编码蛋白长度在176~460 aa,分子量在19.21~51.33 kD,等电点4.62~9.83,大部分为位于细胞外的稳定亲水蛋白。系统进化树分析表明李Expansin家族成员可分为4个组:22个EXPA、6个EXPB、1个EXPLA和4个EXPLB。所有李Expansin蛋白质均具有保守的DPBB1和Pollenallerg1结构域。保守基序分析表明,同一组Expansin成员具有相似的基序组成。9个Expansin基因在三月李及其红肉突变体果实成熟过程中差异表达。【结论】Expansin在三月李及其红肉突变体果实成熟过程中的表达模式存在显著差异。本研究结果可为解析李Expansin家族基因在果实成熟过程中的功能奠定基础。

7个PcEXPA基因在茌梨和黄金梨果实采后贮藏的表达调控研究

以茌梨和黄金梨果实为试材,研究了采后贮藏期间梨果实的硬度、乙烯释放速率、可溶性果胶含量以及7个PcEXPA基因的表达模式。结果表明,茌梨和黄金梨果实硬度在采后贮藏期间均呈下降趋势,但茌梨果实的硬度在贮藏后期明显高于黄金梨果实;黄金梨果实中的可溶性果胶含量明显高于茌梨果实;7个PcEXPA基因在2个品种梨果实中的表达模式显示,PcEXPA2基因在茌梨果实和黄金梨果实中的表达与果实硬度变化和乙烯释放速率一致,且均受1-MCP下调,表明其可能参与了茌梨和黄金梨的成熟衰老进程。

番木瓜果实膨胀素基因部分序列的克隆及分析

膨胀素(Expansin)是一类存在于植物细胞壁上,并能快速缓冲张力,使植物细胞壁松驰的蛋白质。以成熟番木瓜果实总RNA反转录得到的cDNA为模板,设计简并引物进行PCR,得到1个大小为531bp的基因片段,编码177个氨基酸,并存在expansin的保守区域,命名为Cp-EXP1。番木瓜expansin的成功克隆为研究番木瓜的生长发育以及其品种的改良等打下了良好的基础。

香蕉果实expansin cDNA克隆及序列分析

提取成熟香蕉果肉的RNA并分离mRNA,以mRNA反转录合成cDNA,以该cDNA为模板,设计expansin的简并引物,进行RT PCR(退火温度为50℃).得到的扩增产物纯化后与pGEM T Easy载体连接,转化大肠杆菌,任意挑选2个阳性克隆,进行序列分析,结果得到2个序列相同的expansin的cDNA基因片段,命名为MA Exp3(以示与已登录的香蕉MA Exp1和MA Exp2的区别).MA Exp3中存在expansin基因的保守区域,即8个半胱氨酸残基和3个色氨酸残基,它编码177个氨基酸,与MA Exp1的核苷酸同源性为74 2%,氨基酸同源性为86 4%.

植物抗逆性与细胞壁expansin的关系概述

Expansin是在高等植物细胞壁中发现的一类富含羟脯氨酸的与细胞壁伸展性有关的糖蛋白,它在植物发育过程以及植物抗逆性方面均有作用。为此,综述了植物在经历低温、不同土壤水分、病害和盐害等逆境条件以及正常生长条件下expansin在细胞壁的积累变化情况,并对expansin的应用前景给予一定的阐述。

Cloning and Sequence Analysis of Expansin Genes from Litchi chinensis Fruit

Using PCR degenerate primers, designed with reference to the sequences of the conserved amino acids of known expansins, to amplify cDNA fragments in litchi fruit by RT-PCR, two different cDNA fragments , named as Lc-Exp1 and Lc-Exp2 , were cloned. Lc-Exp1 and Lc-Exp2 was respectively composed of 531 bp encoding 177 amino acids and 537 bp encoding 179 amino acids. Eight cysteine residues and three tryp-tophan residues, which is supposed to be the characteristics of expansins, are conserved in both Lc-Exp1 and c-Exp2. In addition, the homology between the two expansins is 71. 6% at nucleotide acid sequences and 76.3% at amino acid sequences. The homology of Lc-Exp1 with Fa-Exp2 or Pp-Exp1 was 92.7% or 92.1%, but that of Lc-Exp2 with Fa-Exp2 or Pp-Exp1 was only 77. 4% or 76.3% at amino acid sequences.

Exp2 polymorphisms associated with variation for fiber quality properties in cotton(Gossypium spp.)

Plant expansins are a group of extracellular proteins thought to affect the quality of cotton fibers. Previous expression profile analysis revealed that six Expansin A genes are present in cotton, of which two(GhExp1 and GhExp2) produce transcripts that are specific to the developing cotton fiber. To identify the phenotypic function of Exp2, and to determine whether nucleotide variation among alleles of Exp2 affects fiber quality, candidate gene association mapping was conducted. Gene-specific primers were designed to amplify the Exp2 gene. By amplicon sequencing, the nucleotide diversity of Exp2 was investigated across92 accessions(including 7 Gossypium arboreum, 74 Gossypium hirsutum, and 11 Gossypium barbadense accessions) with different fiber qualities. Twenty-six SNPs and seven InDels including 14 from the coding region of Exp2 were detected, forming twelve distinct haplotypes in the cotton collection. Among the 14 SNPs in the coding region, five were missense mutations and nine were synonymous nucleotide changes. The average SNP/InDel per nucleotide ratio was 2.61%(one SNP per 39 bp), with 1.81 and 3.87% occurring in coding and non-coding regions, respectively. Nucleotide and haplotype diversity across the entire Exp2 region was 0.00603(π) and 0.844, respectively, and diversity in non-coding regions was higher than that in coding regions. For linkage disequilibrium(LD), the mean r2 value for all polymorphism loci pairs was 0.48, and LD did not decay over 748 bp. Based on132 simple sequence repeat(SSR) loci evenly covering 26 chromosomes, the population structure was estimated, and the accessions were divided into seven groups that agreed well with their genomic origin and evolutionary history. A general linear model was used to calculate the Exp2-wide diversity–trait associations of 5 fiber quality traits, considering population structure(Q). Four SNPs in Exp2 were associated with at least one of the fiber quality traits, but not with fiber elongation. The highest positive effect on UHML and STR was observed for haplotype Hap_6 of Exp2. There was a significant association of Exp2 with fiber quality traits. There were many haplotypes in the Exp2 region, of which the most favorable was Hap_6. The association between nucleotide diversity and these fiber traitssheds light on the gene's potential contribution to the improvement of fiber quality, and should be useful to facilitate MAS programs in cotton.

Cloning and expression analysis of a homologous expansin gene EXP2 in Picea wilsonii

Expansins are cell-wall-loosening proteins that have multiple roles during plant development and stress- related processes. In this study, a novel expansin gene PwEXP2 was cloned by rapid amplification of cDNA ends based on the cDNA library of Picea wilsonii and EST fragment of PwEXP2. It was found that PwEXP2 coded 253 amino acids, and putative signal peptides exist at the N-terminal, followed by 8 cysteines, a HFD （His-Phe-Asp） conserved domain, and 4 tryptophan residues at the C-terminal. PwEXP2 was located in cytoplasm and nucleus when transformed in an onion epidermal cell. Quantitative real-time PCR assays showed that PwEXP2 was expressed in various tissues with a relatively high level in needles and low level in mature pollen. The expression level of PwEXP2 dramatically increased after seed germination. Gene expression profiles in abiotic stresses showed that PwEXP2 was induced by high temperature and osmotic stress but not involved in ABA-dependent signaling path- way. These results display the important roles of the PwEXP2 in plant development and multiple adversity stresses.

Overexpression of the apple expansin-like gene MdEXLB1 accelerates the softening of fruit texture in tomato

Fruit firmness is an important quality trait of apple fruit texture,and the pre-harvest ripening period is the key period for the formation of apple fruit texture.Expansin is a cell wall loosing protein family that has four subfamilies:α-expansin(EXPA),β-expansin(EXPB),expansin-like A(EXLA),and expansin-like B(EXLB).In this study,we investigated the key period of pre-harvest texture formation in‘Golden Delicious’apples based on fruit longitudinal diameter,transverse diameter,firmness,tissue structure,respiration intensity,ethylene release rate,and expansin activity.Within the 10 days before harvest,the fruit was found to reach maturity.Semi-quantitative RT-PCR revealed that most of the expansins were expressed at the ripening stage before harvest.The biological function of the EXLB subfamily gene,MdEXLB1,was further identified,and its subcellular localization on the cell wall was confirmed by transient transformation experiments.Compared with the wild type(WT),the transgenic tomato lines overexpressing MdEXLB1 had lower plant height,earlier fruiting period,fewer days for fruit ripening,higher fruit maturity,lower fruit firmness,higher fruit expansin activity,more discrete flesh cell structure,and accelerated fruit ripening process.Overall,this is the first study to propose that the apple EXLB subfamily gene,MdEXLB1,has biological functions and plays an important role in promoting fruit ripening and softening.

Expansin Genes Expressed Differentially in Peduncle Elongation of Near-Isogenic Wheat Rht Lines

The introduction of reduced height （Rht） genes Rht-Blb and Rht-Dlb led to impressive increases in wheat （Triticum aestivum L.） yields during the Green Revolution. In the present study, the dynamic elongation of peduncle in a set ofnear-isogenic lines （NILs） carrying different Rht alleles （Rht-Blb, Rht-Dlb, Rht-Blc, Rht-Dlb＋Rht-Blb, and Rht-Dlb＋Rht-Blc） were investigated. The reduction of the final length of peduncle in NILs was dependent mainly on the elongation rate, which was reduced by Rht genes, during rapid elongation phase. Resin sections showed that Rht genes strongly reduced the cell extension in peduncle. The expression of expansin genes, which mediate cell wall loosening and leading to cell expansion, were analysed by using real- time quantitative PCR （qPCR）. Among the 23 possible wheat expansin genes, 17 were expressed in the peduncle. The spatial distribution of expression was further analysed for five expansins that showed high expression levels in the peduncles of Rht lines. Compared to wild type plants, the incorporation of Rht-Dlb allele decreased about 37 and 80% of the expression levels of ExpA 7 and ExpA3 in elongation zone, respectively. The presence Rht-Blc dwarfing genes, however, produced 53% reduction in the expression level of ExpA7, and seriously decreased about 70% of ExpB9 expression. Although the expression levels of five genes exhibited variability among the lines, an expansin gene, ExpB2, showed its expression level highly associated with the cell elongation rate in peduncle of different Rht lines.