F-box蛋白家族的功能研究进展

F-box蛋白是一类含有F-box基序(motif),在泛素介导的蛋白质水解过程中具有底物识别特性的蛋白质家族.这类蛋白质在细胞时相转换、信号传导、发育等多种生理过程中都具有重要功能.     

F-box蛋白在植物生长发育中的功能研究进展

在真核生物中,由泛素介导的蛋白降解途径与植物生长发育密切相关。F-box蛋白家族是一类含有Fbox基序(motif),在泛素介导的蛋白质水解过程中具有底物识别特性的蛋白质家族。目前,从各种植物中已鉴定出大量的F-box蛋白质,这类蛋白质在植物激素的信号转导、光信号转导、自交不亲和以及花器官发育等许多生理过程中都具有重要功能。研究发现F-box蛋白在调控植物生长发育过程中所发挥的功能与其结构及泛素蛋白酶体途径密切相关。     

拟南芥F-box基因At3g16740的表达分析

拟南芥At3g16740基因为F-box基因家族成员,其功能尚不清楚.通过连续和瞬时光照处理分析,发现蓝光、红光和远红光都诱导At3g16740基因的表达,其中远红光的诱导作用最明显.蓝光受体cry1、cry2,红光受体phyB或远红光受体phyA突变导致At3g16740基因表达的光诱导作用减弱或者消失,表明该基因为光信号通路相关基因.通过实时荧光定量PCR分析At3g16740基因在拟南芥不同组织器官中的表达,发现其在拟南芥根、茎、叶、花和果荚中都有表达,花和果荚中的表达量最高,推测该基因可能参与植物花和/或果荚的发育.酵母双杂交分析发现,At3g16740蛋白通过F-box结构域与拟南芥ASK(arabidopsis-SKP1-like)家族成员ASK1、ASK2和ASK11相互作用,表明At3g16740是SCF(Skp、Cullin、F-box)复合物的成员.     

F-box蛋白家族及其功能

F-box蛋白是一类广泛存在于真核生物中,含有F-box结构域的蛋白家族,在泛素-蛋白酶体途径（ubiquitin-proteasome pathway, UPP）中因特异识别底物蛋白而参与细胞周期调控、转录调控、细胞凋亡、细胞信号转导等生命活动。另外,F-box蛋白还通过其他作用方式参与了体内众多生化过程。本文综述了F-box蛋白的结构和作用途径,以及该蛋白参与的多种生理功能,展示了F-box蛋白家族在生命活动中具有广泛而重要的作用,并指出了F-box蛋白将为阐明疾病发生机制提供新的线索,可望成为疾病治疗中药物作用的靶向位点。     

植物调控枢纽miR156及其靶基因SPL家族研究进展

SPL(SQUAMOSA promoter binding like)家族蛋白是植物特有的一类具有多功能的转录因子家族。在拟南芥中,SPL家族的11个基因受miR156的调控。该家族成员蛋白质都含有十分保守的SBP结构域,该结构域包含2个Zn2+结合位点和1个核定位信号序列。近年来,已从多种植物中分离出miR156及SPL基因。越来越多的研究表明,miR156及SPL家族参与了植物的生长发育、代谢调节及非生物胁迫等多种生物过程,成为植物生长发育的调控枢纽。本文综述了miR156及SPL家族在阶段转变、叶片发育、次生代谢及非生物胁迫等过程中的分子机制,并对其研究前景提出展望。     

F-box蛋白质在植物生长发育中的功能

在真核生物中, 泛素介导的蛋白降解途径参与了许多生物学过程。SCF复合体是一种非常重要的E3泛素连接酶, 在植物中研究的最为深入。F-box蛋白包含一个F-box 基序, 是SCF复合体的一个亚基, 它决定了底物识别的特异性。目前, 从各种植物中已鉴定出大量的F-box蛋白质, 它们参与了植物激素(乙烯, 生长素, GA, JA)的信号传导以及自交不亲和、花器官发育等生物学过程, F-box蛋白还参与了植物的胁迫反应。最新研究结果显示, 一个F-box蛋白TIR1是生长素的受体。因此, F-box蛋白质介导的泛素化蛋白质降解途径可能是植物基因表达调控的重要机制。     

DEAD-box基因家族在拟南芥生长发育中的作用

在RNA代谢过程中,需要许多蛋白和核酸的参与,其中一类蛋白就是RNA解旋酶。RNA解旋酶通过水解ATP获得能量来参与RNA代谢的多个方面,包括核内转录、pre-mRNA的剪切、核糖体发生、核质运输、蛋白质翻译、RNA降解、细胞器内基因的表达。DEAD-box蛋白家族是RNA解旋酶中最大的亚家族,它具有9个保守结构域,因motifyⅡ的保守氨基酸序列Asp-Glu-Ala-Asp(DEAD)而命名。该家族在酵母、拟南芥(Arabidopsis thaliana Heynh.)和人类基因组中都有较多的家庭成员。近年来,研究者对拟南芥DEAD-box蛋白家族的结构和功能进行了一些研究,本文着重总结DEAD-box基因家族对拟南芥生长发育的影响。     

天冬氨酸蛋白酶在拟南芥和水稻中的分子进化、表达模式以及在花药发育中的功能分析

天冬氨酸蛋白酶(aspartic proteases,APs)是一类功能多样化的酶,参与了植物大部分生理和发育过程,但其基因家族在植物中的系统分类、分子进化以及功能方面研究仍很欠缺。本研究收集整理了拟南芥和水稻中APs基因序列、分类、基因结构和染色体定位等信息,对比分析该基因家族在拟南芥和水稻中分子进化方面的差异;利用转录组数据阐明该家族基因在不同组织部位和不同发育时期的表达差异和功能分化。此外,本文还围绕花药发育的过程,细致分析了各亚家族APs基因的表达变化,推测APs在花药发育过程中的可能功能。     

F-box蛋白家族在肿瘤发生中的作用

SCF(Skp1-Cullin1-F-box)复合体是一类泛素E3连接酶,F-box蛋白是构成SCF复合体的亚基之一,在泛素蛋白酶体途径(ubiquitin-proteasome pathway,UPP)中介导SCF复合体特异性的识别底物。SCF复合体通过降解特定底物在多种细胞进程中发挥关键调节作用,如细胞增殖、细胞周期进程、转录和细胞凋亡等。F-box蛋白参与的蛋白降解过程的失调会导致肿瘤的发生,所以可针对F-box蛋白进行癌症药物的设计。该文主要对F-box蛋白家族的结构特征和它们在肿瘤发生中的功能进行了系统阐述,为其将来作为药物靶点应用于癌症临床治疗提供理论基础。     

拟南芥F-box基因At5g22700的功能初步分析

F-box蛋白作为SCF（Skpl,Cullin and anF-boxprotein）复合体的成员,参与调节植物的生长发育过程。At5g22700为功能未知的F-box基因家族成员。本研究通过酵母双杂交分析At5g22700蛋白与ASK（Arabidop-sis-SKP1-1ike）家族蛋白的相互作用,发现At5g22700蛋白的F-box结构域与ASK4蛋白相互作用。实时定量PCR分析该基因在不同组织器官中的表达,发现该基因在根和花中的表达量最高,说明At5g2700可能在根和花的发育中具有重要作用。以At5g22700基因的T—DNA插入突变体和过量表达转基因株系为材料,分析不同光照条件下幼苗的表型,发现蓝光下At5g22700过量表达转基因幼苗的主根比野生型长。这些研究结果表明,At5g22700在植物体内可能形成SCF复合体,并在植物幼苗主根伸长生长中起促进作用。     

The Egg apparatus 1 gene from maize is a member of a large gene family found in both monocots and dicots

The maize ZmEA1 protein was recently postulated to be involved in short-range pollen tube guidance from the embryo sac. To date, EA1-like sequences had only been identified in monocot species. Using a more conserved C-terminal motif found in the monocot species, numerous ZmEA1-like sequences were retrieved in EST databases from dicot species, as well as from unannotated genomic sequences of Arabidopsis thaliana. RT-PCR analyses were produced for these unannotated genes and showed that these were indeed expressed genes. Further structural and phylogenetic analyses revealed that all members of the EA1-like (EAL) gene family shared a conserved 27–29 amino acid motif, termed the EA box near the C-terminal end, and appear to be secretory proteins. Therefore, the EA box proteins defines a new class of small secretory proteins, some of which being possibly involved in pollen tube guidance. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Genetic transformation of Arabidopsis lyrata: specific expression of the green fluorescent protein (GFP) in pistil tissues

Arabidopsis thaliana has become widely used as a model system for plant biology. Recent phylogenetic studies led to a severe revision of the systematic relationships across species of the Brassicaceae family. This provided an opportunity to examine close relatives of A. thaliana and to study the function and molecular evolution of genes that play roles in ecology and speciation. In this context, developing tools to genetically transform “non-model plants” appears as a major issue to ascertain gene function. Here, we report a method to transform A. lyrata, one of the closest relatives of A. thaliana.     

Two new oleosin isoforms with altered expression patterns in seeds of the Arabidopsis mutant fus3

Oleosins are proteins associated with lipid bodies mainly synthesised during seed development. Using a subtractive hybridisation approach two new members of the oleosin gene family of Arabidopsis thaliana have been isolated. The quantitative and temporal expression patterns of both genes are found to be affected in the fus3 mutant defective in late embryogenesis. This pattern is interpreted as a molecular marker for a mutant specific developmental change from a seed maturation toa germination pathway.     

A highly repeated DNA sequence in Arabidopsis thaliana

Summary Three members of a family of highly repeated DNA sequences from Arabidopsis thaliana have been cloned and characterized. The repeat unit has an average length of 180 bp and is tandemly repeated in arrays longer than 50 kb. This family represents more than one percent of the Arabidopsis genome. Sequence comparisons with tandemly repeated DNA sequences from other Cruciferae species show several regions of homology and a similar length of the repeat unit. Homologies are also found to highly repeated sequences from other plant species. When the sequence CCGG occurs in the repeated DNA, the inner cytosine is generally methylated.     

Characterization of oil palm MADS box genes in relation to the mantled flower abnormality

In vitro propagation of oil palm (Elaeis guineensis Jacq.) frequently induces a somaclonal variant called ‘mantled’ abnormality, in which the stamens of both male and female flowers are transformed into carpels. This leads to a reduced yield or complete loss of the harvest of palm oil. The high frequency of the abnormality in independent lines and the high reversal rate suggest that it is due to an epigenetic change. The type of morphological changes suggest that it involves homeotic MADS box genes that regulate the identity of the flower whorls. We have isolated a number of MADS box genes from oil palm inflorescences by a MADS box-directed mRNA display approach. The isolated partial cDNAs included genes that were likely to function at the initial stages of flowering as well as genes that may function in determination of the inflorescence and the identity of the flower whorls. For four genes that were homologous to genes known to affect the reproductive parts of the flower, full length cDNAs were isolated. These were a B-type MADS box gene which may function in the determination of stamen formation, a C-type gene expected to be involved in stamen and carpel formation, and two putative SEP genes which act in concert with the A-, B- and C-type MADS box gene in determining flower whorl formation. The B-type gene EgMADS16 was functionally characterized as a PISTILLATA orthologue; it was able to complement an Arabidopsis thaliana pi mutant. Whether EgMADS16, or any of the other EgMADS genes, are functionally involved in the mantled condition remains to be established.     

The maize autonomous element Activator (Ac) shows a minimal germinal excision frequency of 0.2%–0.5% in transgenic Arabidopsis thaliana plants

Summary The autonomous mobile element Activator from Zea mays was introduced into Arabidopsis thaliana via Agrobacterium-mediated gene transfer. The use of a chimaeric construct, where the Ac element is located in the leader of the neomycin phosphotransferase (NPT II) gene, enabled the excision of Ac to be monitored by assaying for the reconstitution of NPT II gene activity. Using this approach, the transpositional activity of AC was initially studied in primary transformants. About 50% of the regenerating Ac transformants showed evidence for excision of the element. Reintegration of Ac was confirmed by Southern blot analysis. Transposition events are transmitted to the F1 generation with a minimal frequency of 0.3%. In a few exceptional cases they are detected in a high proportion of the F1 generation. Seedlings from the F2 and F3 generations were assayed for the rate of germinal excisions by scoring for kanamycin resistance. The minimal frequency of germinal excision events amounts to 0.2%–0.5% and hence allows the use of the Ac element for gene tagging purposes in A. thaliana.     

<Emphasis Type="Italic">AOM3</Emphasis> and<Emphasis Type="Italic"> AOM4</Emphasis>: two MADS box genes expressed in reproductive structures of<Emphasis Type="Italic"> Asparagus officinalis</Emphasis>

The MADS box genes participate in different steps of vegetative and reproductive plant development, including the most important phases of the reproductive process. Here we describe the isolation and characterisation of two Asparagus officinalis MADS box genes, AOM3 and AOM4. The deduced AOM3 protein shows the highest degree of similarity with ZAG3 and ZAG5 of maize, OsMADS6 of rice and AGL6 of Arabidopsis thaliana. The deduced AOM4 protein shows the highest degree of similarity with AOM1 of asparagus, the SEP proteins of Arabidopsis and the rice proteins OsMADS8, OsMADS45 and OsMADS7. The high level of identity between AOM1 and AOM4 made impossible the preparation of probes specific for one single gene, so the hybridisation signal previously described for AOM1 is probably due to the expression of both genes. The expression profile of AOM3 and AOM1/AOM4 during flower development is identical, and similar to that of the SEP genes. Asparagus genes, however, are expressed not only in flower organs, but also in the different meristem present on the apical region of the shoot during the flowering season: the apical meristem and the three lateral meristems emerging from the leaf axillary region that will give rise to flowers and lateral inflorescences during flowering season, and to phylloclades and branches during the subsequent vegetative phase. The expression of AOM3 and AOM1/AOM4 in these meristems appears to be correlated with the reproductive function of the apex as the hybridisation signal disappears when the apex switches to vegetative function.