大豆生长素响应因子GmARF16参与调节叶片衰老进程

生长素响应因子(auxin response factors,ARFs)通过调节下游靶基因广泛参与植物生长发育过程,但ARFs如何调控植物叶片衰老的分子机制还不清楚。该文首先利用实时荧光定量PCR(q PCR)技术,分析大豆生长素响应基因Gm ARF16在叶片自然衰老、人工黑暗诱导衰老、外源植物生长素IAA处理条件下的表达模式,结果表明,该基因与叶片衰老调控密切相关,并且属于生长素的原初响应基因。为了进一步验证Gm ARF16基因的功能,采用农杆菌转化方法分别获得基因敲减(Gm ARF16-RNAi)和抗降解表达(m Gm ARF16)的转基因大豆植株。与非转基因对照相比,Gm ARF16-RNAi转基因大豆植株的叶片叶绿素含量和最大光量子效率(Fv/Fm)显著提高,叶片衰老标记基因(Gm CYSP1)的表达受到抑制,而m Gm ARF16转基因大豆植株则呈现出与Gm ARF16-RNAi转基因大豆植株相反的叶片生理表型。结果表明大豆生长素响应因子Gm ARF16正调节叶片的衰老进程。该研究表明,Gm ARF16在植物生长发育进程中发挥着重要作用。     

ARF和Aux/IAA调控果实发育成熟机制研究进展

生长素是调控果实发育成熟的重要植物激素之一。在生长素介导的信号转导机制中,ARF和Aux/IAA扮演重要的角色。ARF与生长素响应基因启动子区域内的生长素响应元件结合,促进或抑制基因的表达。Aux/IAA通过结构域Ⅲ和Ⅳ与ARF特异性结合,从而调节生长素早期应答基因的转录功能。研究表明,ARF因子参与调控果实形态发育、硬度和糖分积累等,Aux/IAA因子在授粉、果实形态发育等方面作用明显。此外ARF和Aux/IAA之间相互或与自身发生的互作以调控下游基因表达是植物体响应生长素信号的主要机制。介绍了ARF和Aux/IAA的结构特征、在不同植物中的分布状况以及与果实发育成熟的关系,同时讨论了ARF和Aux/IAA互作的研究现状,旨为进一步阐明生长素调控果实发育成熟的机制提供参考。     

生长素响应因子与植物的生长发育

生长素响应因子(Auxin response factor, ARF)作为一类调控生长素响应基因表达的转录因子, 是生长素研究的重要内容。它可与生长素响应基因启动子区域内的生长素响应元件结合, 促进或抑制基因的表达。文章介绍了植物体内ARF家族的分子生物学近年来的研究进展, 同时也讨论了ARF转录因子的结构、ARF基因的表达调控、ARF在植物生长发育及信号转导中的作用以及ARF对靶基因的调控机制等内容。植物ARF成员都有一定的同源性, 大多含有4个结构域, 在多种组织和器官中都有表达, 其表达受到转录及转录后调控, 并且在介导生长素与其它激素之间相互作用方面扮演重要角色。     

早期生长素响应蛋白在生长素信号转导中的作用

3种早期生长素响应蛋白--生长素/吲哚乙酸蛋白(Aux/IAAs)、生长素响应因子(ARFs)和泛素介导的蛋白降解途径组分在生长素的信号转导中起着关键性的作用.目前的研究结果支持负调控模型的说法,即Aux/IAAs蛋白以生长素依赖的方式通过泛素相关的蛋白降解机制为26S蛋白酶降解.当Aux/IAAs-Aux/IAAs以及Aux/IAAs-ARFs二聚体含量降低时,ARFs-ARFs水平升高,ARFs-ARFs结合在生长素调控基因启动子的生长素响应元件(AuxREs)上调节一系列基因的表达,进而引导植物的正常生长和发育.     

泛素降解途径与生长素的调节

就近几年来泛素降解途径在生长素调节中的作用作了介绍,主要是3个蛋白家族突变体的一系列分子分析研究,即生长素应答因子(auxin responsefactors,ARFs)、生长素/吲哚乙酸(Aux/IAA)家族和泛素蛋白酶解组分.ARFs可以直接与DNA结合,介导生长素调节的基因表达;Aux/IAA通过与ARFs形成异源二聚体阻碍ARFs执行功能;泛素降解途径包括泛素激活酶El、泛素连接酶E2、泛素连接酶E3及26S蛋白酶体.生长素通过促进Aux/IAA与E3-SCFTIR1的相互作用降解Aux/IAA蛋白,释放出的ARFs与DNA结合,调节生长素相关基因表达.COP9(constitutive photomorphogenic locus 9)信号体也通过调节SCFTIl活性参与此过程.     

生长素信号转导途径及参与的生物学功能研究进展

生长素参与植物生长和发育诸多过程,调控众多生理反应,在植物整个生命周期中自始至终发挥着调节作用.研究生长素的作用机制,对深入认识植物生长发育的生理过程有着重要的意义.综述了与生长素信号转导途径相关的3类主要蛋白组分:生长素/吲哚乙酸蛋白(auxin/indoleacetic acids proteins,Aux/IAAs)、生长素响应因子(auxin response factors,ARFs)和SCF(SKP1-CDC53/CUL1-F-box)复合体,及相关的SGT1(suppressor of the G2 allele of skp1)基因,并对生长素相关基因表达的模式及其生物学功能进行了总结.     

谷子ARF基因家族的鉴定与生物信息学分析

生长素应答因子(ARF,auxin response factors)是一类可以结合在生长素应答基因启动子部位的转录因子,在植物的生长发育中起至关重要的作用。本研究以谷子为材料,共鉴定出24个ARF基因,命名为Si ARFs。利用生物信息学对谷子Si ARFs基因的结构、染色体分布、基因倍增模式、系统进化以及基因的表达模式进行分析。结果表明,Si ARF基因家族在染色体上呈不均匀分布,除2号染色体外,其他染色体上都有该家族基因,基因的扩增模式为分散复制与片段复制。Si ARFs基因家族具有相对保守的结构,即包含1个保守的B3 DNA结构域、ARF结构域和Aux/IAA结构域,ARF蛋白的3D结构含有3个α螺旋和7个β折叠结构。进化树分析表明谷子ARF蛋白和物种相近的高粱、玉米聚在一起。大多数ARF基因在谷子根、茎、叶和穗中都有表达,且不同基因表达量有较大差异。     

植物生长素反应因子研究进展

生长素反应因子（ARFs）是植物生长和发育的重要调节因子,在生长素早期反应蛋白（Aux／IAAs）的参与下,通过和生长素反应基因启动子区AuxRE元件的JTGTCTC序列结合,共同调控这些基因的表达。近年来关于生长素反应因子的分子结构和ARF与Aux／IAA的相互作用及其对植物生长和发育的影响、作用的靶基因以及分子机制受到人们的重视,并在这些方面做了大量的研究。     

植物Aux/IAA基因家族生物学功能研究进展

生长素是最重要的植物激素之一, 对植物生长发育起着关键调控作用。生长素作用于植物后, 早期生长素响应基因家族Aux/IAA、GH3和SAUR等被迅速诱导, 基因表达上调。其中Aux/IAA基因家族编码的蛋白一般由4个保守结构域组成, 结构域I具有抑制生长素信号下游基因表达的作用, 结构域II在生长素信号转导中主要被TIR1调控进而影响Aux/IAA的稳定性, 结构域III/IV通过与生长素响应因子ARF相互作用调控生长素信号。Aux/IAA基因家族在双子叶植物拟南芥(Arabidopsis thaliana)的器官发育、根形成、茎伸长和叶扩张等方面发挥重要作用; 在单子叶植物水稻(Oryza sativa)和小麦(Triticum aestivum)中, 主要影响根系发育和株型, 但大多数Aux/IAA基因的功能尚不清楚。该文主要从Aux/IAA蛋白的结构、功能和生长素信号转导途径方面综述Aux/IAA家族在拟南芥、禾谷类作物及其它植物中的研究进展, 以期为全面揭示Aux/IAA家族基因的生物学功能提供线索。     

植物核糖基化因子ARF1的功能研究进展

二磷酸腺苷-核糖基化因子1(ADP-ribosylation factor1,ARF1)是二磷酸腺苷-核糖基化因子(ADP-ribosylation factors,ARFs)家族的一员,ARFs是GTP结合蛋白Ras超家族的一个亚家族,ARF家族在结构上非常保守,广泛存在于酵母以及植物和动物中。研究发现ARF1在植物生长过程中有着重要的作用,如参与囊泡运输,活化磷脂酶D,一些细胞器的维持,抗病毒等方面有着重要作用,是细胞内重要的信号分子。本研究主要介绍ARF1在植物中的进展。     

Deletion of MP/ARF5 domains III and IV reveals a requirement for Aux/IAA regulation in Arabidopsis leaf vascular patterning

Combinatorial interactions of AUXIN RESPONSE FACTORs (ARFs) and auxin/indole acetic acid (Aux/IAA) proteins through their common domains III and IV regulate auxin responses, but insight into the functions of individual proteins is still limited. As a new tool to explore this regulatory network, we generated a gain-of-function ARF genotype by eliminating domains III and IV from the functionally well-characterized ARF MONOPTEROS(MP)/ARF5. This truncated version of MP, termed MPΔ, conferred complementing MP activity, but also displayed a number of semi-dominant traits affecting auxin signaling and organ patterning. In MPΔ, the expression levels of many auxin-inducible genes, as well as rooting properties and vascular tissue abundance, were enhanced. Lateral organs were narrow, pointed and filled with parallel veins. This effect was epistatic over the vascular hypotrophy imposed by certain Aux/IAA mutations. Further, in MPΔ leaves, failure to turn off the procambium-selecting gene PIN1 led to the early establishment of oversized central procambial domains and very limited subsequent lateral growth of the leaf lamina. We conclude that MPΔ can selectively uncouple a single ARF from regulation by Aux/IAA proteins and can be used as a genetic tool to probe auxin pathways and explore leaf development.     

A role for auxin response factor 19 in auxin and ethylene signaling in Arabidopsis

Although auxin response factors (ARFs) are the first well-characterized proteins that bind to the auxin response elements, elucidation of the roles of each ARF gene in auxin responses and plant development has been challenging. Here we show that ARF19 and ARF7 not only participate in auxin signaling, but also play a critical role in ethylene responses in Arabidopsis (Arabidopsis thaliana) roots, indicating that the ARFs serve as a cross talk point between the two hormones. Both arf19 and arf7 mutants isolated from our forward genetic screens are auxin resistant and the arf19arf7 double mutant had stronger auxin resistance than the single mutants and displayed phenotypes not seen in the single mutants. Furthermore, we show that a genomic fragment of ARF19 not only complements arf19, but also rescues arf7. We conclude that ARF19 complements ARF7 at the protein level and that the ARF7 target sequences are also recognized by ARF19. Therefore, it is the differences in expression level/pattern and not the differences in protein sequences between the two ARFs that determines the relative contribution of the two ARFs in auxin signaling and plant development. In addition to being auxin resistant, arf19 has also ethylene-insensitive roots and ARF19 expression is induced by ethylene treatment. This work provides a sensitive genetic screen for uncovering auxin-resistant mutants including the described arf mutants. This study also provides a likely mechanism for coordination and integration of hormonal signals to regulate plant growth and development.     

Tissue-specific expression of stabilized SOLITARY-ROOT/IAA14 alters lateral root development in Arabidopsis

Auxin is important for lateral root (LR) initiation and subsequent LR primordium development. However, the roles of tissue-specific auxin signaling in these processes are poorly understood. We analyzed transgenic Arabidopsis plants expressing the stabilized mutant INDOLE-3 ACETIC ACID 14 (IAA14)/SOLITARY-ROOT (mIAA14) protein as a repressor of the auxin response factors (ARFs), under the control of tissue-specific promoters. We showed that plants expressing the mIAA14-glucocorticoid receptor (GR) fusion protein under the control of the native IAA14 promoter had the solitary-root/iaa14 mutant phenotypes, including the lack of LR formation under dexamethasone (Dex) treatment, indicating that mIAA14-GR is functional in the presence of Dex. We then demonstrated that expression of mIAA14-GR under the control of the stele-specific SHORT-ROOT promoter suppressed LR formation, and showed that mIAA14-GR expression in the protoxylem-adjacent pericycle also blocked LR formation, indicating that the normal auxin response mediated by auxin/indole-3 acetic acid (Aux/IAA) signaling in the protoxylem pericycle is necessary for LR formation. In addition, we demonstrated that expression of mIAA14-GR under either the ARF7 or the ARF19 promoter also suppressed LR formation as in the arf7 arf19 double mutants, and that IAA14 interacted with ARF7 and ARF19 in yeasts. These results strongly suggest that mIAA14-GR directly inactivates ARF7/ARF19 functions, thereby blocking LR formation. Post-embryonic expression of mIAA14-GR under the SCARECROW promoter, which is expressed in the specific cell lineage during LR primordium formation, caused disorganized LR development. This indicates that normal auxin signaling in LR primordia, which involves the unknown ARFs and Aux/IAAs, is necessary for the establishment of LR primordium organization. Thus, our data show that tissue-specific expression of a stabilized Aux/IAA protein allows analysis of tissue-specific auxin responses in LR development by inactivating ARF functions.