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The Arabidopsis floral organ identity genes APETALA3 (AP3) and PISTILLATA (PI) encode related DNA-binding proteins of the MADS family. Considerable evidence supports the hypothesis that a heterodimer of AP3 and PI is an essential component of B class activity. All ap3 and pi alleles characterized to date exhibit equivalent phenotypic defects in both whorls 2 and 3. In strong ap3 and pi mutants, petals and stamens are missing and sepals and carpels develop in their place. Weak ap3 and pi mutants exhibit partial conversions of petals to sepals and stamens to carpels. In this report, we describe the isolation and characterization of pi-5, an unusual B class mutant that exhibits defects in whorl 2 where sepals develop in place of petals, but third whorl stamens are most often normal. pi-5 flowers resemble those from 35S::SEP3 antisense plants. pi-5 contains missense mutation in the K domain (PIE125K). PIE125K exhibits defects in heterodimerization with its partner protein AP3. Via a reverse yeast two-hybrid screen, AP3K139E was isolated as a compensatory mutant of PIE125K. The compensatory interaction between PIE125K and AP3K139E is observed both in yeast two-hybrid assays and in planta. On its own, AP3K139E exhibits defects in specifying both petal and stamen identity. In addition, PIE125K is defective in interaction with SEPALLATA proteins in both two- and three-hybrid assays suggesting that PIE125K is defective in forming higher order complexes of MADS proteins. The decreased concentration of PI/AP3/SEP complexes offers an explanation for the petal defects observed in both pi-5 and 35S::SEP3 antisense plants. 相似文献
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Di Stilio VS Kramer EM Baum DA 《The Plant journal : for cell and molecular biology》2005,41(5):755-766
In most dioecious angiosperm species, flowers are initially perfect but abort either stamens or carpels during their development, indicating that sex determination occurs after floral organ identity has been established. Dioecious members of the genus Thalictrum (meadow-rue), however, produce flowers that lack aborted organs. Examination of early flower development of T. dioicum confirms that flowers are male or female from inception, raising the possibility that genetic mechanisms working at or above the level of organ identity promote sex determination through a homeotic-like mechanism. In order to investigate this possibility, we identified homologs of the organ identity genes PISTILLATA (PI), APETALA3 (AP3) and AGAMOUS (AG) from T. dioicum and the hermaphroditic species T. thalictroides. A combination of early and late duplication events was uncovered in these gene lineages and expression analyses indicate that these events are generally associated with divergence in gene regulation. In light of these findings, we discuss the potential of T. dioicum as a new model for the study of sex determination in the basal eudicots. 相似文献
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The MADS proteins APETALA3 (AP3), PISTILLATA (PI), SEPALLATAI (SEPI), SEP2, SEP3, AGAMOUS, and APETALA are required for proper floral organ identity in Arabidopsis flowers. All of these floral MADS proteins conserve two domains: the MADS domain that mediates DNA binding and dimerization, and the K domain that mediates protein protein interaction. The K domain is postulated to form a several amphipathic c-helices referred to as K1, K2, and K3. The K1 and K2 helicies are located entirely within the K domain while the K3 helix spans the K domain-C domain boundary. Here we report on our studies on the interactions of the B class MADS proteins AP3 and PI with the E class MADS proteins SEP1, SEP2, and SEP3. A comparative analysis of mutants in the K domain reveals that the subdomains mediating the PI/AP3 interaction are different from the subdomains mediating the PI/SEP3 (or PI/SEP1) interaction. The strong PI/SEP3 (or PI/SEP1) interaction requires K2, part of K3, and the interhelical region between K1 and K2. By contrast, K1, K2 and the region between K1 and K2 are important for strong AP3/PI interaction. Most of the K3 helix does not appear to be important for either the PI/AP3 or the PI/SEP3 (or PI/SEP1) interaction. Conserved hydrophobic positions are most important for the strength of both PI/AP3 and PI/SEP3 dimerization, though ionic and/or polar interactions appear to play a secondary role. 相似文献
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Wan-Ting Mao Wei-Han Hsu Jen-Ying Li Chang-Hsien Yang 《The Plant journal : for cell and molecular biology》2021,105(5):1357-1373
The floral quartet model proposes that plant MADS box proteins function as higher order tetrameric complexes. However, in planta evidence for MADS box tetramers remains scarce. Here, we applied a strategy using in vivo fluorescence resonance energy transfer (FRET) based on the distance change and distance symmetry of stable tetrameric complexes in tobacco (Nicotiana benthamiana) leaf cells to improve the accuracy of the estimation of heterotetrameric complex formation. This measuring system precisely verified the stable state of Arabidopsis petal (AP3/PI/SEP3/AP1) and stamen (AP3/PI/SEP3/AG) complexes and showed that the lily (Lilium longiflorum) PI co-orthologs LMADS8 and LMADS9 likely formed heterotetrameric petal complexes with Arabidopsis AP3/SEP3/AP1, which rescued petal defects of pi mutants. However, L8/L9 did not form heterotetrameric stamen complexes with Arabidopsis AP3/SEP3/AG to rescue the stamen defects of the pi mutants. Importantly, this system was applied successfully to find complicated tepal and stamen heterotetrameric complexes in lily. We found that heterodimers of B function AP3/PI orthologs (L1/L8) likely coexist with the homodimers of PI orthologs (L8/L8, L9/L9) to form five (two most stable and three stable) tepal- and four (one most stable and three stable) stamen-related heterotetrameric complexes with A/E and C/E function proteins in lily. Among these combinations, L1 preferentially interacted with L8 to form the most stable heterotetrameric complexes, and the importance of the L8/L8 and L9/L9 homodimers in tepal/stamen formation in lily likely decreased to a minor part during evolution. The system provides substantial improvements for successfully estimating the existence of unknown tetrameric complexes in plants. 相似文献
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Xuemei Chen José Luis Riechmann Dongxuan Jia Elliot Meyerowitz 《Sexual plant reproduction》2000,13(2):85-94
PISTILLATA (PI) is a floral homeotic B function gene in Arabidopsis and together with the other B function gene, APETALA3 (AP3), is involved in specifying petal and stamen identities. The expression of PI and AP3 is under similar developmental control. The initiation of AP3 and PI expression is at least partly caused by the floral meristem identity gene LEAFY, but the maintenance of AP3 and PI expression involves an autoregulatory loop requiring the activity of both genes. PI and AP3 are MADS domain proteins that form, and appear to function as, a heterodimer. AP3/PI binds in vitro to a sequence motif, CC(A/T)6GG, a MADS domain protein consensus binding site also known as the CArG box. We identified a 481-bp PI promoter region that confers both the initiation and the maintenance of PI expression patterns. We further dissected the promoter and identified minimal regions responsible for the AP3/PI-dependent expression. No CArG box is present in these minimal regions, suggesting that either AP3/PI does not bind directly to the PI promoter for the maintenance control, or that it requires additional factors to bind to the PI promoter. Our results suggest that the mechanisms of regulation of the two B function genes, AP3 and PI, are different, because CArG boxes are present in the AP3 promoter and are necessary for the AP3 feedback control. Received: 1 March 2000 / Revision accepted: 15 June 2000 相似文献
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Two rice MADS domain proteins interact with OsMADS1 总被引：1，自引：0，他引：1
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Wei P Liu X Hu MH Zuo LM Kai M Wang R Luo SZ 《Protein science : a publication of the Protein Society》2011,20(11):1814-1823
Experiments with the transmembrane (TM) domains of the glycoprotein (GP) Ib-IX complex have indicated that the associations between the TM domains of these subunits play an important role in the proper assembly of the complex. As a first step toward understanding these associations, we previously found that the Ibβ TM domain dimerized strongly in Escherichia coli cell membranes and led to Ibβ TM-CYTO (cytoplasmic domain) dimerization in the SDS-PAGE assay, while neither Ibα nor IX TM-CYTO was able to dimerize. In this study, we used the TOXCAT assay to probe the Ibβ TM domain dimerization interface by Ala- and Leu-scanning mutagenesis. Our results show that this interface is based on a leucine zipper-like heptad repeat pattern of amino acids. Mutating either one of polar residues Gln129 or His139 to Leu or Ala disrupted Ibβ TM dimerization dramatically, indicating that polar residues might form part of the leucine zipper-based dimerization interface. Furthermore, these specific mutational effects in the TOXCAT assay were confirmed in the thiol-disulfide exchange and SDS-PAGE assays. The computational modeling studies further revealed that the most likely leucine zipper interface involves hydrogen bonding of Gln129 and electrostatic interaction of the His139 side chain. Correlation of computer modeling results with experimental mutagenesis studies on the Ibβ TM domain may provide insights for understanding the role of the association of TM domains on the assembly of GP Ib-IX complex. 相似文献
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利用异质DNA探针 ,从拟南芥叶片cDNA文库中筛选到一个阳性cDNA克隆———AT10 3。DNA序列分析表明 ,其编码产物含有一个亮氨酸拉链结构域和一个核定位信号肽。GenBank数据库搜寻结果显示 ,AT10 3未与任何已知功能基因有同源性 ,但与裂叶牵牛PNZIP、集胞藻的一个ORF、紫菜的一个ORF ,构成了一个在进化上非常保守的含有亮氨酸拉链结构域的新家族 ,极有可能是一新的核基因转录因子。AT10 3是一个单拷贝基因 ,在叶片组织中强烈表达并受光调节 相似文献
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Actin 结合蛋白 p57 与 actin 之间存在相当复杂的作用机制 . 为深入了解这一机制,利用体外 F-actin 结合共沉淀、细胞内免疫荧光共定位以及免疫印迹和吸光度扫描分析等实验技术,系统地研究了亮氨酸拉链结构域在 p57 与 actin 结合中的作用 . 结果显示,亮氨酸拉链序列区域本身没有 actin 结合活性,但该区域缺失突变以及破坏亮氨酸拉链结构域的点突变都可以显著降低 p57 同 actin 的结合能力 . 同时,体内和体外的半定量分析结果表明,这两种突变导致 p57 同 actin 的结合能力的降低程度十分相近 . 这些结果充分说明亮氨酸拉链结构域在 p57 与 actin 的结合中起到了重要作用 . 相似文献
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APETALA3(AP3)/DEFICIENS(DEF)和PISTILLATA(PI)/GLOBOSA(GLO)为植物花器官发育B类基因,控制双子叶植物花瓣和雄蕊的发育,它们属于MADS-box基因家族,编码转录因子,这些基因的突变能导致花瓣转变为萼片,雄蕊转变为心皮。近年来已经在多种植物中克隆到了AP3/DEF和PI/GLO基因,AP3/DEF和PI/GLO基因在拟南芥中只在花器官中表达,而在玉米等植物维管束、叶片等组织中也有表达。现对有关AP3/DEF和PI/GLO基因表达及其在植物系统发育学研究方面的进展进行综述。 相似文献
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P‐selectin glycoprotein ligand‐1 (PSGL‐1) is a homodimeric mucin ligand that is important to mediate the earliest adhesive event during an inflammatory response by rapidly forming and dissociating the selectin‐ligand adhesive bonds. Recent research indicates that the noncovalent associations between the PSGL‐1 transmembrane domains (TMDs) can substitute for the C320‐dependent covalent bond to mediate the dimerization of PSGL‐1. In this article, we combined TOXCAT assays and molecular dynamics (MD) simulations to probe the mechanism of PSGL‐1 dimerization. The results of TOXCAT assays and Martini coarse‐grained molecular dynamics (CG MD) simulations demonstrated that PSGL‐1 TMDs strongly dimerized in a natural membrane and a leucine zipper motif was responsible for the noncovalent dimerization of PSGL‐1 TMD since mutations of the residues that occupied a or d positions in an (abcdefg)n leucine heptad repeat motif significantly reduced the dimer activity. Furthermore, we studied the effects of the disulfide bond on the PSGL‐1 dimer using MD simulations. The disulfide bond was critical to form the leucine zipper structure, by which the disulfide bond further improved the stability of the PSGL‐1 dimer. These findings provide insights to understand the transmembrane association of PSGL‐1 that is an important structural basis for PSGL‐1 preferentially binding to P‐selectin to achieve its biochemical and biophysical functions. 相似文献
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WANG Xin WANG Duncheng CHEN Xing HU Meiru WANG Jian’an LI Yan GUO Ning SHEN Beifen 《中国科学：生命科学英文版》2001,44(1):99-105
Our previous studies showed that some nuclear proteins that were expressed especially during terminal differentiation of erythroid cells might interact directly or indirectly with HS2 sequence to form the HS2-protein complexes and thus play an important role in the globin gene regulation and erythroid differentiation. Monoclonal antibodies against the nuclear proteins of terminal differentiated erythroid cells, including intermediate and late erythroblasts of human fetal liver and hemin induced K562 cells, were prepared by hybridoma technique. The monoclonal antibodies were used to screen λ-gtll human cDNA expression library of fetal liver in order to obtain the relevant cDNA clones. By the analysis of their cDNA clones and the identification of the proteins' functions, the regulation mechanism of the HS2 binding proteins might be better understood. Two cDNA clones (GenBank accession number AF040247 and AF040248 respectively) were obtained and one of them owns a full length and the other encodes a prote 相似文献
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Vladimir V. Egorov Natalia A. Grudinina Dmitry V. Lebedev Aram A. Shaldzhyan Alexander V. Slita Alexey K. Sirotkin Andrey V. Vasin Michael M. Shavlovsky 《朊病毒》2013,7(3):248-253
Myocilin is a protein with a molecular weight near 50 kDa. It is expressed in almost all organs and tissues.1 We showed that the peptide DQL ETQ TRE LET AYS NLL RD corresponding to N-terminal Leucine zipper motif (LZM) of the protein is able to form amyloid-like fibrils. The possible role of this motif in myocilin aggregation is discussed. 相似文献
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Duplicated APETALA1/FRUITFULL (AP1/FUL) genes show distinct but overlapping patterns of expression within rice (Oryza sativa) and within ryegrass (Lolium temulentum), suggesting discrete functional roles in the transition to flowering, specification of spikelet meristem identity, and specification of floral organ identity. In this study, we analyzed the expression of the AP1/FUL paralogues FUL1 and FUL2 across phylogenetically disparate grasses to test hypotheses of gene function. In combination with other studies, our data support similar roles for both genes in spikelet meristem identity, a general role for FUL1 in floral organ identity, and a more specific role for FUL2 in outer floral whorl identity. In contrast to Arabidopsis AP1/FUL genes, expression of FUL1 and FUL2 is consistent with an early role in the transition to flowering. In general, FUL1 has a wider expression pattern in all spikelet organs than FUL2, but both genes are expressed in all spikelet organs in some cereals. FUL1 and FUL2 appear to have multiple redundant functions in early inflorescence development. We hypothesize that sub-functionalization of FUL2 and interaction of FUL2 with LHS1 could specify lemma and palea identity in the grass floret. 相似文献
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