Plant-specific Protein Family Research Articles

Arabidopsis senescence-associated protein DMP1 is involved in membrane remodeling of the ER and tonoplast

BackgroundArabidopsis DMP1 was discovered in a genome-wide screen for senescence-associated membrane proteins. DMP1 is a member of a novel plant-specific membrane protein family of unknown function. In rosette leaves DMP1 expression increases from very low background level several 100fold during senescence progression.ResultsExpression of AtDMP1 fused to eGFP in Nicotiana benthamiana triggers a complex process of succeeding membrane remodeling events affecting the structure of the endoplasmic reticulum (ER) and the vacuole. Induction of spherical structures (“bulbs”), changes in the architecture of the ER from tubular to cisternal elements, expansion of smooth ER, formation of crystalloid ER, and emergence of vacuolar membrane sheets and foamy membrane structures inside the vacuole are proceeding in this order. In some cells it can be observed that the process culminates in cell death after breakdown of the entire ER network and the vacuole. The integrity of the plasma membrane, nucleus and Golgi vesicles are retained until this stage. In Arabidopsis thaliana plants expressing AtDMP1-eGFP by the 35S promoter massive ER and vacuole vesiculation is observed during the latest steps of leaf senescence, whereas earlier in development ER and vacuole morphology are not perturbed. Expression by the native DMP1 promoter visualizes formation of aggregates termed “boluses” in the ER membranes and vesiculation of the entire ER network, which precedes disintegration of the central vacuole during the latest stage of senescence in siliques, rosette and cauline leaves and in darkened rosette leaves. In roots tips, DMP1 is strongly expressed in the cortex undergoing vacuole biogenesis.ConclusionsOur data suggest that DMP1 is directly or indirectly involved in membrane fission during breakdown of the ER and the tonoplast during leaf senescence and in membrane fusion during vacuole biogenesis in roots. We propose that these properties of DMP1, exacerbated by transient overexpression, may cause or contribute to the dramatic membrane remodeling events which lead to cell death in infiltrated tobacco leaves.

Cloning of aZoysia ZjLsLand its overexpression to induce axillary meristem initiation and tiller formation inArabidopsisand bentgrass

Zoysia grass and creeping bentgrass are important turf grasses used in parks, gardens and playing fields. Development of grasses with increased tiller formation will enhance their commercial cultivation. To investigate the regulatory mechanism of tiller formation, we cloned the Zoysia japonica Lateral suppressor-like (ZjLsL) gene. The Lateral suppressor (Ls) gene encodes a transcriptional regulator belonging to the plant-specific GRAS protein family of putative transcription factors, and regulates axillary meristem initiation. A full-length DNA of the ZjLsL gene was isolated by 5'/3' DNA walking. Phylogenetic analysis showed that ZjLsL is closely related to Ls genes. Southern blot analysis revealed that zoysia grass has two copies of the ZjLsL gene. ZjLsL expression was detected in all organs of zoysia grass but was most highly expressed in culms. Overexpression of ZjLsL in creeping bentgrass and Arabidopsis plants promoted axillary bud formation. These results suggest that ZjLsL plays an important role in axillary meristem initiation and tiller formation.

Structure and regulation of the Asr gene family in banana

Abscisic acid, stress, ripening proteins (ASR) are a family of plant-specific small hydrophilic proteins. Studies in various plant species have highlighted their role in increased resistance to abiotic stress, including drought, but their specific function remains unknown. As a first step toward their potential use in crop improvement, we investigated the structure and regulation of the Asr gene family in Musa species (bananas and plantains). We determined that the Musa Asr gene family contained at least four members, all of which exhibited the typical two exons, one intron structure of Asr genes and the “ABA/WDS” (abscisic acid/water deficit stress) domain characteristic of Asr genes. Phylogenetic analyses determined that the Musa Asr genes were closely related to each other, probably as the product of recent duplication events. For two of the four members, two versions corresponding to the two sub-genomes of Musa, acuminata and balbisiana were identified. Gene expression and protein analyses were performed and Asr expression could be detected in meristem cultures, root, pseudostem, leaf and cormus. In meristem cultures, mAsr1 and mAsr3 were induced by osmotic stress and wounding, while mAsr3 and mAsr4 were induced by exposure to ABA. mASR3 exhibited the most variation both in terms of amino acid sequence and expression pattern, making it the most promising candidate for further functional study and use in crop improvement.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-011-1421-0) contains supplementary material, which is available to authorized users.

APO1 Promotes the Splicing of Chloroplast Group II Introns and Harbors a Plant-Specific Zinc-Dependent RNA Binding Domain

Arabidopsis thaliana APO1 is required for the accumulation of the chloroplast photosystem I and NADH dehydrogenase complexes and had been proposed to facilitate the incorporation of [4Fe-4S] clusters into these complexes. The identification of maize (Zea mays) APO1 in coimmunoprecipitates with a protein involved in chloroplast RNA splicing prompted us to investigate a role for APO1 in splicing. We show here that APO1 promotes the splicing of several chloroplast group II introns: in Arabidopsis apo1 mutants, ycf3-intron 2 remains completely unspliced, petD intron splicing is strongly reduced, and the splicing of several other introns is compromised. These splicing defects can account for the loss of photosynthetic complexes in apo1 mutants. Recombinant APO1 from both maize and Arabidopsis binds RNA with high affinity in vitro, demonstrating that DUF794, the domain of unknown function that makes up almost the entirety of APO1, is an RNA binding domain. We provide evidence that DUF794 harbors two motifs that resemble zinc fingers, that these bind zinc, and that they are essential for APO1 function. DUF794 is found in a plant-specific protein family whose members are all predicted to localize to mitochondria or chloroplasts. Thus, DUF794 adds a new example to the repertoire of plant-specific RNA binding domains that emerged as a product of nuclear-organellar coevolution.

Crystallization and preliminary crystallographic analysis of Arabidopsis thaliana EDS1, a key component of plant immunity, in complex with its signalling partner SAG101.

In plants, the nucleocytoplasmic protein EDS1 (Enhanced disease susceptibility1) is an important regulator of innate immunity, coordinating host-cell defence and cell-death programs in response to pathogen attack. Arabidopsis thaliana EDS1 stabilizes and signals together with its partners PAD4 (Phytoalexin deficient4) and SAG101 (Senescence-associated gene101). Characterization of EDS1 molecular configurations in vitro and in vivo points to the formation of structurally and spatially distinct EDS1 homomeric dimers and EDS1 heteromeric complexes with either PAD4 or SAG101 as necessary components of the immune response. EDS1, PAD4 and SAG101 constitute a plant-specific protein family with a unique `EP' (EDS1-PAD4-specific) domain at their C-termini and an N-terminal domain resembling enzymes with an α/β-hydrolase fold. Here, the expression, purification and crystallization of a functional EDS1 complex formed by EDS1 and SAG101 from Arabidopsis thaliana are reported. The crystals belonged to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 101.8, b = 115.9, c = 122.8 Å, and diffracted to 3.5 Å resolution.

Tangled localization at the cortical division site of plant cells occurs by several mechanisms

TANGLED (TAN) is the founding member of a family of plant-specific proteins required for correct orientation of the division plane. Arabidopsis thaliana TAN is localized before prophase until the end of cytokinesis at the cortical division site (CDS), where it appears to help guide the cytokinetic apparatus towards the cortex. We show that TAN is actively recruited to the CDS by distinct mechanisms before and after preprophase band (PPB) disassembly. Colocalization with the PPB is mediated by one region of TAN, whereas another region mediates its recruitment to the CDS during cytokinesis. This second region binds directly to POK1, a kinesin that is required for TAN localization. Although this region of TAN is recruited to the CDS during cytokinesis without first colocalizing with the PPB, pharmacological evidence indicates that the PPB is nevertheless required for both early and late localization of TAN at the CDS. Finally, we show that phosphatase activity is required for maintenance of early but not late TAN localization at the CDS. We propose a new model in which TAN is actively recruited to the CDS by several mechanisms, indicating that the CDS is dynamically modified from prophase through to the completion of cytokinesis.

The RST and PARP-like domain containing SRO protein family: analysis of protein structure, function and conservation in land plants

BackgroundThe SROs (SIMILAR TO RCD-ONE) are a group of plant-specific proteins which have important functions in stress adaptation and development. They contain the catalytic core of the poly(ADP-ribose) polymerase (PARP) domain and a C-terminal RST (RCD-SRO-TAF4) domain. In addition to these domains, several, but not all, SROs contain an N-terminal WWE domain.ResultsSROs are present in all analyzed land plants and sequence analysis differentiates between two structurally distinct groups; cryptogams and monocots possess only group I SROs whereas eudicots also contain group II. Group I SROs possess an N-terminal WWE domain (PS50918) but the WWE domain is lacking in group II SROs. Group I domain structure is widely represented in organisms as distant as humans (for example, HsPARP11). We propose a unified nomenclature for the SRO family. The SROs are able to interact with transcription factors through the C-terminal RST domain but themselves are generally not regulated at the transcriptional level. The most conserved feature of the SROs is the catalytic core of the poly(ADP-ribose) polymerase (PS51059) domain. However, bioinformatic analysis of the SRO PARP domain fold-structure and biochemical assays of AtRCD1 suggested that SROs do not possess ADP-ribosyl transferase activity.ConclusionsThe SROs are a highly conserved family of plant specific proteins. Sequence analysis of the RST domain implicates a highly preserved protein structure in that region. This might have implications for functional conservation. We suggest that, despite the presence of the catalytic core of the PARP domain, the SROs do not possess ADP-ribosyl transferase activity. Nevertheless, the function of SROs is critical for plants and might be related to transcription factor regulation and complex formation.

A member of the Whirly family is a multifunctional RNA- and DNA-binding protein that is essential for chloroplast biogenesis.

‘Whirly’ proteins comprise a plant-specific protein family whose members have been described as DNA-binding proteins that influence nuclear transcription and telomere maintenance, and that associate with nucleoids in chloroplasts and mitochondria. We identified the maize WHY1 ortholog among proteins that coimmunoprecipitate with CRS1, which promotes the splicing of the chloroplast atpF group II intron. ZmWHY1 localizes to the chloroplast stroma and to the thylakoid membrane, to which it is tethered by DNA. Genome-wide coimmunoprecipitation assays showed that ZmWHY1 in chloroplast extract is associated with DNA from throughout the plastid genome and with a subset of plastid RNAs that includes atpF transcripts. Furthermore, ZmWHY1 binds both RNA and DNA in vitro. A severe ZmWhy1 mutant allele conditions albino seedlings lacking plastid ribosomes; these exhibit the altered plastid RNA profile characteristic of ribosome-less plastids. Hypomorphic ZmWhy1 mutants exhibit reduced atpF intron splicing and a reduced content of plastid ribosomes; aberrant 23S rRNA metabolism in these mutants suggests that a defect in the biogenesis of the large ribosomal subunit underlies the ribosome deficiency. However, these mutants contain near normal levels of chloroplast DNA and RNAs, suggesting that ZmWHY1 is not directly required for either DNA replication or for global plastid transcription.

A small plant-specific protein family of ABI five binding proteins (AFPs) regulates stress response in germinating Arabidopsis seeds and seedlings

The transcription factor ABA-Insensitive5 (ABI5) is a key regulator of ABA signaling and stress response in Arabidopsis seeds and seedlings. Potential ABI5-interacting proteins were identified by a yeast two-hybrid screen; the most prevalent interactors were a family of four highly conserved plant-specific proteins with no domains of known function, but homology to a previously characterized ABI Five Binding Protein (AFP). This study compares expression and function of the family members. The AFPs are induced by ABA and/or dehydrating stresses in young seedlings, but the developmental timing of their induction differs. Mutations in AFP1 or AFP2 result in increased sensitivity to ABA and salt, whereas afp4 mutants are mildly ABA-resistant. AFP2, like AFP1, acts epistatically to ABI5. Reduced germination or seedling growth of the mutants under stress correlates with a higher level of ABI5 protein when compared to wild-type seedlings, but it is not clear whether this is a cause or effect of the reduced growth. Although both ABI5 and the AFPs are ABA-induced, the ABI5:AFP ratio increases at high ABA concentrations, maintaining growth inhibition under severe stress. An AFP2:GFP fusion, which complements the afp2 mutation, is nuclear-localized in seedlings exposed to stress, but becomes delocalized before being degraded following removal of stress. The AFPs may also interact to varying extents with many ABI5-related bZIP transcription factors. This study suggests that germination and seedling growth are regulated by antagonistic interactions among at least two functionally redundant families, the AFPs and the ABI5-related proteins, providing a mechanism to fine-tune seedling stress responses.

Overexpression of mtDNA-associated AtWhy2 compromises mitochondrial function

BackgroundStWhy1, a member of the plant-specific Whirly single-stranded DNA-binding protein family, was first characterized as a transcription factor involved in the activation of the nuclear PR-10a gene following defense-related stress in potato. In Arabidopsis thaliana, Whirlies have recently been shown to be primarily localized in organelles. Two representatives of the family, AtWhy1 and AtWhy3 are imported into plastids while AtWhy2 localizes to mitochondria. Their function in organelles is currently unknown.ResultsTo understand the role of mitochondrial Whirlies in higher plants, we produced A. thaliana lines with altered expression of the atwhy2 gene. Organellar DNA immunoprecipitation experiments demonstrated that AtWhy2 binds to mitochondrial DNA. Overexpression of atwhy2 in plants perturbs mitochondrial function by causing a diminution in transcript levels and mtDNA content which translates into a low activity level of respiratory chain complexes containing mtDNA-encoded subunits. This lowered activity of mitochondria yielded plants that were reduced in size and had distorted leaves that exhibited accelerated senescence. Overexpression of atwhy2 also led to early accumulation of senescence marker transcripts in mature leaves. Inactivation of the atwhy2 gene did not affect plant development and had no detectable effect on mitochondrial morphology, activity of respiratory chain complexes, transcription or the amount of mtDNA present. This lack of phenotype upon abrogation of atwhy2 expression suggests the presence of functional homologues of the Whirlies or the activation of compensating mechanisms in mitochondria.ConclusionAtWhy2 is associated with mtDNA and its overexpression results in the production of dysfunctional mitochondria. This report constitutes the first evidence of a function for the Whirlies in organelles. We propose that they could play a role in the regulation of the gene expression machinery of organelles.

P39, a Novel Soybean Protein Allergen, Belongs to a Plant-Specific Protein Family and Is Present in Protein Storage Vacuoles

Soybean lecithins are seeing increasing use in industry as an emulsifier and food additive. They are also a growing source of human food allergies, which arise principally from the proteins fractionating with the lecithin fraction during manufacture. A previous study (Gu, X.; Beardslee, T.; Zeece, M.; Sarath, G.; Markwwell, J. Int Arch. Allergy Immunol. 2001, 126, 218-225) identified several allergenic proteins in soybean lecithins and a soybean IgE-binding protein termed P39 was discovered. However, very little was known about this protein except that it was coded by the soybean genome. This paper investigates key biological and immunological properties of this potential soybean lecithin allergen. P39 is encoded by a multigene family in soybeans and in several other higher plants. The soybean P39-1 protein and its essentially indistinguishable homologue, P39-2, have been cloned and studied. These proteins and their homologues belong to a family of plant-specific proteins of unknown function. In soybeans, P39-1 is seed specific, and its transcript levels are highest in developing seeds and decline during seed maturation. In contrast, P39 protein was detectable only in the fully mature, dry seed. Subcellular fractionation revealed that P39 protein was strongly associated with oil bodies; however, immunolocalization indicated P39 was distributed in the matrix of the protein storage vacuoles, suggesting that association with oil bodies was an artifact arising from the extraction procedure. By the use of recombinant techniques it has also been documented that IgE-binding epitopes are present on several different portions of the P39-1 polypeptide.

Genome-Wide Annotation of Remorins, a Plant-Specific Protein Family: Evolutionary and Functional Perspectives

Remorins were discovered in a screen for plasma membrane (PM) proteins differentially phosphorylated in the presence of oligogalacturonides ([Farmer et al., 1989][1]). The first remorin was initially designated as pp34, as it corresponded to a phosphorylated protein with a molecular mass of 34 kD in

AtMAP70-5, a divergent member of the MAP70 family of microtubule-associated proteins, is required for anisotropic cell growth inArabidopsis

AtMAP70-5 is the most divergent of a recently described multigene family of plant-specific microtubule-associated proteins (MAPs). It is significantly smaller than other members and has several isoform-specific sequence features. To confirm that this protein still functions as a MAP we show that it directly binds microtubules in vitro and decorates microtubules in vivo. When added to tubulin polymerization assays, AtMAP70-5 increases the length distribution profile of microtubules indicating that it stabilizes microtubule dynamics. The overexpressed fusion protein perturbs cell polarity in cell suspensions by inducing extra poles for growth. Similarly, in Arabidopsis plants the overexpression of AtMAP70-5 causes epidermal cells to swell; it also stunts growth and induces right-handed organ twisting. RNAi-mediated downregulation of AtMAP70-5 results in reduced inflorescence stem length and diameter and individual cells are inhibited in their capacity for expansion. These observations suggest that the control over AtMAP70-5 expression levels is important in order to maintain axial polarity and to ensure regular extension of plant organs.

EDM2 is required for RPP7‐dependent disease resistance in Arabidopsis and affects RPP7 transcript levels

Specific disease resistance of Arabidopsis thaliana against the Hyaloperonospora parasitica isolate Hiks1 (HpHiks1) is mediated by RPP7. Although this disease resistance gene encodes a typical nucleotide binding site leucine-rich repeat (NB-LRR) disease resistance protein, its function is independent of the defense hormone salicylic acid and most known genes required for plant immune responses. We identified EDM2 (enhanced downy mildew 2) in a genetic screen for RPP7 suppressors. Mutations of EDM2 phenocopy RPP7 mutations, but do not affect other tested disease resistance genes. We isolated EDM2 by map-based cloning. The predicted EDM2 protein is structurally unrelated to previously identified components of the plant immune system, bears typical features of transcriptional regulators, including plant homeodomain (PHD)-finger-like domains, and defines a plant-specific protein family. In edm2 mutants both constitutive and HpHiks1-induced RPP7 transcript levels are reduced, suggesting that EDM2 is either a direct or an indirect regulator of RPP7 expression. Microarray analyses defined a set of defense-associated genes, the expression of which is suppressed during successful HpHiks1 colonization of either rpp7 or edm2 plants. This transcriptional phenotype is counteracted by an EDM2/RPP7-dependent mechanism.

The Plant-Specific ssDNA Binding Protein OSB1 Is Involved in the Stoichiometric Transmission of Mitochondrial DNA inArabidopsis

Plant mitochondrial genomes exist in a natural state of heteroplasmy, in which substoichiometric levels of alternative mitochondrial DNA (mtDNA) molecules coexist with the main genome. These subgenomes either replicate autonomously or are created by infrequent recombination events. We found that Arabidopsis thaliana OSB1 (for Organellar Single-stranded DNA Binding protein1) is required for correct stoichiometric mtDNA transmission. OSB1 is part of a family of plant-specific DNA binding proteins that are characterized by a novel motif that is required for single-stranded DNA binding. The OSB1 protein is targeted to mitochondria, and promoter-beta-glucuronidase fusion showed that the gene is expressed in budding lateral roots, mature pollen, and the embryo sac of unfertilized ovules. OSB1 T-DNA insertion mutants accumulate mtDNA homologous recombination products and develop phenotypes of leaf variegation and distortion. The mtDNA rearrangements occur in two steps: first, homozygous mutants accumulate subgenomic levels of homologous recombination products; second, in subsequent generations, one of the recombination products becomes predominant. After the second step, the process is no longer reversible by backcrossing. Thus, OSB1 participates in controlling the stoichiometry of alternative mtDNA forms generated by recombination. This regulation could take place in gametophytic tissues to ensure the transmission of a functional mitochondrial genome.

The GRAS protein SCL13 is a positive regulator of phytochrome-dependent red light signaling, but can also modulate phytochrome A responses

Phytochrome photoreceptors enable plants to perceive divergent light signals leading to adaptive changes in response to differing environmental conditions. However, the mechanism of light signal transduction is not fully understood. Here we report the identification of a new signaling intermediate from Arabidopsis thaliana, Scarecrow-like (SCL)13, which serves as a positive regulator of continuous red light signals downstream of phytochrome B (phyB). SCL13 antisense lines exhibit reduced sensitivity towards red light, but only a distinct subset of phyB-mediated responses is affected, indicating that SCL13 executes its major role in hypocotyl elongation during de-etiolation. Genetic evidence suggests that SCL13 is also needed to modulate phytochrome A (phyA) signal transduction in a phyB-independent way. The SCL13 protein is localized in the cytoplasm, but can also be detected in the nucleus. Overexpression of both a nuclear and cytoplasmic localized SCL13 protein leads to a hypersensitive phenotype under red light indicating that SCL13 is biologically active in both compartments. SCL13 is a member of the plant-specific GRAS protein family, which is involved in various different developmental and signaling pathways. A previously identified phytochrome A signaling intermediate, PAT1, belongs to the same subbranch of GRAS proteins as SCL13. Although both proteins are involved in phytochrome signaling, each is specific for a different light condition and regulates a different subset of responses.

Over‐expression of SOB5 suggests the involvement of a novel plant protein in cytokinin‐mediated development

Cytokinins are a class of phytohormones that play a critical role in plant growth and development. sob5-D, an activation-tagging mutant, shows phenotypes typical of transgenic plants expressing the Agrobacterium tumefaciens isopentenyltransferase (ipt) gene that encodes the enzyme catalyzing the first step of cytokinin biosynthesis. The sob5-D mutant phenotypes are caused by over-expression of a novel gene, SOB5. Sequence analysis places SOB5 in a previously uncharacterized family of plant-specific proteins. A translational fusion between SOB5 and the green fluorescent protein reporter was localized in the cytoplasm as well as associated with the plasma membrane when transiently expressed in onion epidermal cells. Analysis of transgenic plants harboring an SOB5:SOB5-beta-glucuronidase (GUS) translational fusion under the control of the SOB5 promoter region showed GUS activity in vegetative tissues (hydathodes and trichomes of leaves, shoot meristems and roots) as well as in floral tissues (pistil tips, developing anthers and sepal vasculature). Cytokinin quantification analysis revealed that adult sob5-D plants accumulated higher levels of trans-zeatin riboside, trans-zeatin riboside monophosphate and isopentenyladenine 9-glucoside when compared to the wild-type. Consistent with this result, AtIPT3 and AtIPT7 were found to be up-regulated in a tissue-specific manner in sob5-D mutants. Physiological analysis of the sob5-D mutant demonstrated reduced responsiveness to exogenous cytokinin in both root-elongation and callus-formation assays. Taken together, our data suggest a role for the novel gene SOB5 in cytokinin-mediated plant development.

Osdof28: A New Member of the DOF Transcription Factor Family from Rice

DOF is a novel family of plant-specific proteins that share a unique and highly conserved DNA binding domain with one CX 2CX 21CX 2C zinc finger motif. In this study, the Osdof28 gene, which codes a characteristic amino acid sequence of the DOF transcription factor family, was screened from rice ( Oryza sativa japonica) using a yeast one-hybrid assay. Great amounts of the Osdof28 transcripts were found to accumulate in stems and leaves, with less in the roots, and no detectable transcription found in the germs. Osdof28 can be induced by salicylic acid and INA, which suggests that it may be related to the plant systemic acquired resistance (SAR). The relationship was confirmed through biological induction of SAR using Xanthomonascampestrispv. oryzae, with more expression of Osdof28 observed in the systemic tissues after infection.

Identification of a novel family of 70 kDa microtubule‐associated proteins in Arabidopsis cells

Most plant microtubule-associated proteins (MAPs) have homologues across the phylogenetic spectrum. To find potential plant-specific MAPs that will have evaded bioinformatic searches we devised a low stringency method for isolating proteins from an Arabidopsis cell suspension on endogenous taxol-microtubules. By tryptic peptide mass fingerprinting we identified 55 proteins that were enriched on taxol-microtubules. Amongst a range of known MAPs, such as kinesins, MAP65 isoforms and MOR1, we detected 'unknown' 70 kDa proteins that belong to a family of five closely related Arabidopsis proteins having no known homologues amongst non-plant organisms. To verify that AtMAP70-1 associates with microtubules in vivo, it was expressed as a GFP fusion. This confirmed that the protein decorates all four microtubule arrays in both transiently infected Arabidopsis and stably transformed tobacco BY-2 suspension cells. Microtubule-directed drugs perturbed the localization of AtMAP70-1 but cytochalasin D did not. AtMAP70-1 contains four predicted coiled-coil domains and truncation studies identified a central domain that targets the fusion protein to microtubules in vivo. This study therefore introduces a novel family of plant-specific proteins that interact with microtubules.

A central role of Arabidopsis thaliana ovate family proteins in networking and subcellular localization of 3-aa loop extension homeodomain proteins

The organization of living cells is based on networks of interacting molecules. Systematic analysis of protein interactions of 3-aa loop extension (TALE) homeodomain proteins, fundamental regulators of plant meristem function and leaf development, revealed a highly connected, complex network. The network includes nine members of Arabidopsis thaliana ovate family proteins (AtOFPs), a plant-specific protein family, indicating a close functional connection to TALE homeodomain proteins. Evidence is provided that AtOFP1 is an essential pleiotropic developmental regulator. AtOFP1 and AtOFP5 are shown to associate with the cytoskeleton and to regulate subcellular localization of TALE homeodomain proteins, suggesting a previously unrecognized control mechanism in plant development.