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Query: UMLS:C0277787 (stigma)
 13,352 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pollen tube adhesion and guidance on extracellular matrices within the pistil are essential processes that convey the pollen tube cell and the sperm cells to the ovule. In this study, we purified an additional molecule from the pistil that enhances pollen tube adhesion when combined with the SCA (stigma/stylar cysteine-rich adhesin)/pectin matrix in our in vitro assay. The enhancer of adhesion was identified as free ubiquitin (Ub). This was confirmed by use of bovine Ub as a substitute for lily (Lilium longiflorum Thunb.) stigma Ub. To study the interaction of SCA and Ub with the lily pollen tube, we labeled both proteins with biotin. We observed uptake of biotin-labeled SCA and Ub into the pollen tube cells in vitro using confocal microscopy. For SCA, a strong signal occurred first at the tip of the pollen tube, suggestive of an endocytosis event, and then progressively throughout the tube cytoplasm. SCA was also localized inside the in vivo pollen tube using immunogold electron microscopy and found to be present in endosomes, multivesicular bodies, and vacuoles, all known to be endocytic compartments. It was also confirmed that SCA is endocytosed in the in vitro adhesion assay. Internalization of SCA was increased in pollen tubes treated with exogenous Ub compared to those without Ub, suggesting that Ub may facilitate SCA endocytosis. These results show that Ub can act as an enhancer of pollen tube adhesion in vitro and that it is taken up into the pollen tube as is SCA. The Ub machinery may play a role in pollen tube adhesion and guidance in lily.
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PMID:Exogenous free ubiquitin enhances lily pollen tube adhesion to an in vitro stylar matrix and may facilitate endocytosis of SCA. 1699 86

A cotton fiber cDNA, GhRING1, and its corresponding gene have been cloned and characterized. The GhRING1 gene encodes a RING-type ubiquitin ligase (E3) containing 338 amino acids (aa). The GhRING1 protein contains a RING finger motif with conserved cysteine and histine residues at the C-terminus, and is classified as a C(3)H(2)C(3)-type RING protein. Blast searches show that GhRING1 has the highest homology to At3g19950, a zinc finger family protein from Arabidopsis. Real time RT-PCR analysis indicates that the GhRING1 gene is expressed in cotton fibers in a developmental manner. The transcript level of GhRING1 gene reaches a maximum in elongating fibers at 15 days post-anthesis (DPA). In vitro auto-ubiquitination assays using wheat germ extract and a reconstitution system demonstrate that GhRING1 has the ubiquitin E3 ligase activity. The histochemical GUS assay was performed to analyze tissue specificity of the GhRING1 and At3g19950 promoters in transgenic Arabidopsis plants. The GUS assay shows that the promoter of At3g19950 is highly activated in leaves, roots, trichomes, and also in anthers and stigma of flowers. In contrast, the GUS expression directed by the GhRING1 promoter is only located at stipules and anthers. The expression pattern of GhRING1 suggests that protein ubiquitination and turnover may be involved in transition to different stages of cotton fiber development.
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PMID:Characterization and promoter analysis of a cotton RING-type ubiquitin ligase (E3) gene. 2037 76

The self-pollination barrier of self-incompatibility in the Brassicaceae is based on the activity of a polymorphic stigma receptor and its pollen ligand, whose allele-specific interaction triggers a signaling cascade within the stigma epidermal cell that culminates in the inhibition of pollen tube development. Recent analyses have identified signaling intermediates and revealed unexpected cross-talk between self-incompatibility signaling and pistil development. The self-incompatibility response is now thought to be based on a phosphorylation and ubiquitin-mediated degradation pathway that inhibits the secretion of factors required for successful pollination. Because manipulation of the identified signaling intermediates results in only partial disruption of the self-incompatibility reaction, this pathway likely functions in conjunction with other as-yet unidentified signaling pathways to effect complete inhibition of self-pollen.
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PMID:Complex networks of self-incompatibility signaling in the Brassicaceae. 2066 64

Pollination is the first crucial step of sexual reproduction in flowering plants, and it requires communication and coordination between the pollen and the stigma. Maize (Zea mays) is a model monocot with extraordinarily long silks, and a fully sequenced genome, but little is known about the mechanism of its pollen-stigma interactions. In this study, the dynamic gene expression of silks at four different stages before and after pollination was analyzed. The expression profiles of immature silks (IMS), mature silks (MS), and silks at 20 minutes and 3 hours after pollination (20MAP and 3HAP, respectively) were compared. In total, we identified 6,337 differentially expressed genes in silks (SDEG) at the four stages. Among them, the expression of 172 genes were induced upon pollination, most of which participated in RNA binding, processing and transcription, signal transduction, and lipid metabolism processes. Genes in the SDEG dataset could be divided into 12 time-course clusters according to their expression patterns. Gene Ontology (GO) enrichment analysis revealed that many genes involved in microtubule-based movement, ubiquitin-mediated protein degradation, and transport were predominantly expressed at specific stages, indicating that they might play important roles in the pollination process of maize. These results add to current knowledge about the pollination process of grasses and provide a foundation for future studies on key genes involved in the pollen-silk interaction in maize.
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PMID:Transcript profile analyses of maize silks reveal effective activation of genes involved in microtubule-based movement, ubiquitin-dependent protein degradation, and transport in the pollination process. 2330 Oct 84

Seven in absentia (SINA) protein is one subgroup of ubiquitin ligases possessing an N-terminal cysteine-rich really interesting new gene (RING) domain, two zinc-finger motifs, and a C-terminal domain responsible for substrate-binding and dimerization. In tomato (Solanum lycopersicum), the SINA gene family has six members, and we characterize in this study all tomato SINA (SlSINA) genes and the gene products. Our results show that SlSINA genes are differentially regulated in leaf, bud, stem, flower, and root. All SlSINA proteins possess RING-dependent E3 ubiquitin ligase activity, exhibiting similar specificity towards the E2 ubiquitin-conjugating enzyme. SlSINA1/3/4/5/6 are localized in both cytoplasm and nucleus, whereas SlSINA2 is exclusively localized in the nucleus. Moreover, all SlSINAs can interact with each other for homo- or hetero-dimerization. The functionality of SlSINA proteins has been investigated. SlSINA4 plays a positive role in defense signalling, as manifested by elicitation of E3-dependent hypersensitive response-like cell death; the other SlSINAs are negative regulator and capable to suppress hypersensitive response cell death. Transgenic tomato plants overexpressing SlSINA2 exhibit pale-green leaf phenotype, suggesting SlSINA2 regulates chlorophyll level in plant cells, whereas transgenic tomato plants overexpressing SlSINA5 have altered floral structure with exserted stigma, implicating SlSINA5 plays a role in flower development.
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PMID:Functional analysis of the seven in absentia ubiquitin ligase family in tomato. 2932 Jun 7