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

The protein kinase family of enzymes mediates the responses of eukaryotic cells to both inter- and intracellular signals. These enzymes are either serine/threonine-specific or tyrosine-specific. Many of the latter are transmembrane receptors and are important in transduction of extracellular signals across the plasma membrane, whereas few examples of receptor serine kinases have been reported. We have now identified a complementary DNA clone from Zea mays (L.) encoding a putative serine/threonine-specific protein kinase structurally related to the receptor tyrosine kinases. This structural similarity is evidence for a previously undescribed class of transmembrane receptor in higher plants likely to be involved in signal reception and transduction. Furthermore, the catalytic domain of this protein kinase is linked through a transmembrane domain to an extracellular domain similar to that of glycoproteins encoded in the self-incompatibility locus of Brassica which are involved in the self-recognition system between pollen and stigma.
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PMID:Relationship of a putative receptor protein kinase from maize to the S-locus glycoproteins of Brassica. 216 28

ARK1 is a vegetatively expressed receptor protein kinase gene isolated from Arabidopsis thaliana based on its sequence similarity to Brassica genes involved in pollen-stigma signaling and the self-incompatibility response. This paper shows that the kinase domain of ARK1 autophosphorylates on serine and threonine residues when expressed as a recombinant fusion protein. ARK1 produces a 2.9 kb transcript encoding a transmembrane receptor protein kinase and a 1.4 kb transcript encoding the receptor domain alone. Constitutive high-level expression of ARK1 transcripts in transgenic Arabidopsis resulted in severe stunting and also disrupted normal cellular expansion and differentiation.
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PMID:An S-locus-related gene in Arabidopsis encodes a functional kinase and produces two classes of transcripts. 881 66

To gain further insight into the mode of action of S-locus receptor kinase (SRK), a receptor-like kinase involved in the self-incompatibility response in Brassica, different recombinant SRK proteins have been expressed in a membranous environment using the insect cell/baculovirus system. Recombinant SRK proteins exhibited properties close to those of the endogenous stigmatic SRK protein and were found to autophosphorylate on serine and threonine residues in insect cell microsomes. Autophosphorylation was constitutive because it did not require the presence of pollen or stigma extracts in the phosphorylation buffer. Phosphorylation was shown to occur in trans, suggesting the existence of constitutive homooligomers of membrane-anchored recombinant SRK. To investigate the physiological relevance of these results, we have examined the oligomeric status of SRK in planta in cross-linking experiments and by velocity sedimentation on sucrose gradients. Our data strongly suggest that SRK is associated both with other SRK molecules and other stigma proteins in nonpollinated flowers. These findings may have important implications for our understanding of self-pollen signaling.
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PMID:The integral membrane S-locus receptor kinase of Brassica has serine/threonine kinase activity in a membranous environment and spontaneously forms oligomers in planta. 1072 90

Applying 10 pmol of okadaic acid (OA), a specific inhibitor of type 1 or type 2A serine/threonine protein phosphatases, to the orchid (Phalaenopsis species) stigma induced a dramatic increase in ethylene production and an accelerated senescence of the whole flower. Aminoethoxyvinylglycine or silver thiosulfate, inhibitors of ethylene biosynthesis or action, respectively, effectively inhibited the OA-induced ethylene production and retarded flower senescence, suggesting that the protein phosphatase inhibitor induced orchid flower senescence through an ethylene-mediated signaling pathway. OA treatment induced a differential expression pattern for the 1-aminocyclopropane-1-carboxylic acid synthase multigene family. Accumulation of Phal-ACS1 transcript in the stigma, labelum, and ovary induced by OA were higher than those induced by pollination as determined by "semiquantitative" reverse transcriptase-polymerase chain reaction. In contrast, the transcript levels of Phal-ACS2 and Phal-ACS3 induced by OA were much lower than those induced by pollination. Staurosporine, a protein kinase inhibitor, on the other hand, inhibited the OA-induced Phal-ACS1 expression in the stigma and delayed flower senescence. Our results suggest that a hyper-phosphorylation status of an unidentified protein(s) is involved in up-regulating the expression of Phal-ACS1 gene resulting in increased ethylene production and accelerated the senescence process of orchid flower.
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PMID:Differential expression of 1-aminocyclopropane-1-carboxylate synthase genes during orchid flower senescence induced by the protein phosphatase inhibitor okadaic acid. 1135 Oct 88

We have examined the effect of the protein phosphatase inhibitors okadaic acid and microcystin on pollen-pistil interactions in Brassica. Inhibitor-treated flowers or floral buds were pollinated with untreated pollen and examined for pollen tube growth by fluorescence microscopy. Our results show that type 1 or type 2A serine/threonine phosphatases play a crucial role in the pollination responses of Brassica. We observed two distinct effects of protein phosphatase inhibitors on pollination: (a) the inhibition of pollen tube growth during cross-pollination in flowers, and (b) the break-down of self-incompatibility or promotion of pollen tube growth during self-pollination in flower buds just prior to anthesis. Thus, treatment of flower pistils with protein phosphatase inhibitors resulted in the inhibition of pollen tube growth at the surface of the papillar cells of the stigma in crosses between different self-incompatible Brassica oleracea strains, in an interspecific cross between B. oleracea and Brassica campestris, and in self-pollinations of a self-fertile Brassica napus cultivar. With four different self-incompatibility genotypes, treatment of mature flowers with protein phosphatase inhibitors had no effect on self-pollination response. In contrast, treatment of flower buds just prior to the anthesis stage allowed self-pollen tube invasion of papillar cells. However, the magnitude of this effect was genotype dependent, being most pronounced in the S22 genotype. The data support the conclusion that pollinations in Brassica are controlled in part by the presence of phosphorylated proteins in the papillar cells of the stigma, and that the quantity of these proteins or their levels of phosphorylation changes during stigma development.
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PMID:Effects of Inhibitors of Protein Serine/Threonine Phosphatases on Pollination in Brassica. 1223 9