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

To elucidate the role of auxin in flower morphogenesis, its distribution patterns were studied during flower development in Arabidopsis thaliana (L.) Heynh. Expression of DR5::GUS was regarded to reflect sites of free auxin, while immunolocalization with auxin polyclonal antibodies visualized conjugated auxin distribution. The youngest flower bud was loaded with conjugated auxin. During development, the apparent concentration of free auxin increased in gradual patterns starting at the floral-organ tip. Anthers are major sites of high concentrations of free auxin that retard the development of neighboring floral organs in both the acropetal and basipetal directions. The IAA-producing anthers synchronize flower development by retarding petal development and nectary gland activity almost up to anthesis. Tapetum cells of young anthers contain free IAA which accumulates in pollen grains, suggesting that auxin promotes pollen-tube growth towards the ovules. High amounts of free auxin in the stigma induce a wide xylem fan immediately beneath it. After fertilization, the developing embryos and seeds show elevated concentrations of auxin, which establish their axial polarity. This developmental pattern of auxin production during floral-bud development suggests that young organs which produce high concentrations of free IAA inhibit or retard organ-primordium initiation and development at the shoot tip.
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PMID:Role of auxin in regulating Arabidopsis flower development. 1620 86

Although many studies have emphasized the importance of auxin in plant growth and development, the thorough understanding of its effect on pollen-pistil interactions is largely unknown. In this study, we investigated the role of free IAA in pollen-pistil interactions during pollen germination and tube growth in Nicotiana tabacum L. through using histo and subcellular immunolocalization with auxin monoclonal antibodies, quantification by HPLC and ELISA together with GUS staining in DR5::GUS-transformed plants. The results showed that free IAA in unpollinated styles was higher in the apical part and basal part than in the middle part, and it was more abundant in the transmitting tissue (TT). At the stage of pollen germination, IAA reached its highest content in the stigma and was mainly distributed in TT. After the pollen tubes entered the styles, the signal increased in the part where pollen tubes would enter and then rapidly declined in the part where pollen tubes had penetrated. Subcellular localization confirmed the presence of IAA in TT cells of stigmas and styles. Accordingly, a schematic diagram summarizes the changing pattern of free IAA level during flowering, pollination and pollen tube growth. Furthermore, we presented evidence that low concentration of exogenous IAA could, to a certain extent, facilitate in vitro pollen tube growth. These results suggest that IAA may be directly or indirectly involved in the pollen-pistil interactions. Additionally, some improvements of the IAA immunolocalization technique were made.
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PMID:Free IAA in stigmas and styles during pollen germination and pollen tube growth of Nicotiana tabacum. 1848 59

In many angiosperms, outcrossing is enforced by genetic self-incompatibility (SI), which allows cells of the pistil to recognize and specifically inhibit "self" pollen. SI is often associated with increased stigma-anther separation, a morphological trait that promotes cross-pollen deposition on the stigma. However, the gene networks responsible for coordinate evolution of these complex outbreeding devices are not known. In self-incompatible members of the Brassicaceae (crucifers), the inhibition of "self"-pollen is triggered within the stigma epidermal cell by allele-specific interaction between two highly polymorphic proteins, the stigma-expressed S-locus receptor kinase (SRK) and its pollen coat-localized ligand, the S-locus cysteine-rich (SCR) protein. Using Arabidopsis thaliana plants that express SI as a result of transformation with a functional SRK-SCR gene pair, we identify Auxin Response Factor 3 (ARF3) as a mediator of cross-talk between SI signaling and pistil development. We show that ARF3, a regulator of pistil development that is expressed in the vascular tissue of the style, acts non-cell-autonomously to enhance the SI response and simultaneously down-regulate auxin responses in stigma epidermal cells, likely by regulating a mobile signal derived from the stylar vasculature. The inverse correlation we observed in stigma epidermal cells between the strength of SI and the levels of auxin inferred from activity of the auxin-responsive reporter DR5::GUS suggests that the dampening of auxin responses in the stigma epidermis promotes inhibition of "self" pollen in crucifer SI.
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PMID:Non-cell-autonomous regulation of crucifer self-incompatibility by Auxin Response Factor ARF3. 2312 21