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

Self-incompatibility in Brassica refers to the rejection of self-related pollen and is mediated by a receptor protein kinase localized to the plasma membrane of the stigma epidermis in the flower. The recessive mutation mod eliminates self-incompatibility in the stigma. In mod mutants, self-compatibility was shown to be associated with the absence of transcripts encoded by an aquaporin-related gene. This observation suggests that a water channel is required for the self-incompatibility response of Brassica, which is consistent with the concept that regulation of water transfer from the stigma to pollen is a checkpoint in the early events of pollination in the crucifer family.
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PMID:An aquaporin-like gene required for the Brassica self-incompatibility response. 917 Oct 60

There is strong evidence that aquaporins are central components in plant water relations. Plant species possess more aquaporin genes than species from other kingdoms. According to sequence similarities, four major groups have been identified, which can be further divided into subgroups that may correspond to localization and transport selectivity. They may be involved in compatible solute distribution, gas-transfer (CO2, NH3) as well as in micronutrient uptake (boric acid). Recent advances in determining the structure of some aquaporins gives further details on the mechanism of selectivity. Gating behaviour of aquaporins is poorly understood but evidence is mounting that phosphorylation, pH, pCa and osmotic gradients can affect water channel activity. Aquaporins are enriched in zones of fast cell division and expansion, or in areas where water flow or solute flux density would be expected to be high. This includes biotrophic interfaces between plants and parasites, between plants and symbiotic bacteria or fungi, and between germinating pollen and stigma. On a cellular level aquaporin clusters have been identified in some membranes. There is also a possibility that aquaporins in the endoplasmic reticulum may function in symplasmic transport if water can flow from cell to cell via the desmotubules in plasmodesmata. Functional characterization of aquaporins in the native membrane has raised doubt about the conclusiveness of expression patterns alone and need to be conducted in parallel. The challenge will be to elucidate gating on a molecular level and cellular level and to tie those findings into plant water relations on a macroscopic scale where various flow pathways need to be considered.
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PMID:Plant aquaporins: multifunctional water and solute channels with expanding roles. 1184 62