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  1. ; ; ; ; ; ; ; ; ; ; et al ( , PLOS ONE)
    Caramelli, David (Ed.)
    Full Text Available 
  2. ; ; ; ; ; ; ; ; ( , New Phytologist)
    Summary

    We investigated the molecular basis and physiological implications of anion transport during pollen tube (PT) growth inArabidopsis thaliana(Col‐0).

    Patch‐clamp whole‐cell configuration analysis of pollen grain protoplasts revealed three subpopulations of anionic currents differentially regulated by cytoplasmic calcium ([Ca2+]cyt). We investigated the pollen‐expressed proteinsAtSLAH3,AtALMT12,AtTMEM16 andAtCCCas the putative anion transporters responsible for these currents.

    AtCCC‐GFPwas observed at the shank andAtSLAH3‐GFPat the tip and shank of thePTplasma membrane. Both are likely to carry the majority of anion current at negative potentials, as extracellular anionic fluxes measured at the tip ofPTs with an anion vibrating probe were significantly lower inslah3−/−andccc−/−mutants, but unaffected inalmt12−/−andtmem16−/−. We further characterised the effect ofpHandGABAby patch clamp. Strong regulation by extracellularpHwas observed in the wild‐type, but not intmem16−/−. Our results are compatible withAtTMEM16 functioning as an anion/H+cotransporter and therefore, as a putativepHsensor.GABApresence: (1) inhibited the overall currents, an effect that is abrogated in thealmt12−/−and (2) reduced the current inAtALMT12 transfectedCOS‐7 cells, strongly suggesting the direct interaction ofGABAwithAtALMT12.

    Our data show thatAtSLAH3 andAtCCCactivity is sufficient to explain the major component of extracellular anion fluxes, and unveils a possible regulatory system linkingPTgrowth modulation bypH,GABA, and [Ca2+]cytthrough anionic transporters.

     
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  3. ; ; ; ; ; ; ; ; ; ; et al ( , Plant, Cell & Environment)
    Abstract

    The aquaporin AtPIP2;1 is an abundant plasma membrane intrinsic protein inArabidopsis thalianathat is implicated in stomatal closure, and is highly expressed in plasma membranes of root epidermal cells. When expressed inXenopus laevisoocytes, AtPIP2;1 increased water permeability and induced a non‐selective cation conductance mainly associated with Na+. A mutation in the water pore, G103W, prevented both the ionic conductance and water permeability of PIP2;1. Co‐expression of AtPIP2;1 with AtPIP1;2 increased water permeability but abolished the ionic conductance. AtPIP2;2 (93% identical to AtPIP2;1) similarly increased water permeability but not ionic conductance. The ionic conductance was inhibited by the application of extracellular Ca2+and Cd2+, with Ca2+giving a biphasic dose–response with a prominent IC50of 0.32 mм comparable with a previous report of Ca2+sensitivity of a non‐selective cation channel (NSCC) in Arabidopsis root protoplasts. Low external pH also inhibited ionic conductance (IC50pH 6.8).Xenopusoocytes andSaccharomyces cerevisiaeexpressing AtPIP2;1 accumulated more Na+than controls. Establishing whether AtPIP2;1 has dual ion and water permeabilityin plantawill be important in understanding the roles of this aquaporin and if AtPIP2;1 is a candidate for a previously reported NSCC responsible for Ca2+and pH sensitive Na+entry into roots.

     
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