@article{DindasDreyerHuangetal.2021,
  author    = {Dindas, Julian and Dreyer, Ingo and Huang, Shouguang and Hedrich, Rainer and Roelfsema, M. Rob G.},
  title     = {A voltage-dependent Ca\(^{2+}\) homeostat operates in the plant vacuolar membrane},
  series = {New Phytologist},
  volume    = {230},
  journal   = {New Phytologist},
  number    = {4},
  doi       = {10.1111/nph.17272},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-259627},
  pages     = {1449-1460},
  year      = {2021},
  abstract  = {Cytosolic calcium signals are evoked by a large variety of biotic and abiotic stimuli and play an important role in cellular and long distance signalling in plants. While the function of the plasma membrane in cytosolic Ca\(^{2+}\) signalling has been intensively studied, the role of the vacuolar membrane remains elusive. A newly developed vacuolar voltage clamp technique was used in combination with live-cell imaging, to study the role of the vacuolar membrane in Ca\(^{2+}\) and pH homeostasis of bulging root hair cells of Arabidopsis. Depolarisation of the vacuolar membrane caused a rapid increase in the Ca\(^{2+}\) concentration and alkalised the cytosol, while hyperpolarisation led to the opposite responses. The relationship between the vacuolar membrane potential, the cytosolic pH and Ca2+ concentration suggests that a vacuolar H\(^{+}\)/Ca\(^{2+}\) exchange mechanism plays a central role in cytosolic Ca2+ homeostasis. Mathematical modelling further suggests that the voltage-dependent vacuolar Ca\(^{2+}\) homeostat could contribute to calcium signalling when coupled to a recently discovered K\(^{+}\) channel-dependent module for electrical excitability of the vacuolar membrane.},
  language  = {en}
}
@article{JaślanDreyerLuetal.2019,
  author    = {Jaślan, Dawid and Dreyer, Ingo and Lu, Jinping and O'Malley, Ronan and Dindas, Julian and Marten, Irene and Hedrich, Rainer},
  title     = {Voltage-dependent gating of SV channel TPC1 confers vacuole excitability},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-019-10599-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-202029},
  pages     = {2659},
  year      = {2019},
  abstract  = {In contrast to the plasma membrane, the vacuole membrane has not yet been associated with electrical excitation of plants. Here, we show that mesophyll vacuoles from Arabidopsis sense and control the membrane potential essentially via the K\(^+\)-permeable TPC1 and TPK channels. Electrical stimuli elicit transient depolarization of the vacuole membrane that can last for seconds. Electrical excitability is suppressed by increased vacuolar Ca\(^{2+}\) levels. In comparison to wild type, vacuoles from the fou2 mutant, harboring TPC1 channels insensitive to luminal Ca\(^{2+}\), can be excited fully by even weak electrical stimuli. The TPC1-loss-of-function mutant tpc1-2 does not respond to electrical stimulation at all, and the loss of TPK1/TPK3-mediated K\(^{+}\) transport affects the duration of TPC1-dependent membrane depolarization. In combination with mathematical modeling, these results show that the vacuolar K\(^+\)-conducting TPC1 and TPK1/TPK3 channels act in concert to provide for Ca\(^{2+}\)- and voltage-induced electrical excitability to the central organelle of plant cells.},
  language  = {en}
}
@article{DindasScherzerRoelfsemaetal.2018,
  author    = {Dindas, Julian and Scherzer, S{\"o}nke and Roelfsema, M. Rob G. and Meyer, Katharina von and M{\"u}ller, Heike M. and Al-Rasheid, K. A. S. and Palme, Klaus and Dietrich, Petra and Becker, Dirk and Bennett, Malcolm J. and Hedrich, Rainer},
  title     = {AUX1-mediated root hair auxin influx governs SCFTIR1/AFB-type Ca2+ signaling},
  series = {Nature Communications},
  volume    = {9},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-018-03582-5},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225368},
  year      = {2018},
  abstract  = {Auxin is a key regulator of plant growth and development, but the causal relationship between hormone transport and root responses remains unresolved. Here we describe auxin uptake, together with early steps in signaling, in Arabidopsis root hairs. Using intracellular microelectrodes we show membrane depolarization, in response to IAA in a concentration- and pH-dependent manner. This depolarization is strongly impaired in aux1 mutants, indicating that AUX1 is the major transporter for auxin uptake in root hairs. Local intracellular auxin application triggers Ca2+ signals that propagate as long-distance waves between root cells and modulate their auxin responses. AUX1-mediated IAA transport, as well as IAA- triggered calcium signals, are blocked by treatment with the SCFTIR1/AFB - inhibitor auxinole. Further, they are strongly reduced in the tir1afb2afb3 and the cngc14 mutant. Our study reveals that the AUX1 transporter, the SCFTIR1/AFB receptor and the CNGC14 Ca2+ channel, mediate fast auxin signaling in roots.},
  language  = {en}
}