TY  - JOUR
A1  - Voss, Lena J.
A1  - McAdam, Scott A. M.
A1  - Knoblauch, Michael
A1  - Rathje, Jan M.
A1  - Brodribb, Tim
A1  - Hedrich, Rainer
A1  - Roelfsema, M. Rob G.
T1  - Guard cells in fern stomata are connected by plasmodesmata, but control cytosolic Ca2+ levels autonomously
JF  - New Phytologist
N2  - Recent studies have revealed that some responses of fern stomata to environmental signals differ from those of their relatives in seed plants. However, it is unknown whether the biophysical properties of guard cells differ fundamentally between species of both clades.

Intracellular micro-electrodes and the fluorescent Ca2+ reporter FURA2 were used to study voltage-dependent cation channels and Ca2+ signals in guard cells of the ferns Polypodium vulgare and Asplenium scolopendrium.

Voltage clamp experiments with fern guard cells revealed similar properties of voltage-dependent K+ channels as found in seed plants. However, fluorescent dyes moved within the fern stomata, from one guard cell to the other, which does not occur in most seed plants. Despite the presence of plasmodesmata, which interconnect fern guard cells, Ca2+ signals could be elicited in each of the cells individually.

Based on the common properties of voltage-dependent channels in ferns and seed plants, it is likely that these key transport proteins are conserved in vascular plants. However, the symplastic connections between fern guard cells in mature stomata indicate that the biophysical mechanisms that control stomatal movements differ between ferns and seed plants.
KW  - calcium signals
KW  - ferns
KW  - guard cell
KW  - plasmodesmata
KW  - potassium channels
KW  - seed plants
KW  - stomata
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-233247
VL  - 219
ER  - 
TY  - JOUR
A1  - Graus, Dorothea
A1  - Li, Kunkun
A1  - Rathje, Jan M.
A1  - Ding, Meiqi
A1  - Krischke, Markus
A1  - Müller, Martin J.
A1  - Cuin, Tracey Ann
A1  - Al‐Rasheid, Khaled A. S.
A1  - Scherzer, Sönke
A1  - Marten, Irene
A1  - Konrad, Kai R.
A1  - Hedrich, Rainer
T1  - Tobacco leaf tissue rapidly detoxifies direct salt loads without activation of calcium and SOS signaling
JF  - New Phytologist
N2  - Salt stress is a major abiotic stress, responsible for declining agricultural productivity. Roots are regarded as hubs for salt detoxification, however, leaf salt concentrations may exceed those of roots. How mature leaves manage acute sodium chloride (NaCl) stress is mostly unknown.

To analyze the mechanisms for NaCl redistribution in leaves, salt was infiltrated into intact tobacco leaves. It initiated pronounced osmotically‐driven leaf movements. Leaf downward movement caused by hydro‐passive turgor loss reached a maximum within 2 h.

Salt‐driven cellular water release was accompanied by a transient change in membrane depolarization but not an increase in cytosolic calcium ion (Ca\(^{2+}\)) level. Nonetheless, only half an hour later, the leaves had completely regained turgor. This recovery phase was characterized by an increase in mesophyll cell plasma membrane hydrogen ion (H\(^{+}\)) pumping, a salt uptake‐dependent cytosolic alkalization, and a return of the apoplast osmolality to pre‐stress levels. Although, transcript numbers of abscisic acid‐ and Salt Overly Sensitive pathway elements remained unchanged, salt adaptation depended on the vacuolar H\(^{+}\)/Na\(^{+}\)‐exchanger NHX1.

Altogether, tobacco leaves can detoxify sodium ions (Na\(^{+}\)) rapidly even under massive salt loads, based on pre‐established posttranslational settings and NHX1 cation/H+ antiport activity. Unlike roots, signaling and processing of salt stress in tobacco leaves does not depend on Ca\(^{2+}\) signaling.
KW  - calcium signaling
KW  - cytosolic pH
KW  - leaf response
KW  - NaCl transport
KW  - NHX1
KW  - osmotic effects
KW  - Salt Overly Sensitive pathway
KW  - salt stress
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312152
VL  - 237
IS  - 1
SP  - 217
EP  - 231
ER  -