Free cytosolic Ca^2＋ （[Ca^2＋]cyt） is an ubiquitous second messenger in plant cell signaling, and [Ca^2＋]cyt elevation is associated with Ca^2＋-permeable channels in the plasma membrane and endomembranes regulate...Free cytosolic Ca^2＋ （[Ca^2＋]cyt） is an ubiquitous second messenger in plant cell signaling, and [Ca^2＋]cyt elevation is associated with Ca^2＋-permeable channels in the plasma membrane and endomembranes regulated by a wide range of stimuli. However, knowledge regarding Ca^2＋ channels and their regulation remains limited in planta. A type of voltage- dependent Ca^2＋-permeable channel was identified and characterized for the Vicia faba L. guard cell plasma membrane by using patch-clamp techniques. These channels are permeable to both Ba^2＋ and Ca^2＋, and their activities can be inhibited by micromolar Gd^3＋. The unitary conductance and the reversal potential of the channels depend on the Ca^2＋ or Ba^2＋ gradients across the plasma membrane. The inward whole-cell Ca^2＋ （Ba^2＋） current, as well as the unitary current amplitude and NPo of the single Ca^2＋ channel, increase along with the membrane hyperpolarization. Pharmacological experiments suggest that actin dynamics may serve as an upstream regulator of this type of calcium channel of the guard cell plasma membrane. Cytochalasin D, an actin polymerization blocker, activated the NPo of these channels at the single channel level and increased the current amplitude at the whole-cell level. But these channel activations and current increments could be restrained by pretreatment with an F-actin stabilizer, phalloidin. The potential physiological significance of this regulatory mechanism is also discussed.展开更多
We addressed the existence and localization of integrin-like in guard cells of Vicia faba by using a probe of polyclonal antibody against the human integrin (αvβ3/β5)-Western blot results showed that three integrin...We addressed the existence and localization of integrin-like in guard cells of Vicia faba by using a probe of polyclonal antibody against the human integrin (αvβ3/β5)-Western blot results showed that three integrins-like of about 47.3, 43.7 and 41.1 ku were detected from the preparation of membrane fragments of purified guard cell protoplasts. Further research with immunofluorescent scanning microscopy indicated that those integrins-like were localized on plasma membrane of guard cells, most nearing the dorsal wall, which is consistent with the reception of signals from epidermal cells to guard cells. Thus our results indicate, for the first time, that integrins-like are present at guard cell plasma membrane of Vicia faba.展开更多
Acetyicholine (ACh) is an important neuro-chemical transmitter in animals; it also exists in plants and plays a significant role in various kinds of physiological functions in plants. ACh has been known to induce the ...Acetyicholine (ACh) is an important neuro-chemical transmitter in animals; it also exists in plants and plays a significant role in various kinds of physiological functions in plants. ACh has been known to induce the stomatal opening. By monitoring the changes of cytusolic Ca^2+ with fluorescent probe Fiuo-3 AM under the confocal microscopy, we found that exogenous ACh increased cytosolic Ca^2+ concentration of guard cells of Vicia faba L. Muscarlne, an agonist of muscarine acetyicholine receptor (mAChR), could do so as well. In contrast, atropine, the antagonist of mAChR abolished the ability of ACh to increase Ca^2+ in guard cells. This mechanism is similar to mAChR in animals. When EGTA was used to chelate Ca^2+ or ruthenium red to block Ca^2+ released from vacuole respectively, the results showed that the increased cytosolic Ca^2+ mainly come from intracellular Ca^2+ store. The evidence supports that Ca^2+ is involved in guard-cell response to ACh and that Ca^2+ sigual is coupled to mAChRs in ACh signal transduction in guard cells.展开更多
基金Supported by the National Natural Science Foundation of China (30671029)the State Key Basic Research and Development Plan of China(2006CB100100)
文摘Free cytosolic Ca^2＋ （[Ca^2＋]cyt） is an ubiquitous second messenger in plant cell signaling, and [Ca^2＋]cyt elevation is associated with Ca^2＋-permeable channels in the plasma membrane and endomembranes regulated by a wide range of stimuli. However, knowledge regarding Ca^2＋ channels and their regulation remains limited in planta. A type of voltage- dependent Ca^2＋-permeable channel was identified and characterized for the Vicia faba L. guard cell plasma membrane by using patch-clamp techniques. These channels are permeable to both Ba^2＋ and Ca^2＋, and their activities can be inhibited by micromolar Gd^3＋. The unitary conductance and the reversal potential of the channels depend on the Ca^2＋ or Ba^2＋ gradients across the plasma membrane. The inward whole-cell Ca^2＋ （Ba^2＋） current, as well as the unitary current amplitude and NPo of the single Ca^2＋ channel, increase along with the membrane hyperpolarization. Pharmacological experiments suggest that actin dynamics may serve as an upstream regulator of this type of calcium channel of the guard cell plasma membrane. Cytochalasin D, an actin polymerization blocker, activated the NPo of these channels at the single channel level and increased the current amplitude at the whole-cell level. But these channel activations and current increments could be restrained by pretreatment with an F-actin stabilizer, phalloidin. The potential physiological significance of this regulatory mechanism is also discussed.
基金This work was supported by the Major State Basic Research Program of China (Grant No. G1999011704) and the National Natural Science Foundation of China (Grant No. 39730050).
文摘We addressed the existence and localization of integrin-like in guard cells of Vicia faba by using a probe of polyclonal antibody against the human integrin (αvβ3/β5)-Western blot results showed that three integrins-like of about 47.3, 43.7 and 41.1 ku were detected from the preparation of membrane fragments of purified guard cell protoplasts. Further research with immunofluorescent scanning microscopy indicated that those integrins-like were localized on plasma membrane of guard cells, most nearing the dorsal wall, which is consistent with the reception of signals from epidermal cells to guard cells. Thus our results indicate, for the first time, that integrins-like are present at guard cell plasma membrane of Vicia faba.
文摘Acetyicholine (ACh) is an important neuro-chemical transmitter in animals; it also exists in plants and plays a significant role in various kinds of physiological functions in plants. ACh has been known to induce the stomatal opening. By monitoring the changes of cytusolic Ca^2+ with fluorescent probe Fiuo-3 AM under the confocal microscopy, we found that exogenous ACh increased cytosolic Ca^2+ concentration of guard cells of Vicia faba L. Muscarlne, an agonist of muscarine acetyicholine receptor (mAChR), could do so as well. In contrast, atropine, the antagonist of mAChR abolished the ability of ACh to increase Ca^2+ in guard cells. This mechanism is similar to mAChR in animals. When EGTA was used to chelate Ca^2+ or ruthenium red to block Ca^2+ released from vacuole respectively, the results showed that the increased cytosolic Ca^2+ mainly come from intracellular Ca^2+ store. The evidence supports that Ca^2+ is involved in guard-cell response to ACh and that Ca^2+ sigual is coupled to mAChRs in ACh signal transduction in guard cells.
