Chloroplasts are central to solar light harvesting and photosynthesis. Optimal chloroplast functioning is vitally dependent on a very intensive traffic of metabolites and ions between the cytosol and stroma, and shoul...Chloroplasts are central to solar light harvesting and photosynthesis. Optimal chloroplast functioning is vitally dependent on a very intensive traffic of metabolites and ions between the cytosol and stroma, and should be attuned for adverse environmental conditions. This is achieved by an orchestrated regulation of a variety of transport systems located at chloroplast membranes such as porines, solute channels, ion-specific cation and anion channels, and various primary and secondary active transport systems. In this review we describe the molecular nature and functional properties of the inner and outer envelope and thylakoid membrane channels and transporters. We then discuss how their orchestrated regulation affects thylakoid structure, electron transport and excitation energy transfer, proton-motive force partition, ion homeostasis, stromal pH regulation, andvolume regulation. We link the activity of key cation and anion transport systems with stress-specific signaling processes in chloroplasts, and discuss how these signals interact with the signals generated in other organelles to optimize the cell performance, with a special emphasis on Ca^2＋ and reactive oxygen species signaling.展开更多
Two-pore cation channel,TPC1,is ubiquitous in the vacuolar membrane of terrestrial plants and mediates the long distance signaling upon biotic and abiotic stresses.It possesses a wide pore,which transports small mono-...Two-pore cation channel,TPC1,is ubiquitous in the vacuolar membrane of terrestrial plants and mediates the long distance signaling upon biotic and abiotic stresses.It possesses a wide pore,which transports small mono-and divalent cations.K^(+) is transported more than 10-fold faster than Ca^(2+) ,which binds with a higher affinity within the pore.Key pore residues,responsible for Ca^(2+) binding,have been recently identified.There is also a substantial pro-gress in the mechanistic and structural understanding of the plant TPC1 gating by membrane voltage and cytosolic and luminal Ca^(2+).Collectively,these gating factors at resting conditions strongly reduce the potentially lethal Ca^(2+) leak from the vacuole.Such tight control is impressive,bearing in mind high unitary conductance of the TPC1 and its abundance,with thousands of active channel copies per vacuole.But it remains a mystery how this high thresh-old is overcome upon signaling,and what type of signal is emitted by TPC1,whether it is Ca^(2+)or electrical one,or a transduction via protein conformational change,independent on ion conductance.Here we discuss non-exclusive scenarios for the TPC1 integration into Ca^(2+),ROS and electrical signaling.展开更多
文摘Chloroplasts are central to solar light harvesting and photosynthesis. Optimal chloroplast functioning is vitally dependent on a very intensive traffic of metabolites and ions between the cytosol and stroma, and should be attuned for adverse environmental conditions. This is achieved by an orchestrated regulation of a variety of transport systems located at chloroplast membranes such as porines, solute channels, ion-specific cation and anion channels, and various primary and secondary active transport systems. In this review we describe the molecular nature and functional properties of the inner and outer envelope and thylakoid membrane channels and transporters. We then discuss how their orchestrated regulation affects thylakoid structure, electron transport and excitation energy transfer, proton-motive force partition, ion homeostasis, stromal pH regulation, andvolume regulation. We link the activity of key cation and anion transport systems with stress-specific signaling processes in chloroplasts, and discuss how these signals interact with the signals generated in other organelles to optimize the cell performance, with a special emphasis on Ca^2＋ and reactive oxygen species signaling.
文摘Two-pore cation channel,TPC1,is ubiquitous in the vacuolar membrane of terrestrial plants and mediates the long distance signaling upon biotic and abiotic stresses.It possesses a wide pore,which transports small mono-and divalent cations.K^(+) is transported more than 10-fold faster than Ca^(2+) ,which binds with a higher affinity within the pore.Key pore residues,responsible for Ca^(2+) binding,have been recently identified.There is also a substantial pro-gress in the mechanistic and structural understanding of the plant TPC1 gating by membrane voltage and cytosolic and luminal Ca^(2+).Collectively,these gating factors at resting conditions strongly reduce the potentially lethal Ca^(2+) leak from the vacuole.Such tight control is impressive,bearing in mind high unitary conductance of the TPC1 and its abundance,with thousands of active channel copies per vacuole.But it remains a mystery how this high thresh-old is overcome upon signaling,and what type of signal is emitted by TPC1,whether it is Ca^(2+)or electrical one,or a transduction via protein conformational change,independent on ion conductance.Here we discuss non-exclusive scenarios for the TPC1 integration into Ca^(2+),ROS and electrical signaling.
