A heat‐activated calcium‐permeable channel – Arabidopsis cyclic nucleotide‐gated ion channel 6 – is involved in heat shock responses

Abstract

SUMMARYAn increased concentration of cytosolic calcium ions (Ca 2+ ) is an early response by plant cells to heat shock.However, the molecular mechanism underlying the heat-induced initial Ca 2+ response in plants is unclear. In this study, we identified and characterized a heat-activated Ca 2+-permeable channel in the plasma membrane of Arabidopsis thaliana root protoplasts using reverse genetic analysis and the whole-cell patch-clamp technique. The results indicated that A. thaliana cyclic nucleotide-gated ion channel 6 (CNGC6) mediates heatinduced Ca 2+ influx and facilitates expression of heat shock protein (HSP) genes and the acquisition of thermotolerance. GUS and GFP reporter assays showed that CNGC6 expression is ubiquitous in A. thaliana, and the protein is localized to the plasma membrane of cells. Furthermore, it was found that the level of cytosolic cAMP was increased by a mild heat shock, that CNGC6 was activated by cytosolic cAMP, and that exogenous cAMP promoted the expression of HSP genes. The results reveal the role of cAMP in transduction of heat shock signals in plants. The correlation of an increased level of cytosolic cAMP in a heat-shocked plant with activation of the Ca 2+ channels and downstream expression of HSP genes sheds some light on how plants transduce a heat stimulus into a signal cascade that leads to a heat shock response.

Plasma Membrane Cyclic Nucleotide Gated Calcium Channels Control Land Plant Thermal Sensing and Acquired Thermotolerance

“…The thermosensory function was confirmed by targeted mutagenesis of CNGCb and by analyzing acquired thermotolerance in the dnd1 and dnd2 mutants: CNGCb, CNGC2, and CNGC4 were found to be major regulatory components of the land plant thermosensory machinery controlling the HSR and acquired thermotolerance. Strengthening this finding, CNGC6 was recently found to be involved in tissuespecific thermosensing, Hsp expression, and Arabidopsis thermotolerance (Gao et al, 2012). This is not unexpected given that phylogeny places CNGC6 in a seed plant-specific clade, which stemmed from the ancestral thermosensory clade.…”

“…Hsps sometimes accumulate in various plant tissues under isothermal conditions (Saidi et al, 2005;Finka et al, 2011), for example, in response to phytohormones, such as abscisic acid (Snyman and Cronjé, 2008), pollutants (Saidi et al, 2007), or when exposed to combinations of mild heat and dehydration stresses (Rizhsky et al, 2004). It is tempting to speculate that the thermosensory CNGC2 and CNGC4, either on their own or in combination with more distantly related CNGCs, such as CNGC6 (Gao et al, 2012), form heteromeric Ca 2+ channels that can trigger Hsp expression at constant temperature and, as such, mediate plant resistances to various environmental stresses in addition to thermotolerance.…”

A Cyclic Nucleotide-Gated Channel (CNGC16) in Pollen Is Critical for Stress Tolerance in Pollen Reproductive Development

“…In the first, a knockout of AtCNGC6 in Arabidopsis resulted in plants with vegetative tissues showing a decreased tolerance to heat stress (Gao et al, 2012). This appears analogous to the increased heat stress sensitivity observed here for cngc16 pollen.…”

“…Recently, cNMPs have also been linked to heat stress responses in vegetative tissues from Arabidopsis (Arabidopsis thaliana) and the moss Physcomitrella patens (Finka et al, 2012;Gao et al, 2012). In these cases, genetic and electrophysiological evidence suggest that cNMPs activate cyclic nucleotide-gated ion channels (CNGCs).…”

Main Stages of Plant Cellular Response to Heat Stress

“…Изменения в ци-тоскелете вкупе с перестройками липидного бислоя мембран влекут за собой открытие спе-цифических кальциевых каналов, расположен-ных в плазмалемме, и последующее поступле-ние ионизированного кальция из межклеточ-ного пространства в клетку [Saidi et al, 2009;Lin et al, 2014;Рихванов и др., 2014]. Повышение концентрации ионов кальция в цитоплазме клеток растений (при-близительно в 2-4 раза по сравнению с обыч-ными условиями) при высокотемпературном воздействии происходит очень быстро, напри-мер, в цитоплазме клеток A. thaliana или у мха P. patens в течение 3-5 минут от начала повы-шения температуры [Saidi et al, 2009;Finka et al, 2012;Gao et al, 2012]. Но через корот-кое время (несколько минут) уровень кальция в цитозоле начинает снижаться, даже если вы-сокая температура продолжает действовать [Saidi et al, 2009;Finka et al, 2012].…”