2009-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/698169Abstract: The calcium/calmodulin (Ca2+/CaM) transduction pathways participating in early heat shock (HS) response and thermotolerance in rice (Oryza sativa L.) seedlings was investigated. A significant free cytosolic Ca2+ concentration ([Ca2+]cyt) elevation was observed in the root cells during HS. We further showed that Ca2+ ionophore A23187 generates an intense and sustained rise of [Ca2+]cyt in response of HS. In contrast, exogenously supplied a Ca2+ chelator, L-type Ca2+ channel blockers and CaM antagonists were shown severely inhibited [Ca2+]cyt elevation; but not by intracellular Ca2+ release inhibitors. Exogenous application of Ca2+ and A23187 could accelerate CaM1-1 and sHSPC/N (nucleocytoplasmic small heat shock protein) genes expression during early HS response, suggesting that HS induced apoplastic Ca2+ entry through L-type Ca2+ channels into cystol. The sHSP17-type of sHSPC/N gene expression strictly depended on [Ca2+]cyt oscillations that could be decoded by CaM1-1 to transmit early HS signal. We provide evidence that a CaM1-1-GFP fusion protein relocates differentially upon time- and temperature-dependent manner during HS, and demonstrate that overexpression of rice CaM1-1 increased the basal and acquired thermotolerance in Arabidopsis thaliana. These results confirmed that Ca2+ and CaM1-1 are critical for mediating HS signaling during thermotolerance process in rice.Apoplastic Ca2+CalmodulinCytosolic Ca2+ oscillationNucleocytoplasmic sHSPHS signalingThermotolerance