Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK; Institute for Sustainable Plant Protection, National Research Council of Italy, Via Madonna del Piano 10, Sesto Fiorentino, 50019, Florence, Italy.
Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK.
J Plant Physiol. 2021 Sep;264:153470. doi: 10.1016/j.jplph.2021.153470. Epub 2021 Jul 8.
After an episode of heat stress plants retain a cellular "memory" of this event, a phenomenon known as thermomemory. This mechanism allows plants to better cope against a subsequent heat event. Thermomemory occurs through the persistence of heat shock proteins (HSPs) synthesized after the first "priming" event. Maintenance of this thermomemory comes at the cost to growth though, therefore it is vital that the memory is reset when no longer required. Recently, it has been reported that autophagy is important for resetting the thermomemory. It has also been shown recently that in response to heat, Arabidopsis displays an increase in chloroplast free calcium concentration which is partially dependent on calcium sensing receptor (CAS) protein. It is not known what the purpose of this heat-activated calcium signal is. Therefore, we compared downstream responses to heat in wild type (WT) and cas mutants, as the latter produce a reduced chloroplast calcium signal to heat. We found that after thermopriming the cas mutants displayed a greater biomass and a reduced level of the small heat shock protein HSP 17.6 degradation compared to WT. cas mutants did not show an increase in free amino acid levels after thermopriming, suggesting reduced autophagy. These results suggest that heat-induced chloroplast calcium elevation is a positive signal for resetting of the thermomemory.
在经历一次热应激后，植物会保留对该事件的细胞“记忆”，这一现象被称为热记忆。这种机制使植物能够更好地应对随后的热应激。热记忆通过在第一次“引发”事件后合成的热休克蛋白 (HSP) 的持续存在而发生。尽管如此，维持这种热记忆是以牺牲生长为代价的，因此当不再需要时，必须重置记忆。最近，有报道称自噬对于重置热记忆很重要。最近还表明，在响应热时，拟南芥显示叶绿体游离钙浓度增加，这部分依赖于钙感应受体 (CAS) 蛋白。目前尚不清楚这种热激活钙信号的目的是什么。因此，我们比较了 WT 和 cas 突变体在热胁迫后的下游响应，因为后者对热产生的叶绿体钙信号降低。我们发现，与 WT 相比，热预培养后 cas 突变体的生物量更大，小热休克蛋白 HSP 17.6 的降解水平更低。cas 突变体在热预培养后没有出现游离氨基酸水平的增加，表明自噬减少。这些结果表明，热诱导的叶绿体钙升高是重置热记忆的正向信号。
