The Marine Biological Association of the United Kingdom, The Laboratory, Plymouth PL1 2PB, UK.
School of Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, UK.
Plant Physiol. 2022 Sep 28;190(2):1384-1399. doi: 10.1093/plphys/kiac324.
Diatoms are a group of microalgae that are important primary producers in a range of open ocean, freshwater, and intertidal environments. The latter can experience substantial long- and short-term variability in temperature, from seasonal variations to rapid temperature shifts caused by tidal immersion and emersion. As temperature is a major determinant in the distribution of diatom species, their temperature sensory and response mechanisms likely have important roles in their ecological success. We examined the mechanisms diatoms use to sense rapid changes in temperature, such as those experienced in the intertidal zone. We found that the diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana exhibit a transient cytosolic Ca2+ ([Ca2+]cyt) elevation in response to rapid cooling, similar to those observed in plant and animal cells. However, [Ca2+]cyt elevations were not observed in response to rapid warming. The kinetics and magnitude of cold-induced [Ca2+]cyt elevations corresponded with the rate of temperature decrease. We did not find a role for the [Ca2+]cyt elevations in enhancing cold tolerance but showed that cold shock induces a Ca2+-dependent K+ efflux and reduces mortality of P. tricornutum during a simultaneous hypo-osmotic shock. As intertidal diatom species may routinely encounter simultaneous cold and hypo-osmotic shocks during tidal cycles, we propose that cold-induced Ca2+ signaling interacts with osmotic signaling pathways to aid in the regulation of cell volume. Our findings provide insight into the nature of temperature perception in diatoms and highlight that cross-talk between signaling pathways may play an important role in their cellular responses to multiple simultaneous stressors.
硅藻是一类微藻，在开阔海域、淡水和潮间带等多种环境中都是重要的初级生产者。后两者的温度会经历长期和短期的显著变化，从季节性变化到潮汐浸泡和暴露引起的快速温度变化。由于温度是硅藻物种分布的主要决定因素，它们的温度感应和响应机制可能在其生态成功中发挥重要作用。我们研究了硅藻用于感应快速温度变化（如在潮间带经历的变化）的机制。我们发现，菱形藻（Phaeodactylum tricornutum）和拟菱形藻（Thalassiosira pseudonana）在快速冷却时表现出短暂的细胞质 Ca2+（[Ca2+]cyt）升高，类似于在植物和动物细胞中观察到的情况。然而，在快速升温时没有观察到 [Ca2+]cyt 升高。冷诱导的 [Ca2+]cyt 升高的动力学和幅度与温度下降的速度相对应。我们没有发现 [Ca2+]cyt 升高在增强耐寒性方面的作用，但表明冷休克诱导 Ca2+依赖性 K+外排，并降低菱形藻在同时发生的低渗冲击期间的死亡率。由于潮间带硅藻物种在潮汐周期中可能经常同时遇到寒冷和低渗冲击，我们提出冷诱导的 Ca2+信号与渗透信号途径相互作用，以帮助调节细胞体积。我们的发现深入了解了硅藻对温度的感知性质，并强调了信号通路之间的串扰可能在它们对多种同时应激源的细胞反应中发挥重要作用。
