Department of Bioscience, Tokyo University of Agriculture, Tokyo, 156-8502, Japan.
Department of Bioscience, Tokyo University of Agriculture, Tokyo, 156-8502, Japan.
Biochem Biophys Res Commun. 2021 Jan 1;534:747-751. doi: 10.1016/j.bbrc.2020.11.006. Epub 2020 Nov 14.
Plants are often exposed not only to short-term (S-) heat stress but also to diurnal long-term (L-) heat stress over several consecutive days; nevertheless, most previous studies of heat tolerance have used S-heat stress, such as 42 °C for 30-60 min, for evaluation. Yet the mechanisms underlying L-heat tolerance remain poorly understood. Here we found that hydrogen peroxide (HO) in Arabidopsis thaliana plants increased time-dependently under L-heat stress (37 °C, 5 days) but not under S-heat stress (42 °C, 40 min). To reveal the contribution of reactive oxygen species (ROS) scavenging to heat tolerance, we evaluated the heat tolerance of ROS mutants. Only cat2 mutants, in which catalase (CAT) activity is defective, were hypersensitive to L-heat stress, but they were S-heat tolerant. We further revealed that (1) CAT2 was induced by L-heat stress but not by S-heat stress; (2) HO accumulated highly in cat2 under L-heat stress, but not in cat1, cat3, or wild type; and (3) CAT activity was significantly reduced in cat2 under both normal and L-heat conditions. These results suggest that ROS scavenging is responsible for L-heat tolerance, and CAT2 plays a crucial role. On the other hand, since overexpression of CAT2 in wild-type plants did not enhance L-heat tolerance, CAT2 activity is necessary but insufficient for increasing L-heat tolerance.
植物不仅经常会遭受短期（S-）热应激，还会连续数天遭受昼夜长期（L-）热应激；然而，大多数先前关于耐热性的研究都使用 S-热应激，例如 42°C 持续 30-60 分钟，来进行评估。然而，L-耐热性的机制仍知之甚少。在这里，我们发现拟南芥中的过氧化氢（HO）在 L-热应激（37°C，5 天）下会随时间增加，但在 S-热应激（42°C，40 分钟）下不会。为了揭示活性氧（ROS）清除对耐热性的贡献，我们评估了 ROS 突变体的耐热性。只有 CAT2 突变体（CAT 活性有缺陷）对 L-热应激敏感，而对 S-热应激耐受。我们进一步揭示：（1）L-热应激诱导 CAT2，但不诱导 S-热应激；（2）CAT2 在 L-热应激下 HO 大量积累，但在 CAT1、CAT3 或野生型中没有；（3）CAT2 在正常和 L-热条件下的 CAT 活性都显著降低。这些结果表明，ROS 清除负责 L-耐热性，而 CAT2 起着关键作用。另一方面，由于 CAT2 在野生型植物中的过表达并没有增强 L-耐热性，因此 CAT2 活性对于增加 L-耐热性是必要的，但不充分。
