Luo Qijun, Zhu Zhenggang, Zhu Zhujun, Yang Rui, Qian Feijian, Chen Haimin, Yan Xiaojun
Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Ningbo, Zhejiang, China.
School of Marine Science, Ningbo University, Ningbo, Zhejiang, China.
PLoS One. 2014 Apr 7;9(4):e94354. doi: 10.1371/journal.pone.0094354. eCollection 2014.
Pyropia has a unique heteromorphic life cycle with alternation stages between thallus and conchocelis, which lives at different water temperatures in different seasons. To better understand the different adaptation strategies for temperature stress, we tried to observe comparative biochemical changes of Pyropia haitanensis based on a short term heat shock model. The results showed that: (1) At normal temperature, free-living conchocelis contains significantly higher levels of H2O2, fatty acid-derived volatiles, the copy number of Phrboh and Phhsp70 genes,the activities of NADPH oxidase and floridoside than those in thallus. The released H2O2 and NADPH oxidase activity of conchocelis were more than 7 times higher than those of thallus. The copy number of Phrboh in conchocelis was 32 times that in thallus. (2) After experiencing heat shock at 35°C for 30 min, the H2O2 contents, the mRNA levels of Phrboh and Phhsp70, NADPH oxidase activity and the floridoside content in thallus were all significantly increased. The mRNA levels of Phrboh increased 5.78 times in 5 min, NADPH oxidase activity increased 8.45 times in 20 min. (3) Whereas, in conchocelis, the changes in fatty acids and their down-stream volatiles predominated, significantly increasing levels of saturated fatty acids and decreasing levels of polyunsaturated fatty acids occurred, and the 8-carbon volatiles were accumulated. However, the changes in H2O2 content and expression of oxidant-related genes and enzymatic activity were not obvious. Overall, these results indicate that conchocelis maintains a high level of active protective apparatus to endure its survival at high temperature, while thallus exhibit typical stress responses to heat shock. It is concluded that Pyropia haitanensis has evolved a delicate strategy for temperature adaptation for its heteromorphic life cycle.
紫菜具有独特的异形生活史，在叶状体和壳孢子体阶段交替，它们在不同季节生活在不同水温下。为了更好地了解对温度胁迫的不同适应策略，我们基于短期热休克模型尝试观察坛紫菜的比较生化变化。结果表明：（1）在常温下，自由生活的壳孢子体中过氧化氢、脂肪酸衍生挥发物、Phrboh和Phhsp70基因的拷贝数、NADPH氧化酶活性和 floridoside的含量显著高于叶状体。壳孢子体释放的过氧化氢和NADPH氧化酶活性比叶状体高7倍以上。壳孢子体中Phrboh的拷贝数是叶状体中的32倍。（2）在35°C热休克30分钟后，叶状体中的过氧化氢含量、Phrboh和Phhsp70的mRNA水平、NADPH氧化酶活性和floridoside含量均显著增加。Phrboh的mRNA水平在5分钟内增加了5.78倍，NADPH氧化酶活性在20分钟内增加了8.45倍。（3）然而，在壳孢子体中，脂肪酸及其下游挥发物的变化占主导，饱和脂肪酸水平显著增加，多不饱和脂肪酸水平降低，并且积累了8碳挥发物。但是，过氧化氢含量以及与氧化相关基因的表达和酶活性的变化并不明显。总体而言，这些结果表明壳孢子体维持高水平的活性保护机制以在高温下生存，而叶状体对热休克表现出典型的应激反应。得出的结论是，坛紫菜因其异形生活史进化出了一种精细的温度适应策略。
