Balancing Damage via Non-Photochemical Quenching, Phenolic Compounds and Photorespiration in Ulva prolifera Induced by Low-Dose and Short-Term UV-B Radiation.

Yi Zhong,Ying Wang,Chengzong Hou,Chen Guan,Xinyu Zhao,Xuexi Tang,Jinhui Xu,Tongfei Qu

doi:10.3390/ijms23052693

Abstract

The Yellow Sea green tide (YSGT) is the world’s largest transregional macroalgal blooms, and the causative species Ulva prolifera (U. prolifera) suffers from ultraviolet-b radiation (UVBR) during the floating migration process. Previous study confirmed that U. prolifera displayed a wide variety of physiological responses characterized as acclimation to UVBR, while the response mechanisms against low-dose and short-term radiation (LDSTR) are not clear. A study with photosynthetically active radiation (PAR) and UVBR was designed: normal light (NL: 72 μmol photons m−2 s−1), NL+0.3 (UVBR: 0.3 W·m−2), and NL+1.6 (UVBR: 1.6 W·m−2). The results showed that high-dose UVBR inhibited photosynthesis in thalli, especially under long-term exposure, while a variety of physiological responses were observed under LDSTR. The inhibition of photosynthesis appeared to be ameliorated by the algae under LDSTR. Further analysis showed that U. prolifera achieved balancing damage by means of non-photochemical quenching (NPQ), accumulation of phenolic compounds coupled with the ASA-GSH cycle involved in the antioxidant process and enhanced photorespiratory metabolism under LDSTR. This study provides new insights into the balancing damage mechanisms of U. prolifera under LDSTR, enabling the thalli to adapt to the light conditions during the long duration and distance involved in floating migration.

Highlights

Intertidal macroalgae grow in the intertidal zone and usually undergo both submerged and exposed dry-out environmental changes with the tides
Compared with the content under normal light (NL), we observed that the relative content of phenolic compounds was significantly increased under other treatments and that the content was higher at 2 d than at 1 d (Figure 5A)
We found that GLYK activity and 3-PG content decreased and that Rubisco activity increased, indicating that U. prolifera could enhance the accumulation of starch grains under high doses of ultraviolet-b radiation (UVBR)

Summary

Introduction

Intertidal macroalgae grow in the intertidal zone and usually undergo both submerged and exposed dry-out environmental changes with the tides. Shallow-growing or dried-out macroalgae are exposed to strong solar radiation that exceeds the energy requirements provided by their photosynthesis for assimilation [2]. It is well known that solar radiation reaching the Earth’s surface contains ultraviolet-b (UV-B). The thinning of the ozone layer has led to more. UVBR accounts for only a small proportion of the total solar radiation, it has significant ecological and biological effects [3,4]

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Discussion

Conclusion