Li Chongping, Wong Joseph Tin Yum
Department of Ocean Science, The Hong Kong University of Science and Technology, Clearwater Bay, Kowloon, Hong Kong, China.
Division of Life Science, The Hong Kong University of Science and Technology, Clearwater Bay, Kowloon, Hong Kong, China.
Microorganisms. 2019 Jul 5;7(7):191. doi: 10.3390/microorganisms7070191.
Dinoflagellates are a general group of phytoplankton, ubiquitous in aquatic environments. Most dinoflagellates are non-obligate autotrophs, subjected to potential physical and chemical DNA-damaging agents, including UV irradiation, in the euphotic zone. Delay of cell cycles by irradiation, as part of DNA damage responses (DDRs), could potentially lead to growth inhibition, contributing to major errors in the estimation of primary productivity and interpretations of photo-inhibition. Their liquid crystalline chromosomes (LCCs) have large amount of abnormal bases, restricted placement of coding sequences at the chromosomes periphery, and tandem repeat-encoded genes. These chromosome characteristics, their large genome sizes, as well as the lack of architectural nucleosomes, likely contribute to possible differential responses to DNA damage agents. In this study, we sought potential dinoflagellate orthologues of eukaryotic DNA damage repair pathways, and the linking pathway with cell-cycle control in three dinoflagellate species. It appeared that major orthologues in photoreactivation, base excision repair, nucleotide excision repair, mismatch repair, double-strand break repair and homologous recombination repair are well represented in dinoflagellate genomes. Future studies should address possible differential DNA damage responses of dinoflagellates over other planktonic groups, especially in relation to possible shift of life-cycle transitions in responses to UV irradiation. This may have a potential role in the persistence of dinoflagellate red tides with the advent of climatic change.
甲藻是浮游植物的一个大类，在水生环境中普遍存在。大多数甲藻是非专性自养生物，在真光层会受到包括紫外线照射在内的潜在物理和化学DNA损伤剂的影响。作为DNA损伤反应（DDRs）的一部分，辐射导致细胞周期延迟可能会导致生长抑制，这在初级生产力估计和光抑制解释中会造成重大误差。它们的液晶染色体（LCCs）含有大量异常碱基，编码序列在染色体周边的位置受限，且有串联重复编码基因。这些染色体特征、它们较大的基因组大小以及缺乏结构核小体，可能导致对DNA损伤剂的反应存在差异。在本研究中，我们在三种甲藻物种中寻找真核生物DNA损伤修复途径的潜在甲藻直系同源物，以及与细胞周期控制相关的连接途径。看来，光复活、碱基切除修复、核苷酸切除修复、错配修复、双链断裂修复和同源重组修复中的主要直系同源物在甲藻基因组中都有很好的体现。未来的研究应该探讨甲藻与其他浮游生物群体相比可能存在的不同DNA损伤反应，特别是与紫外线照射下生命周期转变的可能变化有关。随着气候变化的出现，这可能在甲藻赤潮的持续存在中发挥潜在作用。
