Early genome erosion and internal phage-symbiont-host interaction in the endosymbionts of a cold-seep tubeworm
Zhao-Ming Gao,
Ting Xu,
Hua-Guan Chen,
Rui Lu,
Jun Tao,
Hong-Bin Wang,
Jian-Wen Qiu,
Yong Wang
Affiliations
Zhao-Ming Gao
Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China; HKUST-CAS Sanya Joint Laboratory of Marine Science Research, Chinese Academy of Sciences, Sanya 572000, China
Ting Xu
Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China
Hua-Guan Chen
Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China; University of Chinese Academy of Sciences, Beijing 101408, China
Rui Lu
Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China; University of Chinese Academy of Sciences, Beijing 101408, China
Jun Tao
MLR Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 511458, China
Hong-Bin Wang
MLR Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 511458, China
Jian-Wen Qiu
Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China; Department of Biology, Hong Kong Baptist University, Hong Kong, China; Corresponding author
Yong Wang
Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China; HKUST-CAS Sanya Joint Laboratory of Marine Science Research, Chinese Academy of Sciences, Sanya 572000, China; Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518000, China; Corresponding author
Summary: Endosymbiosis with chemosynthetic Gammaproteobacteria is widely recognized as an adaptive mechanism of siboglinid tubeworms, yet evolution of these endosymbionts and their driving forces remain elusive. Here, we report a finished endosymbiont genome (HMS1) of the cold-seep tubeworm Sclerolinum annulatum. The HMS1 genome is small in size, with abundant prophages and transposable elements but lacking gene sets coding for denitrification, hydrogen oxidization, oxidative phosphorylation, vitamin biosynthesis, cell pH and/or sodium homeostasis, environmental sensing, and motility, indicative of early genome erosion and adaptive evolution toward obligate endosymbiosis. Unexpectedly, a prophage embedded in the HMS1 genome undergoes lytic cycle. Highly expressed ROS scavenger and LexA repressor genes indicate that the tubeworm host likely activates the lysogenic phage into lytic cycle through the SOS response to regulate endosymbiont population and harvest nutrients. Our findings indicate progressive evolution of Sclerolinum endosymbionts toward obligate endosymbiosis and expand the knowledge about phage-symbiont-host interaction in deep-sea tubeworms.
