Comparative molecular population genetics of phycoerythrin locus in <Emphasis Type="Italic">Prochlorococcus</Emphasis> |
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Authors: | Fangqing Zhao Song Qin |
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Institution: | (1) Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao, 266071, China;(2) Graduate School, Chinese Academy of Sciences, Qingdao, China |
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Abstract: | As the only remainder type of phycobiliproteins in Prochlorococcus, the actual role of phycoerythrin still remains unknown. Previous studies revealed that two different forms of phycoerythrin
gene were found in two ecotypes of Prochlorococcus that are specifically adapted to either high light (HL) or low light (LL) conditions. Here we analyze patterns of phycoerythrin
nucleotide variation in the HL- and LL-Prochlorococcus populations. Our analyses reveal a significantly greater number of non-synonymous fixed substitutions in peB and peA than expected based on interspecific comparisons. This pattern of excess non-synonymous fixed substitutions is not seen in
other five phycoerythrin-related genes (peZ/V/Y/T/S). Several neutrality statistical tests indicate an excess of rare frequency polymorphisms in the LL-Prochlorococcus data, but an excess of intermediate frequency polymorphisms in the HL-Prochlorococcus data. Distributions of the positively selected sites identified using the likelihood ratio test, when mapped onto the phycoerythrin
tertiary structure, reveal that HL- and LL-phycoerythrin should be under different selective patterns. These findings may
provide insights into the likely role of selection at the phycoerythrin locus and motivate further research to unveil the
function of phycoerythrin in Prochlorococcus. |
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Keywords: | Neutrality statistical test Phycoerythrin Population genetics Positive selection Prochlorococcus |
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