open access

https://hdl.handle.net/2115/90680

Heterologous complementation systems verify the mosaic distribution of three distinct protoporphyrinogen IX oxidase in the cyanobacterial phylum

英語

Tetrapyrrole

2022-11-10

Springer

Journal of plant research

136

107-115

The pathways for synthesizing tetrapyrroles, including heme and chlorophyll, are well-conserved among organisms, despite the divergence of several enzymes in these pathways. Protoporphyrinogen IX oxidase (PPOX), which catalyzes the last common step of the heme and chlorophyll biosynthesis pathways, is encoded by three phylogenetically-unrelated genes, hemY, hemG and hemJ. All three types of homologues are present in the cyanobacterial phylum, showing a mosaic phylogenetic distribution. Moreover, a few cyanobacteria appear to contain two types of PPOX homologues. Among the three types of cyanobacterial PPOX homologues, only a hemJ homologue has been experimentally verified for its functionality. An objective of this study is to provide experimental evidence for the functionality of the cyanobacterial PPOX homologues by using two heterologous complementation systems. First, we introduced hemY and hemJ homologues from Gloeobacter violaceus PCC7421, hemY homologue from Trichodesmium erythraeum, and hemG homologue from Prochlorococcus marinus MIT9515 into a Delta hemG strain of E. coli. hemY homologues from G. violaceus and T. erythraeum, and the hemG homologue of P. marinus complimented the E. coli strain. Subsequently, we attempted to replace the endogenous hemJ gene of the cyanobacterium Synechocystis sp. PCC6803 with the four PPOX homologues mentioned above. Except for hemG from P. marinus, the other PPOX homologues substituted the function of hemJ in Synechocystis. These results show that all four homologues encode functional PPOX. The transformation of Synechocystis with G. violaceus hemY homologue rendered the cells sensitive to an inhibitor of the HemY-type PPOX, acifluorfen, indicating that the hemY homologue is sensitive to this inhibitor, while the wild-type G. violaceus was tolerant to it, most likely due to the presence of HemJ protein. These results provide an additional level of evidence that G. violaceus contains two types of functional PPOX.

学術雑誌論文

Accepted Manuscript

This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s10265-022-01423-7

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