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Plant Ferritins: A Conserved Protein Family with Significant Molecular Evolutionary Residues

Rong Wang, Qi Qi, Lihui Wang, Yaxuan Li, Yueming Yan, Yingkao Hu

Abstract


The ferritin complex protein plays a vital role in the iron homeostasis of all organisms. Plant ferritin, especially from legume seeds, represents a novel alternative source of dietary iron for humans and animals. However, little is known about the ferritin molecular evolution in plant genomes. Comparative genomic analysis was performed to explore the phylogenetic relationships, functional divergence, selection pressure, and coevolution of ferritins. Ninety-eight ferritin genes were identified from five main lineages containing 33 species. These genes were classified into three distinct groups (I–III), supported by high posterior probability and similarities in their structural motifs. Seven critical amino acid sites were detected that may have contributed to functional divergence between the three distinct groups. Although, a site-specific model predicted five positive sites, implying a role for positive selection in ferritin evolution, a branch-site model failed to support that hypothesis. None of the detected was associated with well-known ferroxidase center sites, C-terminal extension, extension peptide (EP) and transit peptide (TP); the sole exception was a functional divergence site (60I) in the EP region. Moreover, a comparison of protein sequences uncovered only one group of coevolved amino acid sites. These data suggest that the evolutionary history of plant ferritin genes involved several major residues. Finally, no plant genome contained over six ferritin genes except the soybean, with nine genes preserved through whole-genome duplication. These results provide novel insights into the genetic divergence patterns and evolutionary rates of plant ferritins.


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