Environmental selection pressures related to iron utilization are involved in the loss of the flavodoxin gene from the plant genome
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Date
2015-02-16
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Oxford University Press
Abstract
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Oxidative stress and iron limitation represent the grim side of life in an oxygen-rich atmosphere. The versatile electron transfer shuttle
ferredoxin,aniron-sulfurprotein,isparticularlysensitivetothesehardships,anditsdownregulationunderadverseconditionsseverely
compromises survival of phototrophs. Replacement of ferredoxin by a stress-resistant isofunctional carrier, flavin-containing flavodoxin, is a widespread strategy employed by photosynthetic microorganisms to overcome environmental adversities. The flavodoxin
gene was lostin the course ofplantevolution, but its reintroduction in transgenicplants confers increased tolerance to environmental
stress and iron starvation, raising the question as to whya genetic asset with obvious adaptive value was not kept by natural selection.
Phylogenetic analyses reveal that the evolutionary history of flavodoxin is intricate, with several horizontal gene transfer events
between distant organisms, including Eukarya, Bacteria, and Archaea. The flavodoxin gene is unevenly distributed in most algal
lineages, with flavodoxin-containing species being overrepresented in iron-limited regions and scarce or absent in iron-rich environments. Evaluation of cyanobacterial genomic and metagenomic data yielded essentially the same results, indicating that there was
little selection pressure to retain flavodoxin in iron-rich coastal/freshwater phototrophs. Our results show a highly dynamic evolution
pattern of flavodoxin tightly connected to the bioavailability of iron. Evidence presented here also indicates that the high concentration of iron in coastal and freshwater habitats may have facilitated the loss of flavodoxin in the freshwater ancestor of modern
plants during the transition of photosynthetic organisms from the open oceans to the firm land.
This article has been accepted for publication in Genome Biology and Evolution Published by Oxford University Press.
This article has been accepted for publication in Genome Biology and Evolution Published by Oxford University Press.
Keywords
Flavodoxin, Ferredoxins, Iron, Photosynthesis, Cyanobacteria, Algae