Stress‐inducible flavodoxin from photosynthetic microorganisms. The mystery of flavodoxin loss from the plant genome

Abstract

SummaryFlavodoxins (Flds) are mobile electron carriers containing flavin mononucleotide as the prosthetic group. They are isofunctional with the ubiquitous electron shuttle ferredoxin (Fd), mediating essentially the same redox processes among a promiscuous lot of donors and acceptors. While Fds are distributed throughout all kingdoms from prokaryotes to animals, Flds are only found in some bacteria and oceanic algae, in which they are induced to replace Fd functions under conditions of iron starvation and environmental stress that cause Fd decline. They thus play a key adaptive role in photosynthetic microorganisms, allowing survival and reproduction under adverse situations. The Fld gene disappeared from the plant genome somewhere between the green algal ancestor and the first terrestrial plants, and the advantages of this adaptive resource were irreversibly lost. However, reintroduction of a cyanobacterial Fld gene in the chloroplasts of transgenic tobacco resulted in remarkably enhanced tolerance to iron starvation and abiotic stress, indicating that the compensatory functions of Fld were still valuable in higher plants. A hypothesis is formulated to explain why Fld, in spite of its proven advantage, was lost from the plant genetic pool. The contention is based on two tenets: (i) iron availability was the major imperative for Fld conservation and adaptive value, and (ii) photosynthetic eukaryotes followed a succession of ecological adaptations, from the open oceans to coastal regions, and from there to the firm land, facing very different scenarios with respect to iron abundance and accessibility. IUBMB Life, 59: 355-360, 2007

Identification of Putative Stage-Specific Grapevine Berry Biomarkers and Omics Data Integration into Networks

“…Two isoforms of pectate lyase (235 and 258) and a gene encoding a mannan-endo-1,4-b-mannosidase (TC68167) are associated with cell wall metabolism during berry growth (Nunan et al, 2001;Glissant et al, 2008). The network also includes a Rubisco large subunit-binding protein subunit a (212), which is involved in Rubisco oligomer assembly (Viitanen et al, 1995), flavoprotein WrbA (1380), which is related to flavodoxins (Zurbriggen et al, 2007), and a transcript encoding plastid carbonic anhydrase (TC55155; Majeau and Coleman, 1991), all of which support photosynthesis during berry formation. Transcripts for the 50S ribosomal protein L19 (TC52388) and a boron transporter (TC68987) are also present, the latter likely involved in the transport of HCO 3 2 , which is a potential supplier of CO 2 to Rubisco.…”

Spatial variability in iron nutritional status of large diatoms in the Sea of Okhotsk with special reference to the Amur River discharge

“…The small (6-15 kDa) nonheme protein Fd accepts electrons from PSI and transfers them to Fd NADP + reductase (FNR), acting in both cyclic and non-cyclic electron transport systems . By comparison, Fld, a flavoprotein ranging from 16-20 kDa (Zurbriggen et al, 2007), has an oxidation-reduction potential resembling that of Fd (ca. −400 mV; Medina and Gómez-Moreno, 2004), while the energetic cost of Fld synthesis could be slightly higher than that of Fd due to the larger size.…”

“…Fe deficiency in the large diatoms was assessed by determining the ferredoxin (Fd) index, which is defined as the proportion of Fd to the sum of Fd plus flavodoxin (Fld) accumulations (Doucette et al, 1996). Under Fe deficient conditions, the Fe-S (iron-sulfur) protein Fd, which is located in the acceptor side of photosystem I (PSI), can be replaced by a functionally equivalent non-Fe-containing Fld in most cyanobacteria and some eukaryotic algae including diatoms (Zurbriggen et al, 2007). The small (6-15 kDa) nonheme protein Fd accepts electrons from PSI and transfers them to Fd NADP + reductase (FNR), acting in both cyclic and non-cyclic electron transport systems .…”

Iron and Prochlorococcus

“…The first mechanism of dealing with low iron availability is through a concerted reduction of the cellular iron requirement, or iron quota. This intracellular adjustment is exemplified by the replacement of the iron-containing electron transfer protein ferredoxin with the iron-free protein flavodoxin in prokaryotic and eukaryotic photosynthetic microorganisms (Meimberg et al, 1999;Sancho, 2006;Zurbriggen et al, 2007).…”