Fe-responsive accumulation of redox proteins ferredoxin and flavodoxin in a marine cryptomonad

Abstract

Fe deficiency has been documented in diverse marine environments ranging from pelagic high-nutrient, low chlorophyll (HNLC) regions to coastal systems. Detection of specific Fe-responsive proteins in phytoplankton has provided a sensitive approach to assessing Fe deficiency in natural waters. Here, we report on the development and applicability of taxon-specific polyclonal antisera to monitor the accumulation of two such Fe-responsive proteins, flavodoxin and ferredoxin (Fd) in cryptomonad algae. Reactivity of these immunoreagents was limited primarily to cryptomonads. Anti-Fd cross-reacted with a broad spectrum of both marine and freshwater cryptophytes whereas anti-flavodoxin recognized only flavodoxin from Rhodomonas lens. Assessment of Fd and flavodoxin accumulation in R. lens grown under various levels of Fe demonstrated an apparent uncoupling of flavodoxin expression from physiological Fe deficiency in this species. It appears that flavodoxin accumulates in response to external Fe availability as supported by results of a chelator addition experiment which demonstrated rapid accumulation of flavodoxin in Fe-replete cells of R. lens without concomitant physiological deficit following addition of the fungal siderophore desferrioxamine B.

Elemental Economy

“…The Fe-regulated substitution of ferredoxin with flavodoxin as a major electron carrier has been noted in numerous organisms including a chlorophyte alga, several cyanobacterial species, cryptomonads, and diatoms (e.g. Zumft and Spiller, 1971, Hutber et al, 1977, Sandmann and Malkin, 1983, Ragsdale and Ljungdahl, 1984, McKay et al, 1997, Li et al, 2004). The reciprocal pattern of expression is consistent with an Fe-sparing mechanism, since the substitution will decrease the Fe quota of the cell.…”

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

“…Fd/(Fd + Fld)) proposed by Doucette et al (1996). In Fe-sufficient algae, the Fd index approaches 1 (e.g., Li et al, 2004;Strzepek and Harrison, 2004), indicating that only Fd has accumulated in the cells.…”

Rhinomonas nottbeckin. sp. (Cryptomonadales) and Molecular Phylogeny of the Family Pyrenomonadaceae

“…; Li et al. ). The family is cosmopolitan and commonly encountered in marine, brackish, and fresh water (Cerino and Zingone ; Hill and Wetherbee ; Kugrens et al.…”

“…Cultures of Pyrenomonadaceae species are widely used in biological experiments (e.g. Buttino et al 2009;Debelius et al 2009;Li et al 2004). The family is cosmopolitan and commonly encountered in marine, brackish, and fresh water (Cerino and Zingone 2006;Hill and Wetherbee 1989;Kugrens et al 1999).…”