A novel ATP‐binding cassette transporter is responsible for resistance to viologen herbicides in the cyanobacterium Synechocystis sp. PCC 6803

Abstract

The charged quaternary ammonium compounds – methyl, ethyl and benzyl viologens – generate reactive oxygen species in photosynthetic cells. Three independent methyl viologen‐resistant spontaneous mutants of Synechocystis sp. PCC 6803 were identified, in which the conserved R115 residue of the Slr1174 protein was replaced with G115, L115 and C115. The Slr1174 protein of the DUF990 family is related to the permease subunit of an ABC‐2‐type transporter and its R115 mutation was found to be solely responsible for the observed methyl viologen resistance. Bioinformatic analysis showed that in various bacterial genomes, two genes encoding another permease subunit and the ATPase component of an ATP‐binding cassette transporter form putative operons with slr1174 orthologs, suggesting that the protein products of these genes may form functional transporters. The corresponding genes in Synechocystis sp. PCC 6803, i.e. slr0610 for the permease and slr1901 for the ATPase, did not form such an operon. However, insertional inactivation of any slr1174, slr0610 or slr1901 genes in both the wild‐type and the R115‐resistant mutant resulted in increased sensitivity to methyl, ethyl and benzyl viologens; moreover, single‐ and double‐insertion mutants did not differ in their viologen sensitivity. Our data suggest that Slr1901, Slr1174 and Slr0610 form a heteromeric ATP‐binding cassette‐type viologen exporter, in which each component is critical for viologen extrusion. Because the greatest increase in mutant sensitivity was observed in the case of ethyl viologen, the three proteins have been named EvrA (Slr1901), EvrB (Slr1174) and EvrC (Slr0610). This is the first report of a function for a DUF990 family protein.

In Vivo 31P-Nuclear Magnetic Resonance Studies of Glyphosate Uptake, Vacuolar Sequestration, and Tonoplast Pump Activity in Glyphosate-Resistant Horseweed

“…Furthermore, glyphosate entry into the cell can be markedly inhibited by vanadate pretreatment. These characteristics are similar to those of ATP-binding cassette transporters in plants (Hetherington et al, 1998;Rea, 2007;Verrier et al, 2008;Prosecka et al, 2009;Conte and Lloyd, 2011) and mammalian cells (van de Ven et al, 2009;Ernst et al, 2010).…”

Integrated Transcriptomic and Proteomic Analysis of the Bile Stress Response in a Centenarian-originated Probiotic Bifidobacterium longum BBMN68

“…In addition, the transcription level of BN_1434-1433 encoding an ABC-2 type transporter was respectively 3.59-and 4.73-fold up-regulated under bile stress conditions. Among ABC-2 type transporters, Drr and Evr have been reported to pump toxic compounds, such as daunorubicin and doxorubicin in Streptomyces lucretius (49) and viologen in Synechocystis (50). These results suggested that this transporter may possibly perform similar function of bile exclusion in BBMN68 in response to bile stress.…”

Evolution in Action: Plants Resistant to Herbicides

“…Huang, and S. Powles, unpublished data). In bacteria, several multidrug transporter genes have been isolated that confer paraquat resistance by paraquat extrusion or sequestration (e.g., 147,186). Recently, two differentially expressed EST sequences were identified in paraquat-resistant C. canadensis.…”