Özet:
Boron is a micronutrient in plants and animals, but its specific roles in cellular processes are not known. To
understand boron transport and functions, we screened a yeast genomic DNA library for genes that confer
resistance to the element in Saccharomyces cerevisiae. Thirty boron-resistant transformants were isolated, and
they all contained the ATR1 (YML116w) gene. Atr1 is a multidrug resistance transport protein belonging to the
major facilitator superfamily. C-terminal green fluorescent protein-tagged Atr1 localized to the cell membrane
and vacuole, and ATR1 gene expression was upregulated by boron and several stress conditions. We found that
atr1 mutants were highly sensitive to boron treatment, whereas cells overexpressing ATR1 were boron
resistant. In addition, atr1 cells accumulated boron, whereas ATR1-overexpressing cells had low intracellular
levels of the element. Furthermore, atr1 cells showed stronger boron-dependent phenotypes than mutants
deficient in genes previously reported to be implicated in boron metabolism. ATR1 is widely distributed in
bacteria, archaea, and lower eukaryotes. Our data suggest that Atr1 functions as a boron efflux pump and is
required for boron tolerance.
