Tric proteins and TOM complex subunits are involved in the import of short DNA fragments into Arabidopsis mitochondria.

A large set of tRNAs is imported into the plant mitochondria from the cytosol. Besides tRNA import, the mitochondria are capable of uptaking DNA from the cytosol. These two processes may partially overlap, but little is known about which membrane proteins act as carriers for both DNA and RNA. In our work, we studied the role of tRNA carriers in the outer mitochondrial membrane in DNA transfer into the Arabidopsis mitochondria. The outer membrane translocase receptor subunit Tom20-2 and tRNA import-engaged Tric1/Tric2 proteins are involved in the import of short (265 bp), but not long (2.7 kb), DNA fragments. The presence of one of the Tric subunits is sufficient for the normal functioning of the DNA transport channel formed by these proteins. Based on treatment of mitochondria isolated from tric1/tric2 knockout line with antibodies, we suggest that Tric1/2 plays a central role in the import of not only tRNA but also short-length DNA fragments, sharing channel with VDAC1 and Tom40. Thus, our results suggest that Tric1/2 proteins and TOM complex subunits take part in both tRNA and DNA translocation, revealing a new layer of multifunctionality of outer membrane carrier proteins.