Overexpression of the ABC transporter gene TsABCG11 increases cuticle lipids and abiotic stress tolerance in Arabidopsis

The cuticle, composed primarily of wax and cutin, covers most plant aerial surfaces and plays a vital role in interactions between plants and their environment. Some ATP-binding cassette G subfamily (ABCG) members are involved in cuticular lipid molecule exportation to outside in the plant surface. Thellungiella salsugineum, a relative of Arabidopsis thaliana with a heavy cuticle, has extreme stress tolerance. TsABCG11, an ABCG transporter was cloned (GenBank accession number JQ389853), and its structure was studied. qRT-PCR showed that TsABCG11 expression varied in different organs of T. salsugineum and was upregulated under ABA, NaCl, drought and cold conditions. The rosette leaves from 4-week-old TsABCG11 overexpressed (OE) Arabidopsis plants displayed lower rates of water loss and decreased chlorophyll-extracted rates compared to wild-type plants. TsABCG11-OE plants also exhibited significantly increased total cuticular wax and cutin monomer amounts, mainly due to prominent changes in the C-29, C-31, and C-33 alkanes in the wax and C18:2 dioic in cutin monomers, respectively. TsABCG11-OE seedlings exhibit lower root growth inhibition under 100mM of NaCl or 1 mu M of ABA than the wild type. Four-week-old TsABCG11-OE plants exhibited higher photosynthetic rates and water-use efficiency under cold stress (4 degrees C) than control plants. These results indicate that TsABCG11 plays an important role in cuticle lipid exportation and is involved in abiotic stresses, probably having a close relationship with extreme stress tolerance in T. salsugineum.