ABCG transporter proteins with beneficial activity on plants.

Among the several subfamilies of ABC transporters the ABC-G subfamily is very significant. In the model plant Arabidopsis thaliana itself, ABCG subfamily houses highest number of transporters with mostly half-size transporters (called WBC) and fewer full-size transporters (called PDR). During drought stress the stress hormone abscisic acid (ABA) is exported from the root xylem and imported by the leaf stomatal cells by ABCG transporter proteins to reduce the transpiration of water from leaves. Moreover, the ABCG transporters play a chief role in export of prime biotic stress induced hormones like jasmonic acid and salicylic acid among other secondary metabolites. In this way they protect the plant as the first line of defense against pathogenic damages. The ABCG transporters help the plant in becoming kanamycin resistant which help in plant growth. ABCG transporters of Nicotiana plumbaginifolia provide resistance to pathogens like Pseudomonas syringae. Furthermore several ABCG transporters of A. thaliana are efficient in transporting cuticular lipids like cutin to help development of cuticle. Pollen exine wall formation is also aided by one ABCG transporter itself. Some important ABCG transporters like ABCG36 and ABCG40 have been suggested to contribute hugely towards heavy metal resistance and cellular detoxification in Arabidopsis thaliana.