Identification Of A Putative ATP-Binding Cassette Transporter Gene OsPDR20 For Accumulation And Detoxification Of Cadmium And Zinc In Rice

With the rapid industrialization and urbanization,a growing emission of toxic heavy metals such as cadmium（Cd）and zinc（Zn）has been contaminated agricultural soils.Accumulation of heavy metals in crops not only affects grain yield and quality,but also causes human diseases.Therefore,this paper takes China’s most important cereal crop as research material studies the absorption,accumulation,and detoxification effects of heavy metals in rice through biochemical,molecular physiology,genetics methods.ATP-Binding Cassette（ABC）transporters are one of the largest known protein superfamilies.ABC transporters have ATP binding domains and transmembrane structures.energy is obtained through the binding and hydrolysis of ATP to complete the translocation of substances.There are 8 subfamilies in the rice ABC family,of which ABCG is the largest subfamily,which can be further divided into white-brown complex（WBC）and pleiotropic drug resistance（PDR）groups.This paper studies the unknown function of OsPDR20,one of the PDR members of the ABCG family.First,the bioinformatics analysis of the OsPDR20 was performed.The sequence of OsPDR20 is 1272 bp encodes 423 aa,with seven exons and six intron.The OsPDR20 has two domains including ATP-binding domain and ABC2 membrane domain,with seven transmembrane structures.This research cloned the full-length CDS sequence of OsPDR20,detect its expression pattern throughout the rice growth cycle,we found that OsPDR20 was mainly expressed in roots,leaf sheaths and leaves.It was substantially heavily induced by heavy metals Cd and Zn.The rice protoplasts subcellular localization studies revealed that OsPDR20 was localized to the cytoplasmic membrane.Then we transferred OsPDR20 into yeast（Saccharomyces cerevisiae）and found that expression of OsPDR20 could effectively reduce the concentration of Cd and Zn in cells and the toxicity to yeast cells.To study the function of OsPDR20 in rice,we ordered a OsPDR20 homozygous mutant lines.At the same time,OsPDR20 overexpression and RNA interference vectors were constructed,and homozygous rice transgenic lines were obtained through Agrobacterium infection.Under excess Cd and Zn stress,OsPDR20 mutants and RNAi lines had poor growth phenotypes relative to the wild type,showing shorten plant height and root length,and accumulation of more metal ions in the plants.OsPDR20 overexpression lines treated with excessive Cd and Zn showed better growth of rice plants relative to the wild type,Furthermore the content of metal ions in overexpression lines was less than that of wild type.OsPDR20 overexpression alleviating the toxicity of Cd and Zn to plants.In summary,OsPDR20 is involved in the transport of heavy metals Cd and Zn in yeast and rice.It played an important role in alleviating the toxicity of the heavy metals to rice.