title: Indian mustard aquaporin improves drought and heavy-metal resistance in tobacco.
abstract: An aquaporin cDNA BjPIP1 isolated from heavy-metal accumulator Indian mustard (Brassica juncea L.) encodes a 286-residue protein. The deduced amino acid sequence of BjPIP1 with six putative transmembrane domains showed highest identity (85-99%) to PIP1 subfamily members. Semi-quantitative RT-PCR analysis revealed that BjPIP1 transcripts were more abundantly expressed in roots compared to aerial parts of Indian mustard. However, the expression of BjPIP1 in leaves was up-regulated by drought, salt, low temperature, and heavy metal stress, suggesting that BjPIP1 was involved in resistance to abiotic stresses. BjPIP1 under the control of 35S promoter was introduced into tobacco mediated with Agrobacterium tumefaciens, the transgenic tobacco exhibited a lower water loss rate, a decreased transpiration rate, and stomatal conductance compared to the wild-type plants under osmotic stress, indicating that BjPIP1 might enhance plant drought resistance by decreasing transpiration via reducing stomatal conductance. Furthermore, overexpression of BjPIP1 in tobacco enhanced Cd resistance of root growth, and lowered transpiration rate and stomatal conductance upon Cd exposure, suggesting that BjPIP1 might increase heavy-metal resistance by maintaining reasonable water status in tobacco. Moreover, the BjPIP1-overexpressing plants showed higher activities of antioxidative enzymes, and lower level of electrolyte leakage and malondialdehyde content under Cd stress, indicating BjPIP1 might enhance the antioxidative activity and membrane integrity in transgenic plants. Taken together, these results suggested that BjPIP1 might improve plant heavy-metal resistance through alleviating water deficit and oxidative damage induced by metal ions.
authors.affiliation: Department of Bioengineering, School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), 11 Xueyuan Road, Beijing 100083, China. zhangyuxiu@cumtb.edu.cn
authors.forename: Yuxiu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zi
authors.initials: Z
authors.lastname: Wang
authors.forename: Tuanyao
authors.initials: T
authors.lastname: Chai
authors.forename: Zhensong
authors.initials: Z
authors.lastname: Wen
authors.forename: Hongmei
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000975:Antioxidants / Q000378:metabolism; D020346:Aquaporins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003890:Desiccation; D055864:Droughts; D004573:Electrolytes; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008315:Malondialdehyde / Q000378:metabolism; D019216:Metals, Heavy / Q000633:toxicity*; D008969:Molecular Sequence Data; D009149:Mustard Plant / Q000235:genetics; D010788:Photosynthesis / Q000187:drug effects; D010802:Phylogeny; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D054046:Plant Stomata / Q000187:drug effects; D018526:Plant Transpiration / Q000187:drug effects; D030821:Plants, Genetically Modified; D013312:Stress, Physiological / Q000187:drug effects; D014026:Nicotiana / Q000187:drug effects* / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000975:Antioxidants; D020346:Aquaporins; D004573:Electrolytes; D019216:Metals, Heavy; D008315:Malondialdehyde