title: Identification of quantitative trait loci and candidate genes for cadmium tolerance in Populus.
abstract: Understanding genetic variation for the response of Populus to heavy metals like cadmium (Cd) is an important step in elucidating the underlying mechanisms of tolerance. In this study, a pseudo-backcross pedigree of Populus trichocarpa Torr. & Gray and Populus deltoides Bart. was characterized for growth and performance traits after Cd exposure. A total of 16 quantitative trait loci (QTL) at logarithm of odds (LOD) ratio ≥ 2.5 were detected for total dry weight, its components and root volume. Major QTL for Cd responses were mapped to two different linkage groups and the relative allelic effects were in opposing directions on the two chromosomes, suggesting differential mechanisms at these two loci. The phenotypic variance explained by Cd QTL ranged from 5.9 to 11.6% and averaged 8.2% across all QTL. A whole-genome microarray study led to the identification of nine Cd-responsive genes from these QTL. Promising candidates for Cd tolerance include an NHL repeat membrane-spanning protein, a metal transporter and a putative transcription factor. Additional candidates in the QTL intervals include a putative homolog of a glutamate cysteine ligase, and a glutathione-S-transferase. Functional characterization of these candidate genes should enhance our understanding of Cd metabolism and transport and phytoremediation capabilities of Populus.
authors.affiliation: Department of Biology, West Virginia University, 53 Campus Drive, Morgantown, WV 26506-6057, USA.
authors.forename: Brahma Reddy
authors.initials: BR
authors.lastname: Induri
authors.forename: Danielle R
authors.initials: DR
authors.lastname: Ellis
authors.forename: Gancho T
authors.initials: GT
authors.lastname: Slavov
authors.forename: Tongming
authors.initials: T
authors.lastname: Yin
authors.forename: Xinye
authors.initials: X
authors.lastname: Zhang
authors.forename: Wellington
authors.initials: W
authors.lastname: Muchero
authors.forename: Gerald A
authors.initials: GA
authors.lastname: Tuskan
authors.forename: Stephen P
authors.initials: SP
authors.lastname: DiFazio
mesh_terms: D002104:Cadmium / Q000378:metabolism*; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D008040:Genetic Linkage; D016017:Odds Ratio; D032107:Populus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D040641:Quantitative Trait Loci
chemical_list: D002104:Cadmium