title: Comparative mapping combined with homology-based cloning of the rice genome reveals candidate genes for grain zinc and iron concentration in maize.
abstract: BACKGROUND
  Grain zinc and iron concentration is a complex trait that is controlled by quantitative trait loci (QTL) and is important for maintaining body health. Despite the substantial effort that has been put into identifying QTL for grain zinc and iron concentration, the integration of independent QTL is useful for understanding the genetic foundation of traits. The number of QTL for grain zinc and iron concentration is relatively low in a single species. Therefore, combined analysis of different genomes may help overcome this challenge.
  
  
  RESULTS
  As a continuation of our work on maize, meta-analysis of QTL for grain zinc and iron concentration in rice was performed to identify meta-QTL (MQTL). Based on MQTL in rice and maize, comparative mapping combined with homology-based cloning was performed to identify candidate genes for grain zinc and iron concentration in maize. In total, 22 MQTL in rice, 4 syntenic MQTL-related regions, and 3 MQTL-containing candidate genes in maize (ortho-mMQTL) were detected. Two maize orthologs of rice, GRMZM2G366919 and GRMZM2G178190, were characterized as natural resistance-associated macrophage protein (NRAMP) genes and considered to be candidate genes. Phylogenetic analysis of NRAMP genes among maize, rice, and Arabidopsis thaliana further demonstrated that they are likely responsible for the natural variation of maize grain zinc and iron concentration.
  
  
  CONCLUSIONS
  Syntenic MQTL-related regions and ortho-mMQTL are prime areas for future investigation as well as for marker-assisted selection breeding programs. Furthermore, the combined method using the rice genome that was used in this study can shed light on other species and help direct future quantitative trait research. In conclusion, these results help elucidate the molecular mechanism that underlies grain zinc and iron concentration in maize.
authors.affiliation: Hebei Branch of Chinese National Maize Improvement Center, Agricultural University of Hebei, Baoding, People's Republic of China. 396796822@qq.com.
authors.forename: Tiantian
authors.initials: T
authors.lastname: Jin
authors.affiliation: Hebei Branch of Chinese National Maize Improvement Center, Agricultural University of Hebei, Baoding, People's Republic of China. jtchen@hebau.edu.cn.
authors.forename: Jingtang
authors.initials: J
authors.lastname: Chen
authors.affiliation: Hebei Branch of Chinese National Maize Improvement Center, Agricultural University of Hebei, Baoding, People's Republic of China. zhuliyiny@126.com.
authors.forename: Liying
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Hebei Branch of Chinese National Maize Improvement Center, Agricultural University of Hebei, Baoding, People's Republic of China. zhaoyongfeng@hebau.edu.cn.
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Hebei Branch of Chinese National Maize Improvement Center, Agricultural University of Hebei, Baoding, People's Republic of China. guojinjie512@163.com.
authors.forename: Jinjie
authors.initials: J
authors.lastname: Guo
authors.affiliation: Hebei Branch of Chinese National Maize Improvement Center, Agricultural University of Hebei, Baoding, People's Republic of China. hyqun@hebau.edu.cn.
authors.forename: Yaqun
authors.initials: Y
authors.lastname: Huang
mesh_terms: D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D012275:Oryza / Q000235:genetics*; D040641:Quantitative Trait Loci; D003313:Zea mays / Q000235:genetics*; D015032:Zinc / Q000378:metabolism
chemical_list: D015032:Zinc