title: Genotypic differences in Al resistance and the role of cell-wall pectin in Al exclusion from the root apex in Fagopyrum tataricum.
abstract: OBJECTIVE
  Aluminium (Al) toxicity is one of the factors limiting crop production on acid soils. However, genotypic differences exist among plant species or cultivars in response to Al toxicity. This study aims to investigate genotypic differences among eight cultivars of tatary buckwheat (Fagopyrum tataricum) for Al resistance and explore the possible mechanisms of Al resistance.
  
  
  METHODS
  Al resistance was evaluated based on relative root elongation (root elongation with Al/root elongation without Al). Root apex Al content, pectin content and exudation of root organic acids were determined and compared.
  
  
  RESULTS
  Genotypic differences among the eight cultivars were correlated with exclusion of Al from the root apex. However, there was a lack of correlation between Al exclusion and Al-induced oxalate secretion. Interestingly, cell-wall pectin content of the root apex was generally lower in Al-resistant cultivars than in Al-sensitive cultivars. Although we were unable to establish a significant correlation between Al exclusion and pectin content among the eight cultivars, a strong correlation could be established among six cultivars, in which the pectin content in the most Al-resistant cultivar 'Chuan' was significantly lower than that in the most Al-sensitive cultivar 'Liuku2'. Furthermore, root apex cell-wall pectin methylesterase activity (PME) was similar in 'Chuan' and 'Liuku2' in the absence of Al, but Al treatment resulted in increased PME activity in 'Liuku2' compared with 'Chuan'. Immunolocalization of pectins also showed that the two cultivars had similar amounts of either low-methyl-ester pectins or high-methyl-ester pectins in the absence of Al, but Al treatment resulted in a more significant increase of low-methyl-ester pectins and decrease of high-methyl-ester pectins in 'Liuku2'.
  
  
  CONCLUSIONS
  Cell-wall pectin content may contribute, at least in part, to differential Al resistance among tatary buckwheat cultivars.
authors.affiliation: Key Laboratory of Conservation Biology for Endangered Wildlife, Ministry of Education. and State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Jian Li
authors.initials: JL
authors.lastname: Yang
authors.forename: Xiao Fang
authors.initials: XF
authors.lastname: Zhu
authors.forename: Cheng
authors.initials: C
authors.lastname: Zheng
authors.forename: Yue Jiao
authors.initials: YJ
authors.lastname: Zhang
authors.forename: Shao Jian
authors.initials: SJ
authors.lastname: Zheng
mesh_terms: D000535:Aluminum / Q000378:metabolism / Q000633:toxicity*; D002473:Cell Wall / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D019612:Fagopyrum / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D005838:Genotype; D010368:Pectins / Q000737:chemistry / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
chemical_list: D010368:Pectins; D000535:Aluminum