title: Long-Term Boron-Excess-Induced Alterations of Gene Profiles in Roots of Two Citrus Species Differing in Boron-Tolerance Revealed by cDNA-AFLP.
abstract: Boron (B) toxicity is observed in some citrus orchards in China. However, limited data are available on the molecular mechanisms of citrus B-toxicity and B-tolerance. Using cDNA-AFLP, we identified 20 up- and 52 down-regulated genes, and 44 up- and 66 down-regulated genes from excess B-treated Citrus sinensis and Citrus grandis roots, respectively, thereby demonstrating that gene expression profiles were more affected in the latter. In addition, phosphorus and total soluble protein concentrations were lowered only in excess B-treated C. grandis roots. Apparently, C. sinensis had higher B-tolerance than C. grandis. Our results suggested that the following several aspects were responsible for the difference in the B-tolerance between the two citrus species including: (a) B-excess induced Root Hair Defective 3 expression in C. sinensis roots, and repressed villin4 expression in C. grandis roots; accordingly, root growth was less inhibited by B-excess in the former; (b) antioxidant systems were impaired in excess B-treated C. grandis roots, hence accelerating root senescence; (c) genes related to Ca(2+) signals were inhibited (induced) by B-excess in C. grandis (C. sinensis) roots. B-excess-responsive genes related to energy (i.e., alternative oxidase and cytochrome P450), lipid (i.e., Glycerol-3-phosphate acyltransferase 9 and citrus dioxygenase), and nucleic acid (i.e., HDA19, histone 4, and ribonucleotide reductase RNR1 like protein) metabolisms also possibly accounted for the difference in the B-tolerance between the two citrus species. These data increased our understanding of the mechanisms on citrus B-toxicity and B-tolerance at transcriptional level.
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, College of Resources and Environment, Fujian Agriculture and Forestry UniversityFuzhou, China; Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry UniversityFuzhou, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Guo
authors.affiliation: Institute of Materia Medica, Fujian Academy of Medical Sciences Fuzhou, China.
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Qi
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, College of Resources and Environment, Fujian Agriculture and Forestry UniversityFuzhou, China; Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry UniversityFuzhou, China.
authors.forename: Lin-Tong
authors.initials: LT
authors.lastname: Yang
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, College of Resources and Environment, Fujian Agriculture and Forestry UniversityFuzhou, China; Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry UniversityFuzhou, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Ye
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, College of Resources and Environment, Fujian Agriculture and Forestry UniversityFuzhou, China; Pomological Institute, Fujian Academy of Agricultural SciencesFuzhou, China.
authors.forename: Jing-Hao
authors.initials: JH
authors.lastname: Huang
authors.affiliation: Institute of Plant Nutritional Physiology and Molecular Biology, College of Resources and Environment, Fujian Agriculture and Forestry UniversityFuzhou, China; Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry UniversityFuzhou, China; The Higher Educational Key Laboratory of Fujian Province for Soil Ecosystem Health and Regulation, Fujian Agriculture and Forestry UniversityFuzhou, China.
authors.forename: Li-Song
authors.initials: LS
authors.lastname: Chen
keywords: Citrus grandis; Citrus sinensis; boron-excess; cDNA-AFLP; roots