AUTHOR=Guo Peng , Qi Yi-Ping , Yang Lin-Tong , Ye Xin , Huang Jing-Hao , Chen Li-Song 

TITLE=Long-Term Boron-Excess-Induced Alterations of Gene Profiles in Roots of Two Citrus Species Differing in Boron-Tolerance Revealed by cDNA-AFLP

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00898

DOI=10.3389/fpls.2016.00898

ISSN=1664-462X

ABSTRACT=<p>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 <italic>Citrus sinensis</italic> and <italic>Citrus grandis</italic> 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 <italic>C. grandis</italic> roots. Apparently, <italic>C. sinensis</italic> had higher B-tolerance than <italic>C. grandis</italic>. 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 <italic>Root Hair Defective 3</italic> expression in <italic>C. sinensis</italic> roots, and repressed <italic>villin4</italic> expression in <italic>C. grandis</italic> roots; accordingly, root growth was less inhibited by B-excess in the former; (b) antioxidant systems were impaired in excess B-treated <italic>C. grandis</italic> roots, hence accelerating root senescence; (c) genes related to Ca<sup>2+</sup> signals were inhibited (induced) by B-excess in <italic>C. grandis</italic> (<italic>C. sinensis</italic>) roots. B-excess-responsive genes related to energy (i.e., <italic>alternative oxidase</italic> and <italic>cytochrome P450</italic>), lipid (i.e., <italic>Glycerol-3-phosphate acyltransferase 9</italic> and <italic>citrus dioxygenase</italic>), and nucleic acid (i.e., <italic>HDA19, histone 4</italic>, and <italic>ribonucleotide reductase RNR1 like protein</italic>) 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.</p>