AUTHOR=Guo Peng , Qi Yi-Ping , Yang Lin-Tong , Lai Ning-Wei , Ye Xin , Yang Yi , Chen Li-Song 

TITLE=Root Adaptive Responses to Aluminum-Treatment Revealed by RNA-Seq in Two Citrus Species With Different Aluminum-Tolerance

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.00330

DOI=10.3389/fpls.2017.00330

ISSN=1664-462X

ABSTRACT=<p>Seedlings of aluminum (Al)-tolerant <italic>Citrus sinensis</italic> and Al-intolerant <italic>Citrus grandis</italic> were fertigated daily with nutrient solution containing 0 and 1.0 mM AlCl<sub>3</sub>●6H<sub>2</sub>O for 18 weeks. The Al-induced decreases of biomass and root total soluble proteins only occurred in <italic>C. grandis</italic>, demonstrating that <italic>C. sinensis</italic> had higher Al-tolerance than <italic>C. grandis</italic>. Under Al-treatment, <italic>C. sinensis</italic> roots secreted more citrate and malate than <italic>C. grandis</italic> ones; less Al was accumulated in <italic>C. sinenis</italic> than in <italic>C. grandis</italic> leaves. The Al-induced reduction of phosphorus was lesser in <italic>C. sinensis</italic> roots and leaves than in <italic>C. grandis</italic> ones, whereas the Al-induced increase of sulfur was greater in <italic>C. sinensis</italic> roots and leaves. Using RNA-seq, we isolated 1905 and 2670 differentially expressed genes (DEGs) from Al-treated <italic>C. sinensis</italic> than <italic>C. grandis</italic> roots, respectively. Among these DEGs, only 649 DEGs were shared by the two species. Further analysis suggested that the following several aspects conferred <italic>C. sinensis</italic> higher Al-tolerance: (a) Al-treated <italic>C. sinensis</italic> seedlings had a higher external Al detoxification capacity <italic>via</italic> enhanced Al-induced secretion of organic acid anions, a higher antioxidant capacity and a more efficient chelation system in roots; (b) Al-treated <italic>C. sinensis</italic> seedlings displayed a higher level of sulfur in roots and leaves possibly due to increased uptake and decreased export of sulfur and a higher capacity to maintain the cellular phosphorus homeostasis by enhancing phosphorus acquisition and utilization; (c) Cell wall and cytoskeleton metabolism, energy and carbohydrate metabolism and signal transduction displayed higher adaptative responses to Al in <italic>C. sinensis</italic> than in <italic>C. grandis</italic> roots; (d) More upregulated than downregulated genes related to fatty acid and amino acid metabolisms were isolated from Al-treated <italic>C. sinensis</italic> roots, but the reverse was the case for Al-treated <italic>C. grandis</italic> roots. These results provide a platform for further investigating the roles of genes possibly responsible for citrus Al-tolerance.</p>