The transcriptome variations of Panaxnotoginseng roots treated with different forms of nitrogen fertilizers.

BACKGROUND
The sensitivity of plants to ammonia is a worldwide problem that limits crop production. Excessive use of ammonium as the sole nitrogen source results in morphological and physiological disorders, and retarded plant growth.

RESULTS
In this study we found that the root growth of Panax notoginseng was inhibited when only adding ammonium nitrogen fertilizer, but the supplement of nitrate fertilizer recovered the integrity, activity and growth of root. Twelve RNA-seq profiles in four sample groups were produced and analyzed to identify deregulated genes in samples with different treatments. In comparisons to NH[Formula: see text] treated samples, ACLA-3 gene is up-regulated in samples treated with NO[Formula: see text] and with both NH[Formula: see text] and NO[Formula: see text], which is further validated by qRT-PCR in another set of samples. Subsequently, we show that the some key metabolites in the TCA cycle are also significantly enhanced when introducing NO[Formula: see text]. These potentially enhance the integrity and recover the growth of Panax notoginseng roots.

CONCLUSION
These results suggest that the activated TCA cycle, as demonstrated by up-regulation of ACLA-3 and several key metabolites in this cycle, contributes to the increased Panax notoginseng root yield when applying both ammonium and nitrate fertilizer.