Abstract
The carnivorous plants of the genus Drosera grow on nitrogen-limited wetlands. Year-round measurements showed that the nitrate concentrations in the habitats of D.routundifolia (Dr), D.spathulata (Ds) and D.tokaiensis (Dt) were 0~3.3 μM (av.0.9 μM), 3.1~39.7 μM (av.15.0 μM) and 0 ~148 μM (av.43.0 μM), respectively, suggesting that Dt and Ds prefer higher nitrate concentrations than Dr. Since Dt has been shown to originate from a natural cross between Dr and a closely related species Ds, we compared the response of the three species to different nitrogen conditions in the greenhouse and found that Dt and Ds are more tolerant to nitrogen than Dr is (2009 annual meeting). In an effort to analyze the cause of the different tolerance to nitrogen, we isolated and characterized nitrate reductase (NR) and nitrite reductase (NiR) cDNAs from the Drosera species. The predicted amino acid sequences of NR and NiR molecular species were used to construct unrooted phylogenetic trees. The phylogenetic trees of NR and NiR were distinct from that of RbcL, suggesting ancient origin of the Drosera-Type NR and NiR proteins in the evolution of angiosperms.
