Abstract
Model plants and crops are usually grown with excessive supply of nitrate. To understand the physiology of wild plants and algae, however, examination of the effects of low-level nitrate is important. We will demonstrate this by two examples. (1) In cyanobacteria, expression of the genes related to nitrate assimilation is induced by 2-oxoglutarate, which accumulates upon nitrogen limitation, and activated by the nitrite resulting from nitrate reduction. We found that the nitrite-responsive gene activation is essential for survival specifically under nitrate-limited conditions. (2) The carnivorous plants Drosera rotundifolia (Dr) and D. spatulata (Ds) were sensitive to 5 mM nitrate, whereas D. tokaiensis (Dt; a Dr/Ds hybrid) was not. The average nitrate concentrations in the natural habitat of Dr and Dt were 1 μM and 48 μM, respectively, suggesting that Dr prefers strictly nitrate-limited conditions. The increasing Dt population may be related to NOX-containing precipitation.
