The short-term responses of glutathione and phytochelation synthetic pathways genes to additional nitrogen under cadmium stress in poplar leaves

Earlier it was noticed that the supplementary nitrogen to nutritive solution of the cadmium stressed (Cd-stressed) plants can alleviate the toxic effects of this metal on the plants and improve plant growth performance. But the underlying mechanisms of such detoxification effect of nitrogen were not studied. In this study, a ten-day responses of related nitrogen-synthesized genes including γ-glutamylcysteine synthetase (γ-GCs), glutathione synthetase (ECGs) and phytochelatin synthase (PCs) involved in glutathione (ECG) and phytochelation (PC) synthetic pathways were examined. The plant growth performance and leaf chlorophyll content were examined at the final harvest. It was shown that the supplement of additional nitrogen to poplar plants under cadmium stress could significantly up-regulate the expression levels of γ-GCs, ECGs and PCs genes in plant leaves during the first 12 hours. Furthermore, cadmium stressed plants with additional nitrogen supplement showed significant enhancement in growth performance and increase in leaf chlorophyll content compared to sole cadmium stressed plants. Our results suggest that additional nitrogen could stimulate a short-term defense system in poplar plants through ECG and PC synthetic pathways. It is contribute to the alleviation of the toxic symptoms in polar plants caused by cadmium stress. This study provides a potential method to render harmless cadmium toxicity in stressed plants with nitrogen fertilization.