Sodium nitroprusside affects the level of photosynthetic enzymes and glucose metabolism in Phaseolus aureus (mung bean)

Nitric oxide (NO) is an important signaling molecule in plants. The present study aims to investigate the downstream signaling pathways of NO in plants using a proteomic approach. Phaseolus aureus (mung bean) leaf was treated with sodium nitroprusside (SNP), which releases nitric oxide in the form of nitrosonium cation (NO+) upon light irradiation. Changes in protein expression profiles of the SNP treated mung bean leaf were analyzed by two-dimensional gel electrophoresis (2-DE). Comparison of 2-DE electropherograms revealed seven down-regulated and two up-regulated proteins after treatment with 0.5 mM SNP for 6 h. The identities of these proteins were analyzed by a combination of peptide mass fingerprinting and post-source decay using a matrix-assisted-laser-desorption-ionisation-time-of-flight (MALDI-TOF) mass spectrometer. Six out of these nine proteins found are involved in either photosynthesis or cellular metabolism. We have taken our investigation further by studying the effect of NO+ on glucose contents in mung bean leaves. Our results clearly demonstrated that NO+ rapidly and drastically decrease the amount of glucose in mung bean leaves. Moreover, four out of nine of these proteins are chloroplastic isoforms. These results suggested that chloroplasts might be one of the main sub-cellular targets of NO in plants.