Proteomic analysis of nitrogen stress-responsive proteins in two rice cultivars differing in N utilization efficiency
Plant nitrogen utilization efficiency (NUE) has become critical important in modern agriculture, not only for crop growth and yield but also for reducing production cost. Moreover, one of the major negative environmental impacts of agricultural activities is associated with excessive nitrogen application. Improving NUE will ensure lower level of N fertilizer usage thus reduce environmental contamination. In order to understand the NUE mechanism of rice, the largest food crop in the world, a systematic proteomic study of investigating the nitrogen stress-responsive proteins in two rice cultivars differing in NUE is conducted. Four leaf-old seedlings were treated with normal nutrition solution and N-free solution for 12 h, 3 d and 7 d. Total proteins of leaves were extracted and separated by two-dimensional gel electrophoresis. Although more than 1000 protein spots were reproducibly detected, only a very small proportion of spots showed differential expression, including 10 and 24 up-regulated, 2 and 12 down-regulated in the two cultivars Chunyou 58 and Yongyou 6, respectively. This indicates that relatively simply biochemical pathways maybe involved with NUE thus the NUE as a trait maybe efficiently manipulated. Mass spectrometry based peptide mass fingerprinting (PMF) procedure identified 31 protein spots. Six stress-induced proteins were found, including DegP2, harpin binding proteins, Heat shock-related proteins, glutathione S-transferase GSTF14, Fibrillin-like protein and Glyceraldehyde-3-phosphate dehydrogenase. Apart from the stress related proteins, the other differential proteins identified were mainly these involved in the regulation of the main leaf biological function, photosynthesis metabolism, such as Rubisco activase, RuBisCo large subunit, etc. The study also detected two novel proteins, harpin binding protein and oryzains gamma precursor. The current study reveals new insights into N stress response and theoretical bases for improving NUE of rice crop.