Nitrogen Transfer Play an Important Role of Differentially Expressed Protein of Roots in Eucalyptus Urophylla × E. grandis and Dalbergia Odorifera Nursery Seedlings Intercropping System
Abstract Background: The mixing of Eucalyptus with N2-fixing trees is a frequently successful and sustainable cropping practice. In this study, we evaluated nitrogen transfer and conducted a proteomic analysis on seedlings of Eucalyptus and a N2-fixing tree, Dalbergia (D.) odorifera, from intercropping and monocropping systems, to elucidate the physiological effecting and the molecular mechanisms on N transfer of Eucalyptus mixed with D. odorifera. Results: We demonstrated the following: (1) Nitrogen transfer occurred from D. odorifera to E. urophylla × E. grandis by 14.6 %. Interspecific facilitation of N uptake and root growth in E. urophylla × E. grandis was increased in the intercropping system, but the root growth and N absorption of D. odorifera were inhibited. (2) Among differentially expressed proteins was greater than 1.5 times, E. urophylla × E. grandis were found to be up-regulated several proteins for the nitrogen assimilation and enhancing the nitrogen competition, such as the proteins related to tricarboxylic acid/organic transformation, nitrogen metabolism and nitrogen assimilation; it also up-regulated the expression of stress resistant protein for its adaptability. However, the assimilation and metabolism of nitrogen was promoted in D. odorifera through the up-regulation of amino acid metabolism related proteins, and increased the key enzyme abundance of glycolysis pathway in D. odorifera. (3) Importantly, E. urophylla × E. grandis was the beneficiary in the process of N transfer, there were more different proteins involved in the synthesis pathway than that of the metabolic pathway, but there were more functional proteins involved in metabolic degradation in D. odorifera. Additionaly, the two groups of nitrogen compound transporter were found in E. urophylla × E. grandis, i.e. the molecular mechanism of the N transfer from D. odorifera to E. urophylla × E. grandis was explained by proteomics. Conclusions: Our study suggests that N transfer occurred from D. odorifera to E. urophylla × E. grandis and it was affected by the variations in the differentially expressed protein. We anticipate the result can be verified in field experiments for the sustainable development of Eucalyptus plantations.