Proteomic analysis of early germs with high-oil and normal inbred lines in maize Zhanji Liu Æ Xiaohong Yang Æ Yang Fu Æ Yirong Zhang Æ Jianbin Yan Æ Tongming Song Æ T. Rocheford Æ Jiansheng Li Received: 3 February 2008 / Accepted: 1 April 2008 / Published online: 4 June 2008 Ó Springer Science+Business Media B.V. 2008 Abstract High-oil maize as a product of long-term selection provides a unique resource for functional genomics. In this study, the abundant soluble proteins of early developing germs from high-oil and normal lines of maize were compared using two-dimensional gel electro- phoresis (2-DGE) in combination with mass spectrometry (MS). More than 1100 protein spots were detected on electrophoresis maps of both high-oil and normal lines by using silver staining method. A total of 83 protein spots showed significant differential expression ([two-fold change; t-test: P \ 0.05) between high-oil and normal inbred lines. Twenty-seven protein spots including 25 non- redundant proteins were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). Functional categorization of these proteins was carbohydrate metabolism, cytoskeleton, pro- tein metabolism, stress response, and lipid metabolism. Three such proteins involved in lipid metabolism, namely putative enoyl-ACP reductase (ENR), putative stearoyl- ACP desaturase (SAD) and putative acetyl-CoA C-acyl- transferase (ACA), had more abundant expressions in high-oil lines than in normal. At the mRNA expression level, SAD, ENR and ACA were expressed at significantly higher levels in high-oil lines than in normal. The results demonstrated that high expressions of SAD, ENR and ACA might be associated to increasing oil concentration in high- oil maize. This study represents the first proteomic analysis of high-oil maize and contributes to a better understanding of the molecular basis of oil accumulation in high-oil maize. Keywords Germ Á High-oil maize Á Proteome Á Real-time PCR Introduction As a special kind of maize with more than 6% oil con- centration in the grain [1], high-oil maize has a larger germ (scutella and embryo) because 85% of the oil is stored in the germ [2]. Recently, it has received increased interest, especially in the developed world, because of its higher caloric content and better protein quality. High-oil maize was developed by human long-term selection. In 1896, scientists at the University of Illinois began the longest ongoing genetic selection experiment to change the kernel composition in terms of protein and oil concentrations [3]. After 100 generations of selection, the oil concentration of Illinois High-oil (IHO) maize reached 20.37%. In China, Song et al. [4] developed a number of high-oil maize populations after 1980. These include Beijing High Oil (BHO) derived from a synthetic with elite Chinese normal lines, the oil concentration of which increased from 4.71% to 13.9% after 15 cycles. These populations were employed to develop elite high-oil lines that were used to produce Chinese high-oil maize hybrids [5]. Oil concentration in maize is a quantitative trait; many genes with minor effects are involved. With the recent Z. Liu Á X. Yang Á Y. Fu Á Y. Zhang Á J. Yan Á T. Song Á J. Li (&) National Maize Improvement Center of China, China Agricultural University, Beijing 100094, China e-mail: lijiansheng@cau.edu.cn Z. Liu Hi-Tech Research Centre, Shandong Academy of Agricultural Sciences, Jinan 250100, China T. Rocheford Department of Crop Sciences, University of Illinois, 1102 S. Goodwin Ave, Urbana, IL 61801, USA 123 Mol Biol Rep (2009) 36:813–821 DOI 10.1007/s11033-008-9250-3