Abstract
Under different red (R):blue (B) photon flux ratios, the growth performance of rapeseed (Brassica napus L.) is significantly different. Rapeseed under high R ratios shows shade response, while under high B ratios it shows sun-type morphology. Rapeseed under monochromatic red or blue light is seriously stressed. Transcriptomic and proteomic methods were used to analyze the metabolic pathway change of rapeseed (cv. "Zhongshuang 11") leaves under different R:B photon flux ratios (including 100R:0B%, 75R:25B%, 25R:75B%, and 0R:100B%), based on digital gene expression (DGE) and two-dimensional gel electrophoresis (2-DE). For DGE analysis, 2054 differentially expressed transcripts (|log(2)(fold change)|≥1, q<0.005) were detected among the treatments. High R ratios (100R:0B% and 75R:25B%) enhanced the expression of cellular structural components, mainly the cell wall and cell membrane. These components participated in plant epidermis development and anatomical structure morphogenesis. This might be related to the shade response induced by red light. High B ratios (25R:75B% and 0R:100B%) promoted the expression of chloroplast-related components, which might be involved in the formation of sun-type chloroplast induced by blue light. For 2-DE analysis, 37 protein spots showed more than a 2-fold difference in expression among the treatments. Monochromatic light (ML; 100R:0B% and 0R:100B%) stimulated accumulation of proteins associated with antioxidation, photosystem II (PSII), DNA and ribosome repairs, while compound light (CL; 75R:25B% and 25R:75B%) accelerated accumulation of proteins associated with carbohydrate, nucleic acid, amino acid, vitamin, and xanthophyll metabolisms. These findings can be useful in understanding the response mechanisms of rapeseed leaves to different R:B photon flux ratios.