Proteomic Analysis Of Rice Seedling During The De-Etiolation Process And Its Uppermost Internodes At Milky Stage

Rice, which is widely cultivated in China, plays important roles in the agricultural production. Besides, it is a model monocot for genome study. Great successes have been made in structural genomics, which would drive the life science forward unprecedentedly. In the post genome era, proteomics is becoming a hotspot. It concerns about both the dynamic expression and the interaction of proteins. Classical proteomic approaches including high resolution two-dimensional electrophoresis (2-DE), matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/MS) and bioinformatics technique were used in this presentation. Basic proteomics of the rice uppermost internodes, comparative proteomics of the rice seedling in the de-etiolation process were studied using this strategy, in order to identify some uppermost internodes specific and dark or light responsive proteins. It would benefit to both production and theory. Proteome maps were constructed for the 2-week old etiolated rice seedlings and the uppermost internodes of rice at milky stage. Totally, 185 proteins were analyzed through MALDI-TOF MS and database searching. Among them 149 proteins were identified. The success ratio of protein identification was 80.5% much more than that in wheat and maize. The identified proteins were the products of 118 genes, and could be sorted into 13 functional categories. Most of them involved in energy production and primary metabolism processes. Meantime, many defense proteins were also among them. Among those accumulated in uppermost internodes, energy production and metabolism associated proteins such as triose-phosphate isomerase, phosphoglucomutase accounted for more than 37%, which indicated a high metabolic activity in this tissue. Beta-tubulins, inorganic pyrophosphatase and vacuolar proton-ATPase accumulated abundantly. They are all beneficial to cell division and enlargement of the rice uppermost internodes. UDP-glucose pyrophosphatase's accumulation indicated the biosynthesis of storage and structural glucan. Many signaling and defense proteins, such as G protein, GPI, phenylalanine ammonia-lyase (PAL), GST, APX, SOD to name a lot, were also abundant in this tissue at the milky stage. It could be deduced that the rice uppermost internode at the milky stage can sense and transfer the environmental information immediately. So it can start the defense reaction rapidly under stress and decrease the negative effects at most. During the de-etiolation process, proteins of the rice seedlings that could be resolved with 2-DE technique reduced gradually with the illumination. Proteins such as triosephosphate isomerase, succinyl-CoA ligase, isovaleryl-CoA dehydrogenase and ATPase decreased after the illumination, which indicated that growth of the rice seedlings in darkness is a great matter and energy consumption process. Moreover, α-oxidation of fatty acid might exist in the etiolated rice seedlings for the abundant accumulation of fatty acid alpha-oxidase. At the same time, Guanine nucleotide-binding protein beta subunit-like protein (GPB-LR) (RWD), 20S proteasome and Bowman Birk trypsin inhibitor changed in the same way as catabolic proteins. This implied that darkness should have stress effect on rice seedling growth. After illumination, the accumulation of anabolic proteins increased. The change pattern of the enzymes involved in the chlorophyll biosynthesis pathway suggested that there were negative feedback of the product in this pathway. We first applied proteome method to study the proteins expression pattern of the rice uppermost internodes and etiolated seedlings responding to light. Valuable information of some proteins was acquired. This would contribute to the understanding of the growth and function of rice uppermost internodes, mechanism of dark stress,de-etiolation and photosynthesis.