Comperative Proteomics Of Manihot Esculenta Leaves Under Different Light Conditions

Cassava (Manihot esculenta Crantz) is native to South America Amazon River Basin, which is an important energy crop with high content of starch, and one of the major economic food crops in the tropical region. Cassava is a C3plant, but it has higher net photosynthetic rate than other C3plants. In cassava, there is some cell structure similar to vascular bundle sheath cells of C4plants. Furthermore, C4photosynthetic enzymes is effective in Cassava, so it has been considered as a typical C3-C4intermediate type, which has photosynthesis production potential. Studying the molecular mechanism of the high photosynthetic efficiency control of Cassava leaf is meaningful to improve the quality, the photosynthetic capacity of cassava, and to cultivate high-starchy Cassava via Biological technology.The study was based on comperative proteomics of No.8Southern China cassava (SC8) leaf. Explore the change pattern of proteome ofcassava leaves under different conditions of light (normal illumination, constant light, conditons weak light) to get the key protein or enzyme related to effective light regulation in Cassava. The results are as follows:1、The result of dating the content of soluble sugar, starch, and chlorophyll of Cassava under the condition of light stress show that light stress had no significant effect on the soluble sugar content of blades of Cassava and it maintains at similar level.however, content of starch, and chlorophyll can be greatly influenced so that the content of them reduced a lot under the condition of coverage, though they can keep a stable level under the condition of control and light treatment.2、According to analyse2-DE gels of cassava leaves under the conditions of light stress, we found177protein spots that is significantly different in expression, via MALDI TOF MS and MALDI TOF-TOF MS MS identification,127protein spots were successfully identified. If we attached COG analysis to the identified proteins, differentially expressed proteins can be mainly divided into10categories, among them, post-translational modifications, protein folding and molecular chaperones, carbohydrate transport and metabolism, and energy conversion function protein accounted for the major part. We could draw the following conclusions via localization of protein subcellular and GO analysis:the proteins involving ATP binding and ribulose1,5-bisphosphate carboxylase activity molecular function accounted for more than40, most of these proteins is positioning chloroplast, showing that light stress had a significant impact on processing of cassava chloroplast. Meanwhile, some proteins of cassava leaves also are regulated by light, and light stress can induce some protein expression of the cassava leaves increase to adapt to light stress environment. Synthesis and metabolism of amino acids affect various aspects of plant growth and development, under stress in the light cysteine synthase and glutamine synthetase, which are a key enzyme involved in the plants of sulfur and nitrogen metabolism, can be affected a lot by light stress.we can conduct in-depth study of these two enzymes from the angle of the light regulation to reveal the molecular mechanisms involved in light-regulated process, which may improve plant take advantage of the efficiency of mineral elements and increase the antioxidant capacity of the plant, as well as enhance the ability to adapt to the environment. It should have important significance.3、Blast2Go analysis found that the differences expression proteins distribution in40of metabolic pathways, among whichs carbon fixation in photosynthetic organisms, glyoxylate and dicarboxylate metabolism, oxidative phosphorylation, glutathione metabolism, glycolysis/Gluconeogenesis, starch and sucrose metabolism were the main pathways. Carbon fixation in photosynthetic organisms is relatively active participation protein18, related enzymes of6, indicating that the photosynthetic carbon metabolism pathway important physiological and biochemical changes in response to different light.4、According to analysis of sources of protein species identified by mass spectrometry,18protein spots were found which are belong to the cassava species, we selected the ATP synthase beta subunit, ribulose1,5-bisphosphate carboxylase,14-3-3proteinand cassava flax bitter glycoside hydrolase (linamarase) four protein to verify the level of gene expression and laws of various gene expression patterns by RT-PCR. The results found that under the stress conditions, part of the level of gene expression changes keep part pace with protein expression changes, for instance,14-3-3proteins under control and light treatment, the level of gene expression and protein expression levels are relatively similar., but in blackout conditions, the protein level and gene level upregulation to some extent. Flax bitter glucoside hydrolase gene expression changes in the levels of protein and gene level expression, changes in gene expression and protein expression changes inconsistently may be due to protein translation (such as alternative splicing, phosphorylation and glycosylation and so on) the lead.This study is based on the observation of physiological and biochemical cassava under different light conditions, the use of comparative proteomics research methods identified a number of possible cassava leaf protein associated with photosynthesis, using RT-PCR validation and comparison of the cassava leaves protein and gene inspatiotemporal expression characteristics under different light conditions. Research results to further explore and cassava high luminous efficiency function of the role of genes in cassava leaves law provides the basis to further explore the regulatory mechanism of cassava high light efficiency and cassava molecular breeding data reference.