Identification And Analysis Of Populus Simonii×P. Nigra Pollen Plant Chloroplast Proteome

Forest,which is the most important terrestrial ecosystem,is human's main sustainable resource.In order to manage the existing forest resources effectively,it is essential to further understand the mechanism of trees' photosynthesis.All the biological processes regarding to photosynthesis were performed by the proteins deposited in chloroplast.A systemic tree chloroplast proteomics investigation is undoubtedlty the basis for discovering the mechanism of tree photosynthesis,and this will provide an effective means for such research.In this study, Percoll differential centrifugation was first used to extract chloroplasts from Populus simonii×P.nigra pollen plant leaves,and classic TCA-acetone precipitation method was succedent done to extract the chloroplast proteins.In total of 113 proteins were successfully identified by using shotgun and LC-MS/MS.Among these,35 proteins were originally annotated in database and the remaining 78 proteins were annotated as unknown proteins.By using blast program at http://www.expasy.org and http://www.arabidopsis.org/Blast/index.jsp,their homologs with high similarity in other plant species databases were matched and listed for those unknown proteins.Among these proteins,28 proteins(25%) are encoded by chloroplast directly in virtue of ChloroP predictor tool,and remaining 85 proteins(75%) are nuclear gene products according to annotations in the Swiss-Prot database.However after predicted with ChloroP program,75 proteins possessed evident putative cTPs,the remaining 10 did not.The subcellular location of these proteins identified were also analyzed based on TargetP and other predictor tool,and 14 proteins could not finally be predicted in chloroplasts' fixed location yet. It revearled that these proteins could be localized into 6 cellular component,which includes photosynthesis,glycolysis,plant hormone,lipoid,amino acid,signalling and protein folding, assembly and fate.All of these identified proteins were classified into 23 functional groups according to PPDB database,which covered a wide range of pathways and functions.As far as known,it is the first systemic identification of tree chloroplast proteme.And this investigation will become a cornerstone for further work on populus proteomics.At the same time,it also can make new content on populus haploid genetics and breeding.