Analysis Of Two-component Signal Transduction Systems And Transcriptional Regulators In The Model Cyanobacterium Synechocystis Sp.PCC 6803 Using Metabolomic Approach

This study focused on two types of regulatory proteins in model photosynthetic cyanobacterium,Synechocystis sp.PCC 6803.As the most abundant signal transduction systems in Synechocystis,two-component transduction systems play important roles in regulating responses to environmental disturbances.However,due to the complexity of the systems and functional coupling between different response regulators,the specific functional diversity of many response regulators are still lack of exploration.In addition,only a few transcriptional regulators have been clearly functionally annotated,and the results showed that they are widely involved in the regulation of physiological activities;meanwhile,most transcriptional regulators are still functionally unknown.Metabolomics developed in recent years,which can be applied to identify many small molecules in cells and determine the differences of them between samples and states,are widely used in the identification and analysis of various microbial gene functions.First,a GC-MS based comparative metabolomic analysis was performed on a library of knockout mutants for 44 response regulators(RRs)in Synechocystis.The metabolomic profiling analysis showed that 7 RRs mutants were significantly different at the metabolomic level,although their growth patterns were similar to the wild type under the normal autotrophic growth condition,suggesting regulatory diversity of RRs at metabolite level in Synechocystis.Additionally,a detailed metabolomic analysis coupled with RT-PCR verification led to useful clues for possible function of these 7RRs,which were found involved in the regulation of multiple aspects of cellular metabolism in Synechocystis.Moreover,an integrative metabolomic and evolutionary analysis of all RRs showed that 4 groups of RR genes clustered together in both metabolomic and evolutionary trees,suggesting of possible functional conservation of these RRs during the evolutionary process.Meanwhile,6 groups of RRs with close evolutionary origin were found with different metabolomic profiles,suggesting possible functional changes during evolution.In contrast,more than 10 groups of RR genes with different clustering patterns in the evolutionary tree were found clustered together in metabolomics-based tree,suggesting possible functional convergences during the evolution.Second,a LC-MS analysis to compare the phenotypes and metabolic profiles of32 knock-out mutants encoding transcriptional regulators was conducted.Among them,four mutants were different from the wild type in growth,but most of them showed visibly changes at metabolite level,indicating the function diversity of TRs in Synechocystis.In addition,through the integrative analysis of metabonomic and gene families identified five special groups of TR genes,and each of them shared a proximate relationship in the gene family and metabolomic profiling clusters,indicating the function convergence in evolution.In addition,there are more gene groups that are very different in the evolution,but the TR mutants showed significant similarity in metabolomic profiles,indicating the functional diversity between TRs in evolution.These two types of regulatory proteins play important regulatory roles in various physiological process in Synechocystis,though with different functions.Our study of RRs and TRs provided new insights into the regulatory mechanism of Synechocystis.