Assessing Genetic Diversity Of Modern Sugarcane Cultivars And Analyzing Expression Level Of Genes Involved In Sugar Metabolism

Modern sugarcane belongs to the Saccharum genus of the tribe Andropogoneae in the grass family(Poaceae).Sugarcane is not only an important crop for sugar production,but also an efficient biofuel crop.Although whole genome sequencing of the Saccharum genus has not been completed yet,genetic diversity of commercial sugarcane in aid of molecular markers has been extensively studied.Constructing the core molecular marker system is helpful to reduce the molecular markers selected to assess saccharum genetic diversity.The analysis of assessment the genetic diversity and similarity of sugarcane cultivars in the USA and China and genetic relationship with progenitors,can provide more reliable information for sugarcane improvement program.In addition,it had not been reported that the analysis of triscriptomes between two different cell types from sugarcane sink was carried out so far.In our work,we obtained a novel microdissection technique,and developed the analysis of the differentiatialy expressed genes in the sucrose metabolism process.The main results of this theis are:A total of 6,149 unique sugarcane SSR primers were identified from all published sugarcane literature.A set of 20 highly polymorohic SSR markers were further screened for assessment of genetic diversity between and within cultivars and progenitor accessions.The core SSR markers were selected with f relatively low number,randomly and evenly distributed in the genome,highly polymorohic and at least 9 polymorphic bands per marker.Genetic diversity and similarity of sugarcane cultivars in the USA and China were assessed using the core SSR markers.The genetic identity was 70.6%between the cultivars in the USA and Chian.Among three groups of possible sugarcane progenitor accessions,the most similar genetic basis was detected between cultivars and S.officinarum,S.robustum comes the second.Gene expression analysis were performed for 8 key enzymes in the process of sucrose metabolism for different periods of sugarcane intenodes in S.spontaneum,S.officinarum and S.robustum.In general,it was observed that SuSy and CeS were expressed the highest level and 3-10 times higher than several other enzymes.Moreover SPP was express the lowest Among three different periods S.officinarum sugarcane stem,the lower expression of SuSy,UGP,CeS and UGD were in young stem than in intermediate mature and mature stem.It was speculated that this results caused by extensive sucrose accumulating in mature stem tissues.Without laser and frozen sections,parenchyma(P)and sclerenchyma(S)cells were separated and captured simple and novel.Pcells were mechanically harvested from the fresh vertical sections of sugarcane immature stem with biological dissection microscope,with RNA extraction using Trizol method.S cells were mechanically harvested from stem vertical sections completely dipped in RNAlater solution,with RNA extraction using PicoPureTM RNA Isolation Kit.The high quality of the total RNA was successfully applied for transcriptome profiling by RNA sequencing.An analysis of differentially expressed genes in sucrose accumulation function is carried out.In general,the expression of SuSy,UGD,SPP,CaS,IN and CeS in the S cells were 2 times higher than in the P cells.Moreover the expression of UGP and SPP barely showed significant difference between the P and S cells.This data set will provide basic information for studying P and S cells differentiation in regulation of sugar matabolism in future.