Transcriptomic Analysis On Roots Of Sorghum Reponding To Low Phosphorus And Functional Study Of Sbpht1 Family

Sorghum(Sorghum bicolor)is an important crop for important feed crop.Sweet sorghum has higher yield of dry matter,crude protein and digestible dry matter than that of corn silage in the lower farming region of the Yangtze River.However,the deficiency of available phosphorus in the middle and lower reaches of Yangtze River,lead to that a large amount of phosphorus fertilizer is needed to cultivate high-yield feed crops.Therefore,research on the mechanism of sorghum responding to low-P stress and how to improve the absorption and utilization rate of low-concentration P by plants has a significant impact on the development of animal husbandry in China.In this study,firstly,we comprehensively evaluated the low-P tolerance of 29 sorghum accessions identify the two accessions with lowP tolerance and low-P sensitivity respectively.Secondly,low-P tolerance related genes were characterized based on the RNA-seq results of two accessions' root.Finally,genes of Pht1 family in sorghum were cloned and functionally analyzed.The main results are as follows:1?Comprehensive evaluation of sorghum low-P toleranceThough the two-year pot experiment,agronomic characters,biomass and phosphorus efficiency correlation indexes of 29 sorghum accessions were measured,and low-P tolerance coefficients of them were calculated.The results indicated that using different indicators to evaluate the low-P tolerance of sorghum would perform different results.The low-P tolerance of sorghum accessions could be comprehensively evaluated though the comprehensive lowP tolerance index calculated by principal component analysis.In this study,S19 and S26 were identified as low-P-tolerance and low-P-sensitive accessions using principal component analysis,respectively.2?Response of sorghum root morphology to low-P stressThe correlation between the low-P tolerance coefficients of root morphology and the value of comprehensive low-P tolerance of sorghum accessions showed that,the relationship between root morphology and low-P tolerance of sorghum is closely.Results of the changes of S19 and S26 root morphology under low-P stress showed that:the number of lateral roots of S19 increased significantly compared with the control,while that of S26 decreased significantly,which suggested that the increase of lateral roots is a strategy for sorghum to improve low-P tolerance.3?Transcription response to low-P stress of sorghums rootsThe roots of seedlings grown under low-P and sufficient-P conditions for 8 days were selected for RNA-seq analysis,though analysis of the R/S ratio of S19 and S26 treatments with different P levels(sufficient-P and low-P)under different treatment time by hydroponics experiment.Through comparative analysis,6571 differentially expressed genes(DEGs)in response to low-P stress,4762 DEGs in different accessions under low-P conditions of sorghum roots,and 2089 common DEGs from first two parts named candidate genes related to low-P tolerance in sorghum were obtained.Further analysis found that:(1)The results of analysis of the DEGs in response to low-P stress of S19 and S26 showed that the number of up-regulated and down-regulated DEGs of low-P-tolerant accession are more than that of low-P-sensitive accession.It means that the response of lowP-tolerant sorghum accession to low-P stress was more active.(2)The results of GO and KEGG analysis showed that,the function of candidate genes for low-P tolerance involves biological processes,cellular components,and molecular functions,and candidate genes were enriched to 11 pathways,including secondary metabolism,amino acid metabolism,carbon metabolism,energy metabolism,signal transduction,lipid metabolism and other related pathways.These results implyed that a complex mechanism of low-P tolerance exists in sorghum.(3)The results of the plant hormone signal transduction related genes and transcription factors analysis showed that auxin(AUX),abscisic acid(ABA),jasmonate(JS),ethylene(ETH)and salicylic acid(SA)signal transduction pathways play important roles in the lowP tolerance of sorghum.A total of 127 transcription factors including bHLH,WRKY and MYB may play a role in regulating the low-P tolerance of sorghum.(4)Phosphorus transporter is the carrier of phosphorus uptake and transport.Phosphorus transporters in response to low-P stress of S19 and S26 are mainly Pht1 family.Among them,Sb01g020580,Sb01g046890 and Sb07g023780 all responded positively to low-P stress in the roots of the two accessions,and Sb01g020570 had the highest expression levels under sufficient-P and low-P conditions,suggesting that they might play an important role in phosphorus balance under low-P stress in sorghum.4?Cloning and functional analysis of SbPht1 family genes11 SbPht1genens were found in sorghum genome using bioinformatics analysis,nine of which were cloned in this study.All the nine SbPht1 proteins were localized on cytoplasm membrane.Heterologous expression of SbPht1 in yeast cells showed that nine SbPht1 proteins partially complemented the P uptake deficiency of mutant cell.The affinity to P of SbPht1;5,SbPht1;6 and SbPht1;8 were higher than other SbPht1s.The function of SbPht1;8 was investigated through overexpressing in Arabidopsis in this sthdy.Overexpression of SbPht1;8 promoted P uptake and transpotation,and changed the root morphology in Arabidopsis.In general,thouth analyzing the transcription response to low-P stress of roots of sorghum accessions with different low-P tolerance,and studying the gene function of Pht1 family,we provides support for clarifying the molecular mechanism of low-P tolerance,basis for revealing the mechanism of P absorption,and reference for the cultivation of high-quality varieties with low-P tolerance in sorghum by this study.