| Maize(Zea mays L.)is one of the most important food crops in the world.Drought is the major abiotic stress that negatively influences growth and yield of maize and other cereal grain crops.A multitude of genes and pathways tightly modulate plant growth,development and responses to environmental stresses including drought.Despite recent scientific headway in deciphering maize drought stress responses,the overall picture of key proteins and genes and pathways regulating maize big trumpet mouth stage(V12)drought tolerance is still fragmented.The purpose of this study is to improve the understanding of plant drought resistance response and to meet the needs of crop drought resistance breeding.It is of great significance for drought resistance breeding of maize by studying drought resistance mechanism of maize at large trumpet mouth stage and searching for genes and metabolic pathways related to drought resistance.In this study,two maize hybrid cultivars with different drought resistance(drought tolerant ND476 and drought sensitive ZX978)were used as materials to conduct 12-day water stress from the small bell-mouth stage to the large bell-mouth stage(V12),determine soil moisture every other day until field soil moisture content monitoring treatment group reached 5%-10%and measure the changes of photosynthetic rate indexes and its related physiological and biochemical indexes during the period of drought stress treatment.The mechanism of drought resistance of maize in large trumpet was discussed by combining with the results of transcriptome sequencing.Real-time fluorescence quantitative technology was used to verify the accuracy of transcriptome sequencing results,and proteomic analysis was used to support transcriptome results.Key genes related to drought resistance in maize V12 stage were screened and cloned.The main results are as follows:(1)Through the sequence analysis of four maize transcriptome(two cultivars,two treatments),81.03 GB of clean data was obtained from 10 samples,with a total of 54.127 million reads,with an average of 46.51 million clean reads per sample.Ten samples of clean reads were compared with maize reference genome B73.The percentage of Q30 base is over 96.0%,and the comparison rate is from 89.62%to 92.91%.(2)Through the analysis of RNA-seq data,3114 DEGs were identified,21 of which were specifically expressed in the drought resistant cultivar ND476.Among them,the genes involved in secondary metabolite biosynthesis,proline biosynthesis,transcription factor regulation,detoxification and stress defense were all highly expressed in ND476.By qRT-PCR analysis,the real-time quantitative results of 20 genes distributed in four different key regions were same to the expression patterns in RNA-seq data.(3)The results of physiological analysis confirmed the RNA-seq data.ND476 showed better water holding capacity,higher soluble protein content,peroxidase activity and lower lipid peroxidation than ZX978.(4)873 differential abundance proteins(DAPs)were identified by comparing the proteome.Among them,there are 49 DAPs in ND476 and 64 DAPs in ZX978.DAPs of ND476 were enriched in endoplasmic reticulum protein processing and secondary metabolic biosynthesis pathway.The drought-resistant cultivar ND476 showed stronger drought tolerance in transcription and protein levels.(5)The selected 11 key DEGs were used as candidate genes to clone the key gene dnaj6 chaperone protein of ND476 in response to drought stress,which laid a foundation for subsequent functional verification.In this study,the physiological and biochemical characteristics and differentially expressed genes of different drought-resistant maize varieties in the big trumpet mouth stage were analyzed by using physiological biochemistry,transcriptomics and proteomics,and some drought-resistant genes were discovered,which laid a theoretical foundation for drought-resistant genetic improvement molecular breeding of maize. |
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