| Fresh waxy corn has a short growth cycle and a high replanting index,but it is susceptible to cold wave when planting in early spring,late autumn and winter planting,which affects the germination and seedling emergence,thus affecting the yield and annual production of waxy corn.Therefore,it is of great theoretical significance to study the germination mechanism of waxy corn at low temperature.In this study,two waxy maize inbred lines with low temperature tolerance and low temperature sensitivity were selected through the dynamic changes of physiological indicators of 41 waxy maize inbred lines during germination under low temperature stress,and the differential genes and differential metabolites of the transcriptome and metabolome of waxy maize during germination under low temperature stress were analyzed,while the molecular mechanism of regulatory network of the low temperature stress response of waxy maize was studied.The following results were obtained:1.Germination of 41 waxy maize inbred lines at normal temperature was used as controlled experiment.When germinating at low temperature(15°C),the germination rate,vigor index,bud length,root length,fresh weight and dry weight of N28 and N67 reached significant difference level,and the germination potential,germination speed index and root length reached extremely significant difference level,while no significant differences were found in the phenotypic parameters during germination at normal temperature.2.After 0 h,24 h,48 h,72 h and 96 h of low temperature stress,the results showed that the physiological indexes such as SOD,POD,CAT,malondialdehyde,proline,soluble sugar and conductivity of N67 and N28 increased,and the conductivity and malondialdehyde content of N67 increased faster than those of N28,while the other indexes increased more slowly.The conductivity and malondialdehyde content of N67 were significantly higher than those of N28,while the superoxide dismutase,catalase,peroxidase,proline and soluble sugar contents of N28 were higher than those of N67.These physiological and biochemical substances could eliminate the harmful substances accumulated under plant stress and enhance the stress tolerance of plants.3.There were 1,682 and 1,778 distinct differential genes produced by N28 and N67 during germination under low temperature stress,respectively.361 differential genes were present in both inbred lines,1,320 differential genes were only present in N28,and 1,416 differential genes were only present in N67.KEGG enrichment showed that differential genes on germination of N28 and N67 at low temperature were mainly enriched in metabolic pathways,biosynthesis of secondary metabolites,plant hormone signal transduction,plant MAPK signaling pathways,starch and sucrose metabolism,ATP-binding cassette transporter family,flavonoid biosynthesis,and TCA cycle pathways.GO classification statistics of differential genes revealed that differential genes mainly accounted for a high proportion in 13 pathways including membrane and membrane components,cell and cell components,organelle and organelle components,catalytic activity and binding function,metabolic processes,biological regulatory processes,stimulant response processes,and biological regulatory processes.GO enrichment analysis showed that differential genes were significantly enriched mainly in photosynthetic membrane,chloroplast membrane,plasma membrane,photosynthesis,endoderm part,endosome membrane,flavin adenine dinucleotide binding pathway,stimulator detection pathway and coated vesicle membrane pathway.4.There were 27 and 11 distinct differential metabolites produced during germination under low temperature stress in N28 and N67,respectively,and three differential metabolites were present in both inbred lines,24 differential metabolites were only present in N28 and eight differential metabolites were only present in N67.Cluster analysis of differential metabolites on germination of N28 and N67 at low temperature showed that the contents of phenolic acid methyl ferulate,lipid substance 9-hydroxy-12-oxo-10-octadecenoic acid and organic acid substance sea cucumber were very high in N28 but very low in N67.KEGG enrichment analysis revealed that 27 differential metabolites produced by N28 under low temperature stress: 3 differential metabolite were enriched in the ATP-binding cassette transporter family;3 enriched in the secondary metabolite biosynthesis pathway,6 enriched in the metabolic pathway,and 1 enriched in the pentose and glucuronic acid interconversion pathway.11 differential metabolites produced by N67 under low temperature stress: 2 differential metabolites were enriched in the ATP-binding cassette transporter family,2 enriched in the biosynthesis pathway of secondary metabolites,and 2 enriched in the metabolic pathway.The differential metabolites of the two materials were most significantly enriched in the ATP-binding cassette transporter family,followed by the biosynthetic pathway of secondary metabolites,and N67 was more significantly enriched than N28,indicating that low temperature stress had a greater effect on metabolic pathways,especially secondary metabolic pathways,during seed germination in waxy maize.5.Cluster analysis showed that differential genes and differential metabolites produced by N28 and N67 under low temperature stress mainly clustered in alkaloids,amino acids and their derivatives,flavonoids,lignans and coumarins,lipids,nucleotides and their derivatives,organic acids,phenolic acids and other substances.KEGG pathway analysis showed that N28 was enriched to 68 differential genes and 3 differential metabolites in the ATP-binding cassette transporter family pathway;N67 was enriched to 74 differential genes and 2 differential metabolites.ATP-binding cassette transporter family pathway correlation network analysis revealed that N28 was enriched to 3 differential genes(Zm00001d018291、Zm00001d048621、Zm00001d040562)corresponding to 1 differential metabolite(pme3732)in this pathway,and there was a negative correlation between differential genes and differential metabolites;N67 was enriched in 2 differential genes(Zm00001d013254 、Zm00001d053612)corresponding to 2 differential metabolites(mws0219、mws0668)one by one in this pathway,and there was a positive correlation between differential genes and differential metabolites.The results can be used as a reference for studying the mechanism of low-temperature germination of waxy corn. |
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