| Low seed vigor results in the poor storage resistance and field performance.The exploration of physiological and biochemical characteristics and related genes of seed vigor is helpful to reveal the regulation mechanism of seed vigor and provide the theoretical basis for the selection of new sweet corn varieties with high seed vigor.In this study,21 sweet corn inbred lines with various seed vigor were used as experimental materials.Through natural aging and artificial accelerated aging treatments,the seed vigor related traits,physiological and biochemical indexes under the two aging methods were compared to verify whether artificial accelerated aging can simulate the seed aging under natural conditions.Then two sweet corn inbred lines with large differences in seed vigor were selected to analyze using transcriptome sequencing technology,and to mine the regulatory genes of sweet corn seed vigor.This study aimed to preliminarily analyze and predict of physiological and biochemical changes and regulatory networks associated with seed vigor in sweet corn.The results of this study are as follows:1.The seeds of 21 sweet corn inbred lines were naturally aged for 2,4 and 6 months respectively.The related traits of seed vigor including Germination Potential(GP),Germination Rate(GR),Germination Index(GI),Vigor Index(VI)and Seedling Fresh Weight decreased with the aging time.The mean value of VI ranged from 14.81 to 37.48.After 6 months of natural aging,the activities of five biochemical enzymes,such as Superoxide Dismutase(SOD),etc.,were detected with the mean value range from 243.89 to 3154.65;the contents of Malondialdehyde(MDA),Total Starch(TS),Total Protein(TP),Gbberellin(GA)and Abscisic Acid(ABA)were detected,with the average range from53.03 to 1650.81.The scanning electron microscope observation revealed that the starch granules of low-activity seeds were loosely arranged and decomposed.2.The seeds of 21 sweet corn inbred lines were artificially accelerated aged for 0,4and 6 days respectively.The related traits of seed vigor including GP,GR,GI,VI and Seedling Fresh Weight decreased with the aging time.The mean value of VI ranged from1.60-37.06.After 6 days of artificial aging,the activities of five biochemical enzymes,such as SOD,etc.,were detected with the mean value range from 4.55 to 2844.59;the contents of MDA,TP,TS,GA and ABA were detected,with the average range from 15.05 to1628.78.3.After the seeds of 21 sweet corn inbred lines were natural aging for 6 months,5seed vigor correlated indexes except GP showed that there were significant differences among materials.10 physiological and biochemical indexes were also very significant among materials.After 6 days of artificial aging,these seed vigor correlated indexes were significantly different in 21 sweet corn inbred lines.10 physiological and biochemical indexes without TP were significantly different among the materials,and there was no significant differences observed between the replications.4.After 2,4 and 6 months of natural aging,the correlation of these seed vigor related indexes was carried out and a significantly positive correlation between different aging treatments were detected,the range of correlation coefficient was 0.47-0.97,and the correlation coefficient between GR and GI of natural aging 6 months was the largest.After0,4 and 6 days of artificial aging,the correlation of these seed vigor related indexes was carried out and a significantly positive correlation between different aging treatments were detected,the range of correlation coefficient was 0.57-0.99,and the correlation coefficient between GR and GI of artificial aging 4 days and artificial aging 6 months was the largest.5.The correlation analysis of 10 physiological and biochemical indexes after artificial accelerated aging for 6 days showed that GA content was significantly positive correlated with GI and VI,with correlation coefficients of 0.46 and 0.50,respectively.While the correlation analysis of 10 physiological and biochemical indexes after natural aging for 6months showed that SOD activity was significantly positive correlated with GR and GI,with correlation coefficients of 0.57 and 0.49,respectively.The results showed that there were differences in seed physiological and biochemical changes between these two aging ways.6.A total of 738 differentially expressed genes,including 301 up-regulated genes and437 down-regulated genes,were identified by transcriptome sequencing using the seeds after 6 months natural aging.In the GO functional annotation and enrichment analysis of differentially expressed genes,a total of 2348 GO Term were annotated,of which 1412 GO Term were annotated to biological processes;650 GO Term were annotated to molecular functions;286 GO Term were annotated to cell components.The top five GO Term with the most differential gene enrichment were Sulfide metabolism,Oxidoreductase activity,Monooxygenase activity,Glutathione metabolism and Cell modified amino acid process.7.This study enriched a GO Term related to the physiological and biochemical changes of seeds,which named oxidoreductase activity and contained 48 differentially expressed genes.5 putative candidate genes were screened out according to the physiological and biochemical changes related to seed vigor.Zm00001d007858 encodes the key enzyme of Vitamin B6 synthesis;Zm00001d008843 encodes the key enzyme to promote Ascorbic Acid regeneration;Zm00001d036135 encodes Superoxide Dismutase.They are all involved in the antioxidant defense pathway of plants.Zm00001d044908 and Zm00001d044906 encode 12-Oxophytodienoate Reductase,which regulates the jasmonic acid pathway in plants and as an effective signal for defense against abiotic stress.These above genes may be the putative key genes involved in the regulation of seed vigor. |
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