| Hypergravity treatment affects seed germination and early seedling growth and development,but its physiological and molecular mechanisms,as well as the potential application value of this treatment in horticultural plant cultivation,are not completely clear.In this experiment,a centrifuge was used to simulate a hypergravity environment,and transgenic Arabidopsis seedlings grown for 5 days were treated with a hypergravity of 1000×g.First,the effect of hypergravity treatment on plant gene expression profiles was analyzed.Then,the tomato seeds were centrifuged at 1000×g,2000×g,4000×g,8000×g for 1 h,and the changes in the germination rate of tomato seeds and the physiological and biochemical indexes of the seedlings grown for 25 days were studied.,And analyzed the expression of stress response genes in tomato by q RT-PCR technology.The research obtained the following experimental results:1.The effect of high gravity treatment on the gene expression profile of Arabidopsis seedlings:The Arabidopsis thaliana Col-0 seedlings grown for 5 d were treated with 1000×g of hypergravity,and transcriptome analysis was performed.There were 1,263 up-regulated genes and 1,028 down-regulated genes.These differentially expressed genes are annotated into 42 functional groups of GO functions,and their components are mainly concentrated in metabolic processes and cellular processes.Hypergravity treatment significantly affected plant hormone response,stress response and the expression of antioxidant-related genes and the photochemical process,and changed the growth and development of plants.KEGG enrichment analysis found that 452 up-regulated genes were significantly enriched in 4pathways,and 407 down-regulated genes were significantly enriched in 10 pathways.2.The effect of hypergravity treatment on the distribution of auxin in the root tip of Arabidopsis seedlings :After hypergravity treatment,the expressions of DR5:GUS,DR5:GFP,PIN1:GFP and PIN2:GFP all increased compared with the control within 30 minutes of slow seedling,but there was no significant difference in the expression of AUXI::YFP;after 2 h of slow seedling The expression of DR5: GUS and DR5: GFP was higher than that of the control,and there was no significant difference in the expression after 2 h compared with the control.These results indicate that hypergravity treatment increases the abundance of auxin transport proteins PIN1 and PIN2,which in turn increases the level of auxin in the root tip.3.The effect of hypergravity on the germination rate of tomato seeds:The germination rate of 1000×g and 2000×g increased the most within 24 h after hypergravity treatment,but the germination rate of each treatment was lower than that of the control;only 1000×g treatment germinated during the 24-48 h after hypergravity treatment The rate is higher than that of the control group;all treatment groups are still lower than the control group after the end of germination.The overall trend shows that hypergravity has a certain inhibitory effect on the germination of tomato seeds.4.The effect of hypergravity treatment on the fresh weight and physiological index content of seedlings:After hypergravity treatment,the fresh weight of the shoots of 25 d seedlings was increased,and the fresh weight was the highest under 4000×g treatment.The content of malondialdehyde(MDA)in the 25 d seedlings treatment group first decreased and then increased with the increase of centrifugal force.Trend,the MDA content is the lowest under the condition of 2000×g treatment,and it shows a very significant trend compared with the control group.Soluble protein and soluble sugars showed a trend of first increasing and then decreasing.Among them,the soluble sugar content reached the maximum under the4000×g treatment;the soluble protein content was the highest under the 2000×g treatment and was significantly increased by 29.7% compared with the control group;Appropriate hypergravity treatment can increase the chlorophyll content of tomato leaves,and the amino acid content such as serine,glutamic acid,and proline.The hypergravity environment is an extreme physical environment.Tomatoes ensure normal growth and development by increasing the content of osmotic adjustment substances in the body.5.The effect of high gravity treatment on seedling antioxidant enzyme activity:The activity of superoxide dismutase(SOD)showed a gradual upward trend with the increase of hypergravity,and the enzyme activity in the treatment group was significantly higher than that in the control group,and the enzyme activity in the 8000×g treatment reached the maximum.The activity of peroxidase(POD)and catalase(CAT)increased first and then decreased,and the peroxidase activity was highest at 2000 × g.In summary,high gravity treatment can improve the scavenging ability of active oxygen in 25-day seedlings,and enhance their adaptability to the environment stimulated by gravity.6.The effect of high gravity treatment on the expression of stress response genes in seedlings:High-gravity treatment has varying degrees of influence on the expression of five stress response genes including Sl MCP2 f,Sl DEAD31,SIMAPK6,SIETR6 and ASR1.Among them,high-gravity treatment inhibited the expression of two negative-regulated plant stress resistance genes,Sl MCP2 f and SIMAPK6,and induced the expression of three positive-regulated genes,SIETR6,Sl DEAD31 and ASR1.The above research results provide a theoretical basis for further exploration of the physiological and molecular mechanisms of hypergravity treatment affecting plant growth and development,and also provide technical support for the application of hypergravity treatment in agricultural production. |
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