| In China,the potato has become the fourth largest food crop after rice,corn,and wheat.In recent years,the frequent occurrence of extreme drought events in China has seriously affected the normal growth and development of potatoes,leading to a significant reduction in the quality and yield of potatoes.Therefore,exploring the molecular mechanism of the effect of drought stress on potato starch synthesis will help to solve the problem of potato drought resistance and survival adaptability.In this study,the main potato varieties in Yunnan,Cooperation 88,Qing Shu No.9,and Li Shu No.6,were used as the experimental materials.The osmotic simulation water stress method was used during the seedling stage(15 ± 2 cm)and tuber expansion stage(about 20 days after flowering)of potatoes.Different concentrations of PEG were used to simulate different degrees of drought conditions,to explore the changes in potato growth and physiological and biochemical characteristics under different degrees of drought conditions the activity of key enzymes in starch synthesis and the changes in starch accumulation,as well as the changes in yield composition,were further analyzed using transcriptome sequencing technology to analyze differentially expressed genes under drought stress at the transcriptional level.Bioinformatics methods were used to classify and annotate differentially expressed genes and analyze enriched metabolic pathways,thereby exploring the impact of drought stress on the mechanism of starch synthesis.The results showed that:1.Drought stress hinders the growth and development of potatoes;Moreover,with the increase of drought degree,the plant will suffer more damage.To alleviate the damage caused by drought,the stem diameter of potatoes increased under a certain degree of drought stress.2.In different varieties of potatoes,the response of physiological and biochemical indicators to drought stress has different change rules at different levels.At the level of antioxidant enzyme system,Cooperation 88 and Li Shu No.6 can more effectively remove the oxygen-free radical protective membrane system;At the level of osmoregulation substances,Qing Shu No.9 was in moderate drought,and Cooperation88 and Li Shu No.6 were in severe drought,which had the most protective effect on the water retention capacity,living substances and biofilm of cells;At the level of osmotic stress substances,Li Shu No.6 has a strong resistance to drought,while Qing Shu No.9has a low ability to produce biomacromolecule damaging substances and cell toxicity under drought stress.These differences in response to drought stress are caused by interspecific differences.3.Under drought stress,the content of total starch,amylose,and amylopectin in potato tubers decreased.However,Qing Shu No.9 and Li Shu No.6 had peak amylopectin content under moderate and severe drought conditions,indicating that the drought conditions had a certain promotion effect on the production of amylopectin.4.Correlation analysis showed that under drought stress,AGPase and GBSS played an important role in the synthesis of starch components of Cooperation 88,and AGPase,GBSS,and SBE played an important role in the synthesis of starch components of Qing Shu No.9.AGPase,GBSS,SBE,and SSS all participated in the synthesis of starch components of Li Shu No.6.5.The analysis of yield composition shows that there are differences in the effects of different degrees of drought stress on the yield composition of potato varieties,with severe drought stress having the greatest impact on the yield composition of potatoes.6.Transcriptomic analysis showed that,under different degrees of drought stress,the expression of 10 genes in potato starch and sucrose metabolism pathway is different.SPS2,SS2,and AMY3 play a role in glycogen biosynthesis module to regulate starch synthesis and decomposition respectively;TPPJ,INVA,and TPS11 regulate sucrose decomposition;At4g39010,BGLU12,and BACOVA＿02659 regulate glucose synthesis;SS regulates the starch synthesis and sucrose decomposition.And a certain degree of water stress is conducive to the distribution of photosynthetic products into tubers;Moreover,with the increase of drought degree,the starch in potato tubers is degraded into sucrose and glucose with smaller molecular weight,and the trehalose content is also significantly increased.In summary,the results showed that under different degrees of drought,the total starch,amylose,and amylopectin content of potato tubers showed a downward trend.The key enzymes for starch synthesis comprehensively acted on the production of starch components,and severe drought stress had the greatest impact on the yield composition of potatoes.Among the starch and sucrose metabolic pathways,10 genes were involved in starch synthesis and decomposition,sucrose decomposition,and glucose synthesis,respectively,playing a key role,this study provides a theoretical basis for further research on potato drought resistance cultivation by degrading starch in potato tubers into sucrose and glucose with lower molecular weight. |
