Transcriptional And Metabolic Changes In Wheat Developing Seeds Under Waterlogging Stress

Wheat(Triticum aestivum L.)is one of the main grains produced and consumed in the world and plays a vital role in global food security.Soil waterlogging has become one of the main environmental factors restricting wheat yield and seriously affects the growth and development of wheat.In this study,the wet-tolerant wheat variety Huamai8 and the non-wet-tolerant wheat variety Huamai 9 were used as experimental materials.On the day of flowering,wheat was treated with 0 and 5 days of waterlogging,and then returned to normal growth.6 DAA,9 DAA,12 DAA,15 DAA,18 DAA,24 DAA,30 DAA and Mature grains were selected(DAA: days after anthesis).After analyzing the phenotypic changes of wheat grains under waterlogging stress,the metabolic regulation of wheat grains in response to waterlogging stress was analyzed based on transcriptomics and metabolomics.The research results show that:1.Under short-term waterlogging stress(5 days),we observed the changes of grain phenotype.We found that the fresh weight of grain decreased significantly before 12 DAA,and the dry matter accumulated rapidly.In addition,waterlogging shortened the filling time of wheat,advanced the ripening time and accelerated the development process to adapt to the waterlogging environment.At the same time,waterlogging affected the grain filling rate of wheat(increased first and then decreased),and 12 DAA was an important dividing time node.The initial grain filling rate and peak grain filling rate of the two varieties were significantly different,indicating that the two varieties were different in the development process,and the influence of the grain filling rate had an effect on the development process.2.The changes of metabolites in wheat grains after waterlogging stress were studied by LC-MS metabolomics.The results showed that 482 known metabolites were detected after waterlogging stress,including 10 categories including lipids,flavonoids,vitamins,sugars,nucleotides and their derivatives,organic acids,amino acids and their derivatives,phentolamines and polyphenols,hormones and their derivatives.KEGG analysis showed that Huamai 8 involved 16 metabolic pathways,Huamai 9 involved21 metabolic pathways,and "diterpenoid biosynthesis" and "niacin and niacinamide metabolism" were significantly responsive in Huamai 8.In addition,"zeatin biosynthesis","indole alkaloid synthesis" and "linoleic acid metabolism" were mainly enriched in Humai 8.Metabolic pathways such as "arginine and proline metabolism","niacin and niacinamide metabolism","tryptophan metabolism" and "lysine degradation" were mainly enriched in Huamai 9.3.Transcriptomics was used to study the effect of gene expression on wheat grain after waterlogging stress.The results showed that more genes were involved in the regulation and up-regulation of waterlogging stress,indicating that wheat grain mainly responds to waterlogging through up-regulation of genes.By analyzing the differentially expressed genes of waterlogging,we found that plant hormone synthesis,ascorbate-glutathione cycle and glucose metabolism may play a key role in the waterlogging tolerance of winter wheat.We then integrated metabolome data to focus on plant hormones,ascorbate-glutathione cycles and glucose metabolic pathways.The results showed that the gene expression peak was advanced and the expression amount was increased by regulating the synthesis genes related to ethylene,ababolic acid and jasmonic acid under waterlogging stress,so that the wet-tolerant variety Huamai 8could better cope with waterlogging environment by accumulating more hormones before 12 DAA.The early development of wheat grain formed a complex regulatory network through antioxidant enzyme system and non-antioxidant enzyme system(phenolic acids and flavonoids,etc.),which jointly resisted external stress.Before 12 DAA,the wet-tolerant varieties significantly enhanced the TCA cycle by prolonging the gene expression time,while the wet-tolerant varieties advanced the gene expression peak time to better help the plant to recover growth after stress.The expression level of glycolysis and the late fermentation of glycolysis were significantly improved in the wet-tolerant varieties,which helped the plants recover quickly from the effects of stress.