| The absorption of exogenous selenate by plants is affected by the external sulfate environment.And the interaction between sulfate and selenate will also affect plant growth and accumulation of trace elements.Studies have shown that the absorption of selenate in plants depends on sulfate transfer protein(SULTR).Therefore,when the external sulfate environment changes,screening the optimal sodium selenium concentration to promote wheat growth,nutrient element absorption and accumulation and understanding the related transporter genes have certain significance for the study of selenium-rich wheat.In this experiment,two wheat varieties were selected,based on the basic nutrient solution culture,whether or not sulfate was combined with different concentrations of sodium selenate were used to study the effects on the growth and development of wheat seedlings and the content of trace elements.And sereened the optimal sodium selenium concentration to promote the growth of wheat seedlings.Transcriptome sequencing and fluorescence Quantitative PCR were used to study the expression of differential genes in roots and leaves under different treatments.The main results obtained are as follows:(1)In different nutrient solutions,low-concentration sodium selenate could promote the growth of wheat seedlings and increased the content of various beneficial elements such as iron,copper,zinc,selenium,and molybdenum in plants.The optimum sodium selenate concentration for promoting wheat growth under sulfate-deficiency nutrient solution(-S)and normal nutrient solution(+S)were 1 and 5 μmol·L-1,respectively.At this time,the wheat seedling height,root length,chlorophyll content,and selenium tolerance index were greater,the accumulation of elements such as iron,copper,zinc,selenium,and molybdenum were also greater.(2)Selenium and molybdenum were more mobile and could be transported from the roots to the ground,mainly concentrated in the ground.The migration capacity of iron,copper and zinc in the plant were poor,mainly due to accumulation in the roots.Sulfate deficiency treatment could promote the accumulation of selenium and molybdenum in roots,stems and leaves of wheat seedlings,and the difference was significant or even extremely significant with the increased of sodium selenium concentration.It showed that both sodium selenate and molybdate competed with sulfate.Sulfate deficiency and sodium selenate treatment would reduce the iron,copper and zinc content in the root,but high concentration of sodium selenate caould increase the iron,copper and zinc content in the root to make it close to the control treatment.The appropriate concentration of sodium selenate could increase the content of iron,copper and zinc in leaves.In different nutrient solutions,with the increased of sodium selenate concentration,the selenium content of wheat leaves also increased.Under sulfate deficiency treatment,the selenium content in wheat leaves was the highest when the sodium selenate concentration was 10 μmol·L-1.At this time,both wheat varieties showed symptoms of poisoning,the leaves began to turn yellow,and the chlorophyll content,root length and the selenium tolerance index were the lowest,and sulfate could reduce the selenium toxicity to wheat seedlings to some extent.(3)Transcriptome sequencing was performed on the roots and leaves of Donghei 1 treated with normal nutrient solution combined with 0 and 10 μmol·L-1 sodium selenite.The differential genes were mainly concentrated in KEGG pathways such as phenylpropane biosynthesis,starch and sucrose metabolism,and plant hormone signal transduction.These genes were enriched in 27 GO functions.9 differential SULTR genes were screened out and distributed in 4 SULTR gene subfamilies.COG were classified as inorganic ion transport and metabolism.After bioinformatics analysis,it was found that except for the physical and chemical properties of Tae Sultr3.5,the remaining SULTRs were stable alkaline fat-soluble hydrophobin proteins.Six differential SULTR genes were selected to determine their expression levels in different parts under different treatments.(4)The absorption of sodium selenate by plant roots is through a high-affinity sulfate transporter.Under different nutrient solutions,the expression levels of root genes in both varieties were higher than those in leaves treated with the same concentration of sodium selenate.The absorption of exogenous sodium selenate from the roots of wheat seedlings depended on the high expression of Tae Sultr 1.3 and Tae Sultr 2.1.Tae Sultr 1.1 and Tae Sultr 1.3 played an important role in the selenium accumulation process in wheat seedling leaves,and the gene expression had nothing to do with sulfate nutrition status.After treatment with different concentrations of sodium selenate,Tae Sultr 1.1,Tae Sultr 1.3,Tae Sultr 2.1,and Tae Sultr 3.3 were more prominently expressed in the roots of nutrient solution with sufficient sulfate.Tae Sultr 1.1,Tae Sultr 1.3,and Tae Sultr 2.1 were highly expressed in roots treated with sulfur-deficient nutrient solution.(5)The expression of 6 SULTR in leaves were induced by sulfate and induced by sulfur deficiency in roots.When sulfate is sufficient,sodium selenate could inhibit gene expression in leaves and promoted gene expression in roots,thereby promoted the absorption of sodium selenate in the roots,simultaneously,it protected the growth and development of wheat seedlings and did not cause excessive selenium to damage plants. |
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