Physiological And Biochemical Characteristics Of Selenium-enriched Cowpea And The Response Of ABC Transporter Genes To Selenium

Cowpea（Vigna unguiculata（Linn.）Walp.）is one of the important conventional vegetable species in my country with a wide range of cultivation.Cowpea pods contain a lot of protein,carbohydrates and dietary fiber,as well as nutrients such as carotene,vitamin B and vitamin C,and have high edible and health care value.Elemental selenium is extremely important to human health,and increasing the selenium content of crops through selenium fortification to increase the dietary selenium intake of residents is one of the research hotspots in recent years.In-depth analysis of plant selenium physiological,biochemical and molecular response characteristics has important theoretical and practical significance for elucidating the mechanism of plant selenium accumulation,improving selenium-enriched cultivation measures,and cultivating selenium-enriched varieties.In this experiment,two long cowpea cultivars with different growth habit—youjia cowpea and dwarf cowpea were used as test materials,and sodium selenite（Na₂SeO₃）and nano-selenium（SeNPs）were used as selenium sources to study different forms of exogenous selenium.,The effects of different application concentrations,different harvest times and times of selenium application on selenium form,selenium content,nutritional quality and antioxidant capacity in pods.To provide a theoretical reference for clarifying the selenium enrichment and transport characteristics of cowpea and producing safe and reliable selenium-enriched cowpea.ABC transporters（ATP-Binding Cassette transporters）are an ancient and large family of transmembrane proteins involved in a variety of basic physiological processes,such as nutrition,development,responses to biotic and abiotic stresses,and interactions with the environment.Based on the previous RNA-seq analysis results of soybean and cowpea,this experiment investigated the response of ABC transporter family member genes in soybean and cowpea to different exogenous selenium treatments.The role of selenium metabolism and transport in plants provides a reference.The main results are as follows:The study showed that SeNPs and Na₂SeO₃were used as selenium sources（concentrations were set as 0,0.1,0.5,1.0,2.5,and 3.0 mmol/L,respectively）for foliar spraying.The results showed that with the increase of the exogenous selenium concentration,the accumulated selenium content in the pods of the two cowpea varieties increased significantly,and the effect of Na₂SeO₃on the selenium content in the pods was more obvious at the same concentration.Different external selenium sources and different application amounts have great influence on the existence form and content of selenium accumulated in cowpea pods.The main form of selenium detected in cowpea pods treated with different concentrations of SeNPs and Na2SeO3was SeMet,followed by Me SeCys.With the increase of exogenous selenium concentration,the types of selenium compounds detected in the pods also gradually increased,but all of them were mainly organic selenium（especially SeMet）,and inorganic selenium forms could only be detected in the high-concentration treatment group.In this experiment,the changes of physiological indexes and antioxidant enzyme activities of cowpea pods under different concentrations of exogenous selenium were detected.The results showed that the soluble protein and cellulose in the pods of the two cowpea varieties were increased after exogenous selenium treatment compared with the control;especially,the SeNPs treatment had a significant effect on the content of soluble protein and cellulose in dwarf cowpea.After the selenium treatment,the content of hydrogen peroxide in the pods of cowpeas was significantly reduced;at the same time,the activity of peroxidase in the pods of dwarf cowpeas could be effectively improved,and the activity of SOD enzymes could be effectively maintained.Differential expression analysis of the transcriptome data of soybean and cowpea showed that there were 40 and 150 differentially expressed ABC transporter genes in soybean and cowpea after selenium treatment,of which ABCB,ABCC,and ABCG subfamilies accounted for the majority.It indicated that the three subfamilies ABCB,ABCC and ABCG were the main force of the ABC transporter family to cope with selenium stress in legumes.The q-PCR experiment was performed on the selected soybean ABC transporter gene,and the experimental results were highly similar to the transcriptome data,which indicated that the ABC transporter played an important role in the accumulation of selenium in legumes.This study confirmed the feasibility of using nano-selenium and sodium selenite to produce selenium-enriched cowpeas to meet the selenium required by the human body,and provided a foundation for the field production of selenium-enriched cowpeas.The accumulation of selenium in plants provides a new idea,which is conducive to further research in the later stage,and provides a theoretical basis for scientific selenium supplementation.