Physiological Changes And Transcriptome Analysis Of Barley In Response To Barley Yellow Dwarf Virus (BYDV) Infection

As one of the four main cereal crops,barley has the characteristics of wide growth range and strong stress resistance,and has been widely planted all over the world.Barley yellow dwarf virus(BYDV)is a virus transmitted specifically by aphids and then infecting cereal crops.The common symptoms are yellow leaves and dwarf plants.In serious cases,it will reduce the quality of crops or even reduce production.Therefore,it is very important to study the physiological response and gene expression difference of barley under virus infection,and further explore the physiological and molecular mechanism of barley response to virus stress.In this paper,Atlas and Atlas68 barley were used as materials,combined with indoor hydroponic experiment,and the methods of conventional physical and chemical analysis,ultra-thin section technology,high-throughput sequencing and real time fluorescence quantitative PCR were used to study.The ultrastructural characteristics of barley leaves under barley yellow dwarf virus stress,the physiological response characteristics of photosynthesis and stress resistance,and the response of leaves to virus stress at the transcriptional level were studied.The main results are as follows:(1)Barley yellow dwarf virus stress led to changes in barley apparent morphology and stress resistance physiological indexes in leaves.Plant dwarfing and leaf yellowing occurred in both barley under virus stress,but the symptoms of Atlas68 were lighter than Atlas.The activities of superoxide dismutase and phenylalanine ammonia-lyase in the leaves of the two kinds of barley increased with the extension of stress time,and the peroxidase activity increased first and then decreased,and the enzyme activity in the leaves of Atlas68 was generally higher than that of Atlas,indicating that barley yellow dwarf virus stress activated the antioxidant defense system in barley,and improve stress resistance by regulating the activity of disease related enzymes.In addition,the contents of soluble sugar,proline and malondialdehyde in the leaves of the two kinds of barley increased gradually with the increase of virus stress time,and the contents in the leaves of Atlas68 barley were generally higher than Atlas,indicating that barley yellow dwarf virus stress induced the synthesis of permeability regulators in barley.The antioxidant capacity and osmotic regulation capacity of Atlas68 under virus stress are generally stronger than Atlas.(2)Barley yellow dwarf virus stress affected the ultrastructure of chloroplasts in barley leaves and led to changes in photosynthetic physiological indexes.After virus stress,the chloroplast internal structure of the two kinds of barley was seriously damaged,and even the chloroplast membrane was damaged and the contents flowed out,resulting in the decrease of chlorophyll content and the decrease of light energy capture ability of barley.With the extension of stress time,the net photosynthetic rate and maximum photochemical efficiency decreased significantly,indicating that the photosynthetic mechanism in barley was damaged and the photochemical reaction was inhibited,which seriously affected the photosynthetic capacity of barley.The chlorophyll content,gas exchange parameters and chlorophyll fluorescence parameters of barley leaves inoculated with toxic aphids in Atlas68 were generally higher than those in Atlas,indicating that the inhibition of photosynthetic capacity of Atlas was more serious than that of Atlas68 after virus stress.(3)Barley yellow dwarf virus stress caused gene differential expression in two kinds of barley.By comparing the differences of gene expression levels between the two kinds of barley under virus stress,a total of 3575 differentially expressed genes related to resistance were identified,which were mainly concentrated in the pathways related to plant resistance,such as plant pathogen interaction pathway,antioxidant defense mechanism and plant hormone signal transduction pathway.Subsequently,five plant pathogen interaction related genes,five plant hormone signal transduction related genes and four candidate genes related to antioxidant defense mechanism were screened and identified.The results showed that barley yellow dwarf virus stress could induce the formation of complex resistance pathways and gene regulatory networks,and activate the defense response dominated by antioxidant defense mechanism.In summary,this paper investigated the response mechanism of barley to BYDV stress from the aspects of morphology,physiology and transcriptome.The results showed that BYDV stress activated the antioxidant defense system in barley,induced the synthesis of malondialdehyde and osmotic regulators,and improved stress resistance by regulating the activities of disease-related enzymes.In addition,BYDV stress also destroyed the chloroplast structure of barley,resulting in the inhibition of photochemical reactions and affecting the photosynthetic capacity.In addition,BYDV stress can induce the formation of complex resistance pathways and gene regulatory networks,and activate defense responses dominated by antioxidant defense mechanisms.The results provide a theoretical basis for further research on the physiological and molecular mechanisms of barley response to barley yellow dwarf virus infection.