Molecular Mechanisms Underlying Dwarf Symptom Formation Involved In The Gibberellin Pathway In Wheat After Infection Of Barley Yellow Dwarf Virus GAV

Wheat yellow dwarf is a worldwide disease caused by barley yellow dwarf viruses?BYDVs?in cereal crops,especially in the wheat growing areas of northern China.After infection with BYDVs in the field,the wheat shows typical symptoms such as leaf yellowing with an inverted V shape,plant dwarfism,and reduced tillering.Among them,BYDV-GAV is the most popular species found in China,but its underlying pathogenic mechanism is not yet clear.Therefore,we need to explore the interaction between BYDV-GAV and the hosts to reveal the molecular mechanism of virus pathogenicity,which has important theoretical guiding significance for controlling wheat yellow dwarf disease.Brachypodium distachyon?Brachypodium?,as model plant for gramineae,has many advantages compared with wheat,such as dwarf phenotype,simple genome,easy cultivation and mature genetic transformation system.Gibberellins?GAs?are important phytohormones that are essential for plant growth and development in higher plants.The decrease or absence of the gibberellin content often leads to plant dwarfing.Because of plant dwarfism is one of the typical symptoms caused by BYDV-GAV infection,this article uses gibberellin as an entry point to preliminary explore the formation mechanism of plant dwarfing in BYDV-GAV infected Brachypodium.The main research contents are as follows:?1?At the two-leaf one-heart stage,Brachypodium Bd21 were inoculated with viruliferous aphids carrying BYDV-GAV.At 21 days post inoculation,Brachypodium showed typical symptoms such as leaf redness and plant dwarfing.Liquid chromatography was used to determined the content of GA_3.The results indicated that infection of BYDV-GAV in Brachypodium along with a decrease in the content of active GA₃.Then RT-q PCR was used to synthesize the expression level of GA key syntheses Bd KO,GA signal transduction pathway receptor Bd GID1 and the positive regulator Bd GID2 and the results showed that they all significantly down-regulated.Whereas the relative expression level of the GA inactivation enzyme Bd GA2ox and the gibberellin signal transduction pathway inhibitor Bd DELLA-SLN were significantly up-regulated.In addition,appropriate concentration of exogenous GA can effectively relieve the dwarfing symptoms caused by virus infection.?2?The coding sequences of Bd KO?Bd GID1?Bd GID2 and Bd DELLA-SLN were amplified and constructed into yeast two-hybrid bait vector p GADT7.Subsequently,these constructs were co-transformed into yeast cells with prey plasmids p GBKT7-MP and p GBKT7-CP,respectively.The yeast two-hybrid results showed that MP protein interacted with Bd GID2 and Bd DELLA-SLN.The bimolecular fluorescence complementary?Bi FC?results further indicated that MP interact with Bd GID2 and Bd DELLA-SLN in the nucleus.?3?Bd DELLA-SLN deletion mutants AD-DELLA-SLN?DELLA and AD-DELLA-SL N?GRAS were constructed to confirm the interaction region by yeast two-hybrid assay.The results showed that the GRAS domain was the main interaction region between Bd DELLA-SLN and MP,which could inhibit the growth of plants.?4?BSMV-VIGS technology was performed to analysis the function of Bd GID2 and Bd DELLA-SLN.The results showed that Bd GID2 silenced Brachypodium plants represented obvious dwarf phenotype,while the height of Bd DELLA-SLN silenced Brachypodium plants were increased significantly.The results suggested that the gene expression levels of Bd GID2 and Bd DELLA-SLN were positively and negatively correlated with the height of Brachypodium plants,respectively.In summary,after BYDV-GAV infection in Brachypodium,the expression of some key factors of GA pathway were disturbed,which resulting in the weakened of GA effect and ultimately,causing the dwarf of Brachypodium plants.In addition,it is speculated that the protein MP interacts with Bd GID2 and Bd DELLA-SLN to regulate their expression positively and negatively,respectively,which may responsible for the formation of dwarf symptom in the BYDV-GAV infected plants.