Functional Analysis Of NbFLA34 And NbHRLI4 In Turnip Mosaic Virus Infection

Plant virus is a biological factor that seriously endangers the quality and safety of agricultural products,seriously affects the yield and quality of agricultural products,and causes huge economic losses.Potyvirus is the largest genus of plant viruses,and turnip mosaic virus(Tu MV)is one of the most serious in potyviruses.In the process of virus infection,some host genes regulate the host resistance to virus in different ways to inhibit virus infection.Understanding the role and mechanism of these resistance genes in the process of virus infection will help us understand the virus-plant interaction,and provide a theoretical basis for the research and regulation of plant disease resistance as well as the prevention and control of agricultural product.6K2 is a membrane protein of Tu MV which is vital for virus replication and movement.On the basis of yeast screening library of Tu MV 6K2 protein,we found that fasciculin like arabinogalactan(FLA)Niben101scf12431g00010.1 interacted with6K2,and was named Nb FLA34 by genome-wide identification.The Nb FLA family can be divided into four subclasses,each of which is relatively conservative in evolution,and most Nb FLAs are down regulated after Tu MV infection.Nb FLA34 belongs to subclass III,its GPI anchor site and Gxxx G motif in 6k2 are the key sites for their interaction.Tu MV infection significantly down regulated the transcription level of Nb FLA34.However,overexpression of Nb FLA34 inhibited the accumulation of Tu MV and GPI was responsible for the inhibition.Nb FLA34 depends on Gxxx G motif for the interaction between 6K2,which is also a key site for 6k2 self interaction.Further studies showed that Nb FLA34 could interfere with 6K2 self interaction,thus inhibiting 6K2 induced vesicle aggregation and plasmodesmata targeting.In conclusion,this study revealed that Nb FLA34 could influence the function of virus vesicles by interfering with 6K2 self interaction,thus endowing the host with resistance to Tu MV.At the same time,we screened Nb HRLI4 by transcriptome sequencing,a member of HR-like lesion inducing(HRLI)gene,which is down regulated by Tu MV.Silencing Nb HRLI4 promoted virus infection and down regulated the expression of SA pathway genes.Exogenous application of SA could reduce the susceptibility of Nb HRLI4 silencing.Transient expression of Nb HRLI4 could inhibit the accumulation of virus and up-regulate the expression of SA pathway genes.Transient expression of Nb HRLI4 alone could induce HR-like cell death,but the degree of cell death in Nah G transgenic plants is reduced,suggesting Nb HRLI4 may induce cell death in a SA dependent manner.In addition,we also found that Nb HRLI4 interacted with Tu MV-P3,which may have been up-regulated by P3 in the early stage of infection,suggesting that Nb HRLI4 may induce plant resistance by recognizing P3.In conclusion,this study revealed that Nb HRLI4 can induce cell death through SA pathway,thus regulating the host basic immune response.These studies are of great value for further understanding the host components involved in the process of plant virus resistance.