| Sugarcane(Saccharum officinarum)is the main sugar crop in China,widely cultivated in the south of China,of which sugarcane streak mosaic virus(SCSMV)is one of the main pathogens of sugarcane virus disease,and the P1 protein encoded by SCSMV plays an important role in the pathogenesis process,but its molecular mechanism involved in the interaction between viruses and plants is still relatively unknown.In this experiment,differential accumulation proteins(DAPs)in the heterologous expression of P1SCSMV were identified using a newly developed 4D proteomic method using a potato virus X(PVX)-based expression system.qRT-RCR and Western blot analysis were used to assess the credibility and reliability of the data.Then,four candidate proteins were functionally studied by a TRV-based gene silencing system,including two highly upregulated proteins(NbEAS and NbECA)and two significantly downregulated proteins(NbASP and NbXTH1).It was found that silencing NbXTHl gene plants exhibited symptoms of leaf fold curling,indicating that NbXTH1 was closely related to P1SCSMV.Furthermore,it was further determined that the expression level of NbXTH1 was inhibited by P1SCSMV in both transgenic P1SCSMV and sugarcane infected with SCSMV.In order to clarify how P1SCSMV inhibits the relative expression of NbXTH1 in Nicotiana benthamiana,it was verified whether the transcription factor NbBES1,which directly acts on the upstream of NbXTHl,interacts with P1SCSMV.It was found that P1SCSMV interacted directly with the transcription factor NbBESl both in vivo and in vitro.This interaction inhibits the binding of NbBES1 to the E-box element of the NbXTH1 promoter region and interferes with the normal transcription of NbXTH1 in plants.XTH gene has spatiotemporal expression specificity and is involved in a variety of biological functions such as plant cell wall remodeling,plant growth and development,and response to adversity.Based on this,the disease resistance of NbXTH1 protein was further explored.The broad-spectrum disease resistance of NbXTH1 gene was identified by transient expression of NbXTH1 gene,TRV silencing NbXTHl gene and transgenic super-expression NbXTH1 Nicotiana benthamiana plant by inoculation of viruses and fungi,and the results showed that the presence of NbXTHl protein improved the resistance of NbXTH1 to plant viruses and fungi,that is,NbXTH1 protein has a certain broad-spectrum disease resistance.XTH can catalyze the hydrolysis and synthesis of Xyloglucan molecules and participate in the degradation of xylan.Xyloglucan and xylan are the main components of hemicellulose,and the cell wall is a network structure composed of cellulose,hemicellulose,glycosylated proteins and lignin,and plays a protective and supporting role in cells,which can resist the invasion of external pathogenic bacteria.Therefore,in order to further explore the disease resistance mechanism of NbXTH1 gene,the contents of xylogcan and xylan in the cell wall of sugarcane infected with transgenic P1SCSMV Nicotiana benthamiana and SCSMV were detected,and it was found that the content of xyloglucan decreased and the content of xylan increased.At the same time,transmission electron microscopy found that the cell wall width of the transgenic NbXTHl Nicotiana benthamiana plant was thicker than that of the non-transgenic plant.Spraying NbXTH1 substrate small molecule xyloglucan solution also confirmed that xyloglucan affected the disease resistance of plants.In summary,the results show that NbXTH1 changes the ultrastructure of cell wall by disrupting the content distribution of xyloglucan and xylan in the cell wall,which plays a role in resisting the invasion of plant viruses and fungi.The results revealed the molecular mechanism of plant cell wall-mediated pathogen resistance and identified NbXTH1 as a broad-spectrum plant viral and fungal resistance protein.In this study,based on the pathogenic factor function of P1 protein encoded by SCSMV,the differentially expressed protein NbXTHl was identified by 4D proteomic screening,and it was found that the direct interaction of P1SCSMV with the transcription factor NbBES1 inhibited the binding of NbBES1 to the E-box element of the NbXTH1 promoter region,and interfered with the normal transcription of NbXTH1.It was verified that NbXTH1 exerts broad-spectrum disease resistance by controlling cell wall structure by regulating the content of xyloglucan and xylan.It provides direct evidence for the participation of NbXTHl in biological stress,and also provides a basis for the application of small molecule xyloglucan and broad-spectrum disease resistance gene XTH in crop breeding. |
