Functional Analysis Of Verticillium Dahliae Spt-Ada-Gcn5 Acetyltransferase Complex Subunit Ada1

Verticillium dahliae is a soil-borne pathogen that causes verticillium wilt in various dicots and attacks a variety of economically important forest trees and crops.At present,the research on the pathogenic mechanism of V.dahliae mainly focuses on three aspects: transcriptional regulation,secreted proteins and microsclerotia.However,the control of V.dahliae is difficult due to its complex pathogenic mechanism,the resistance of microsclerotia to stresses and the lack of genetic resistance in many plant hosts.SAGA(Spt-Ada-Gcn5 acetyltransferase complex)is an ATP-independent multifunctional transcription coactivator complex that loosens chromatin structure by acetylating lysines of histone,thereby promoting the initiation of gene transcription.SAGA complex has been extensively studied in yeast,but its role in the process of pathogens infecting host plants is rarely reported.The purpose of this study was to identify SAGA in V.dahliae and to understand the regulatory network and pathogenic mechanism of VdAda1 subunit.In this study,18 SAGA complex members in V.dahliae were firstly identified by Blastp using protein sequences of the known Saccharomyces cerevisiae and Fusarium fujikuroi SAGA complex as queries,and by RT-qPCR,it was found that the expression of most of them were significantly induced during the infection of cotton by V.dahliae.Considering the important role of Ada1 subunit on SAGA complex,this study took VdAda1 as the main research object to preliminarily explore the function of V.dahliae SAGA complex.After obtaining the VdAda1 deletion mutants and complemented transformants by Agrobacterium tumefaciens-mediated transformation(ATMT)method,the essential role of VdAda1 in vegetative growth,conidia production,melanin and microsclerotia formation and pathogenicity of V.dahliae was illustrated by the observation of growth phenotype,quantification of conidiation,pathogenicity assay and so on.RT-qPCR results indicated that the loss of VdAda1 led to an imbalance in the expression of other SAGA members;The western blot analyses further demonstrated that the histone H3 acetylation function performed by the HAT module was severely affected after VdAda1 deletion.Comparative transcriptomic analysis revealed that the deletion of VdAda1 resulted in alteration of the transcription level of 3661 genes in V.dahliae,including genes encoding transcription factors and secreted proteins,suggesting its prominent role in regulating the transcriptional level and virulence.In addition,a pathogenicity-related gene regulated by VdAda1 and two secreted proteins inhibiting plant immune responses were identified respectively by pathogenicity assays and agro-mediated transient expression on tobacco leaves,further revealing the global regulatory function of VdAda1.In conclusion,this study identified the composition of SAGA complex in V.dahliae for the first time and demonstrated that the VdAda1 subunit modulates multiple physiological processes by regulating the expression of key functional genes,thereby affecting virulence of V.dahliae.The important function of VdAda1 may provide a new target for the control of V.dahliae.