A Novel Transcription Factor of Regulating Ag-8 Biocontrol to Grapevine Crown Gall

Grapevine crown gall (GCG) is a major disease caused by the Allorhizobium vitis that causes significant losses in the grape industry. In this study, a strain of Agrobacterium tumefaciens (Ag-8) from soil was found to have a significant effect on grapevine crown gall. The present study was conducted to investigate the potential impact of the AraC family transcription factor ata (Agrobacterium tumefaciens AraC) on the biocontrol capacity of Ag-8 and to elucidate the potential mechanisms of its action. To this end, an ata deletion mutant (Δata) was constructed. It was found that the biofilm, motility, and colonization of the ata deletion mutant strain were significantly lower than those of the wild strain Ag-8. By analyzing the Δata transcriptome data, we focused our attention on the ABC transporter protein araH, and RT-qPCR showed that it was significantly down-regulated in the Δata strain. In a follow-up study, the candidate gene araH deletion strain (ΔaraH) was found to have significantly lower biofilm formation, motility, and biocontrol ability than the wild-type strain Ag-8. Therefore, araH may be implicated as a pivotal target gene of ata in modulating the biocontrol capability of Ag-8. This study supports developing biocontrol strategies targeting ata-regulated colonization in Agrobacterium to enhance the sustainable management of grapevine crown gall.