PthA4AT, a small TAL effector from Xanthomonas citri subsp. citri induces immunity in Nicotiana benthamiana.

ROESCHLIN R.A.; GARCIA L.; BOCH J.; UVIEDO F.; MOLINA M.C.; GADEA J.; CHUÁN A.; MARTINEZ M.F.,; MARANO M.R.

Belgrado

Conferencia; 4th Annual Conference of the EuroXanth COST Action "Integrating Science on Xanthomonadaceae for integrated plant disease management in Europe"; 2021

COST Action CA16107 EuroXanth

Transcription-activator-like effectors (TALE) are secreted by Xanthomonas, acting as eukaryotic transcription factors that can target both susceptibility or resistant genes in the plant cells. They recognize specific DNA sequences in the host promoters through a domain consisting of a variable number of ~34 amino acid repeats following a well characterised code. The main virulence factor of Xanthomonas citri subsp. citri (X. citri), the bacteria causing citrus canker, is PthA4, a 17.5-repeats TAL effector activating susceptibility genes in Citrus. Recently, a natural variant of X. citri triggering a hypersensitive response (HR) in C. limon and C. sinensis was isolated, and the effector triggering this HR was shown to be a 7.5- repeat PthA4-derivative TALE (PthA4AT), likely activating a resistance gene on these citrus hosts. Interestingly, PthA4AT also causes HR in the non-host plant Nicotiana benthamiana. In this study, we have characterised the defense response leading to the HR deployed by Nicotiana when challenged with this effector. Moreover, we show how this defense response prevents Nicotiana from further infections by virus and bacteria, raising the posibility to use it as a biological control. Finally, artificial TALE effector technology combined with transcriptomic data has allowed us to refine PthA4AT targets in the plant cell as an initial step towards the identification of the Nicotiana resistence gene responsible for this HR.