NU 70/22-1

Plant pattern recognition receptors - TIR domain signaling and physiological roles

01/11/2026 to 31/10/2028

In plant immunity, pattern recognition receptors (PRRs) are crucial for detecting microbial signatures and initiating defense responses. In Arabidopsis, PRRs such as FLS2, EFR, XPS1, RLP32, LYM1/LYM3, and LORE recognize various surface structures of pathogens like Pseudomonas syringae pv. tomato. This recognition triggers pattern-triggered immunity (PTI), a defense mechanism that primes the plant for a more robust immune response. However, it remains unclear how each of these PRRs contributes to defense against specific proteobacterial pathogens and whether they function in a redundant, additive, or synergistic manner to activate PTI and limit the spread of adapted pathogens. Research described under Objective 1 focuses on understanding the roles of individual PRRs in basal immunity to bacterial infections in Arabidopsis.
Recent research emphasizes the crucial roles of EDS1 and PAD4 in activating PTI, with the binding of p-Rib-AMP/ADP to EDS1-PAD4 complexes being vital for this process. This activation is mediated by TIR domain-containing proteins that exhibit plant NADase activity. While the TNL protein SADR1 is known to be involved in late PTI response activation, our recent work suggests that this protein does not contribute to early PTI activation. This suggests that another TIR domain protein likely produces p-Rib-AMP/ADP, which is required for initiating early PTI through EDS1-PAD4 or EDS1-PAD4-ADR1 complexes. Research described under Objective 2 focuses on identifying and functionally chaaracterizing the specific TIR domain protein responsible for triggering early PTI responses.