Plant immune signaling network mediated by helper NLRs

Plant nucleotide-binding leucine-rich repeat receptors (NLRs) are intracellular immune receptors for pathogen recognition and signaling. They include sensor NLRs (sNLRs) that detect pathogens, and helper NLRs, which transduce downstream immune signals. During immune responses, both membrane -localized pattern recognition receptors (PRRs) and sNLRs rely on helper NLRs for signal transduction. The Arabidopsis helper NLRs, ADR1s and NRG1s, along with their interacting lipase-like protein dimers, are differentially required by sNLRs. Recent structural and biochemical analyses suggest that they assemble into oligomeric resistosomes with lipase -like protein dimers upon perception of small molecules pro-duced from enzymatic activities of upstream TIR-type sNLRs. As a result, ADR1s and NRG1s form membrane calcium channels to induce immune responses and cell death. In contrast, Solanaceous NRC clade helper NLRs transduce signals from many sNLRs and some PRRs. Here, we sum-marize the recent advances in plant helper NLR research, with a focus on their structural and biochemical mechanisms in immune signaling.

Automated summary

Plant NLRs are important immune receptors for pathogen recognition and signal transduction. Helper NLRs are required by both membrane-localized PRRs and sNLRs for immune signaling. Recent studies have revealed the structural and biochemical mechanisms of helper NLRs in immune signaling, such as the formation of oligomeric resistosomes and membrane calcium channels. The research on plant helper NLRs provides valuable insights into the immune response mechanisms in plants.