Plant NLRs get by with a little help from their friends.

Many plant NLR (nucleotide-binding, leucine-rich repeat) immune receptors require other NLRs for their function. In pairs of chromosomally adjacent sensor/helper NLRs, the sensor typically carries an integrated domain (ID) that mimics the authentic target of a pathogen effector. The RPW8-NLR clade supports the function of many diverse plant NLRs, particularly those with a TIR N-terminal domain, in concert with a family of EP-domain containing signalling partners. The NRC clade of NLRs are required for the function of many unlinked sensor NLRs in Solanaceous plants. We evaluate recent advances in paired NLR biology in the context of the structure and possible mechanisms of the first defined plant inflammasome containing ZAR1.

Retracted: "CITRX thioredoxin interacts with the tomato Cf-9 resistance protein and negatively regulates defence".

The authors regret to announce they would like to withdraw this paper, for two main reasons: Since the paper was published, it has become clear that the thioredoxin that interacts in yeast 2-hybrid with the Cf-9 C-terminus is in fact localized in the chloroplast, rendering a role in Cf-9 signalling unlikely. Close scrutiny of the figures suggests several duplications. - In Fig 3A, the Anti-MBP band in lane 4 closely resembles the antiMBP band in Fig 3B lane 1, though slightly rotated. - In Fig 6A, the leaf disc in the panel labelled TRV:00, -Avr9, 30 min looks identical to the leaf disc in Fig S5, panel labelled Cf2 TRV:CITRX, -Avr2, 1 h. - In Fig 6C, multiple bands appear duplicated. For example, GlucA, TRV:00, -Avr9, 0 h duplicated with 6 h; and GlucB, TRV:00, +Avr9, 0 h duplicated with Hin1, TRV:00, +Avr9, 0 h. Source data for these figures are not available. All the authors agree that this paper should be withdrawn from the scientific literature.

Direct regulation of the NADPH oxidase RBOHD by the PRR-associated kinase BIK1 during plant immunity.

The rapid production of reactive oxygen species (ROS) burst is a conserved signaling output in immunity across kingdoms. In plants, perception of pathogen-associated molecular patterns (PAMPs) by surface-localized pattern recognition receptors (PRRs) activates the NADPH oxidase RBOHD by hitherto unknown mechanisms. Here, we show that RBOHD exists in complex with the receptor kinases EFR and FLS2, which are the PRRs for bacterial EF-Tu and flagellin, respectively. The plasma-membrane-associated kinase BIK1, which is a direct substrate of the PRR complex, directly interacts with and phosphorylates RBOHD upon PAMP perception. BIK1 phosphorylates different residues than calcium-dependent protein kinases, and both PAMP-induced BIK1 activation and BIK1-mediated phosphorylation of RBOHD are calcium independent. Importantly, phosphorylation of these residues is critical for the PAMP-induced ROS burst and antibacterial immunity. Our study reveals a rapid regulatory mechanism of a plant RBOH, which occurs in parallel with and is essential for its paradigmatic calcium-based regulation.