NLRs guard metabolism to coordinate pattern- and effector-triggered immunity

Linking plant metabolism and immunity through methionine biosynthesis

“…In this tour de force, rice appears to have succeeded to counteract this fungal adaptation by expressing the intracellular NLR PigmR receptor, which binds PICI1 protein and yields a protective effect against the AvrPi9mediated PICI1 degradation. In summary, the findings by Zhai et al (2021) represent a case example on the inter-linkage and importance of primary metabolism (i.e., Met metabolism) for flexible immune adaptation of plants following pathogen attack.…”

“…This holds true, for example, in the case of lysine catabolism, which is required for the synthesis of pipecolic acid, a regulator of systemic acquired resistance (SAR) (Na ´varova ´et al, 2013), or the accumulation of some amino acids and their metabolic by-products that function as triggers of resistance (Zeier, 2013). In this same regard, a link between methionine metabolism and plant defense has recently been unveiled by Zhai et al (2021). Here, a novel deubiquitinase (named PICI1, which stands for pigmR-interacting and chitininduced protein 1) from rice was shown to be key in the promotion of disease resistance to Magnaporthe oryzae, the causal agent of blast disease.…”

“…ET is required for disease resistance to fungal pathogens, such as M. oryzae, and, consequently, the ethylene pathway is a common target for pathogens, who deliver effectors to hijack the route and bypass plant immunity (Washington et al, 2016;Zhao et al, 2017). In the paper by Zhai et al (2021) the authors demonstrate that METS1 targeting by PICI1 and its subsequent stabilization occurs during activation of both PTI (pattern-triggered immunity) and ETI (effector-triggered immunity) in response to the fungi.…”

“…During the evolutionary arms race between rice and M. oryza, the fungi seems to have evolved effectors to bind and degrade PICI1, counteracting the PICI1-METS1-ET immune cascade. In a screen, Zhai et al (2021) found seven fungal effectors (AvrPizt, AvrPii, AvrPia, AvrPWL2, AvrPi9, AvPikC and AvrPikD), which specifically bind to PICI1, although the seven effectors interacted with PICI1 in vitro pull-down assays, only three effectors (AvrPii, AvrPWL2, and AvrPi9) could execute their interactions with PICI1 in planta, as shown in Zhai et al (2021). Interestingly, AvrPi9 was found to promote PICI1 degradation, which in turns results in increased METS1 ubiquitination and degradation.…”

OsLMP1, Encoding a Deubiquitinase, Regulates the Immune Response in Rice

“…In the absence of pathogen, GmTAP1 remained confined to the cytoplasm and did not modify plant susceptibility. Recent, PICI1, encoding a deubiquitinase, plays as an immunity hub for PTI and ETI in rice ( Zhai et al, 2021 ). PICI1 is targeted for degradation by blast fungal effectors, including AvrPi9, to dampen PTI.…”