A Plant Lectin Receptor-like Kinase Phosphorylates the Bacterial Effector AvrPtoB to Dampen Its Virulence in Arabidopsis

Abstract

Plasma membrane-localized receptor-like kinases (RLKs) perceive conserved pathogen-associated molecular patterns (PAMPs) in plants, leading to PAMP-triggered immunity (PTI). The Arabidopsis thaliana lectin RLK LecRK-IX.2 has been shown to regulate the bacterial flagellin-derived peptide flg22-induced PTI.Here, we discover that Pseudomonas syringae effector AvrPtoB targets LecRK-IX.2 for degradation, which subsequently suppresses LecRK-IX.2-mediated PTI and disease resistance. However, LecRK-IX.2 can interact with and phosphorylate AvrPtoB at serine site 335 (S335). AvrPtoB self-associates in vitro and in vivo, and the association appears to be essential for its E3 ligase activity in ubiquitinating substrate in plants. Phosphorylation of S335 disrupts the self-association and as a result, phosphomimetic AvrP-toB S335D cannot ubiquitinate LecRK-IX.2 efficiently, leading to the compromised virulence of AvrPtoB in suppressing PTI responses. flg22 enhances AvrPtoB S335 phosphorylation by inducing the expression and activating of LecRK-IX.2. Our study demonstrates that host RLKs can modify pathogen effectors to dampen their virulence and undermine their ability in suppressing PTI.

Identification of LecRLK gene family in Cerasus humilis through genomic-transcriptomic data mining and expression analyses

“…Another L-type lecRLK encoding gene ( AtLPK1 ) is related to elevated resistance to Botrytis cinerea [ 38 ]. In addition, the L-type lecRLK LecRK-IX.2 not only can activate the immune responses, but also can phosphorylate the bacterial effector AvrPtoB and thereby potentially can reduce its virulence [ 12 , 39 ]. Several reports showed that L-type LecRLKs are also involved in plants’ responses to abiotic stresses stimuli and plants’ developmental processes [ 40 , 41 ].…”

“…Membrane localized receptor-like kinases (RLKs), together with other signal receptors like phytochromes, act as the first site of signal perception, which allows the plants to communicate between cells and to respond to changes in their environment [1,2]. Lectin receptor-like protein kinase (LecRLK) family is a group of RLKs that have been shown to play several vital roles in plant pathogenic defense, symbiotic association, insect feeding response, innate immunity and different abiotic stress responses, such as low temperature and high salinity [3][4][5][6][7][8][9][10][11][12][13][14]. LecRLKs were firstly discover and examined in Arabidopsis thaliana [15], and were later isolated in a few important food crops, such as Oryza sativa [16], Pisum sativum [17], Solanum lycopersicum [10], Pyrus bretschneideri [2] and Solanum tuberosum [14].…”

Ubiquitination in the rice blast fungus Magnaporthe oryzae: from development and pathogenicity to stress responses

“…Multiple studies showed that ubiquitination-mediated protein degradation play important role in pathogen-host interaction. For example, the effector AvrPtoB, an E3 ligase from Pseudomonas syringae, promotes the degradation of positive plant immunity proteins, including lectin RLK LecRK-IX.2 and EXO70B1, to enhance the Pto DC3000 virulence (Wang et al 2019b;Xu et al 2020). In addition, LecRK-IX.2 reversely phosphorylates AvrPtoB to reduce its E3 ligase activity (Xu et al 2020).…”

“…For example, the effector AvrPtoB, an E3 ligase from Pseudomonas syringae, promotes the degradation of positive plant immunity proteins, including lectin RLK LecRK-IX.2 and EXO70B1, to enhance the Pto DC3000 virulence (Wang et al 2019b;Xu et al 2020). In addition, LecRK-IX.2 reversely phosphorylates AvrPtoB to reduce its E3 ligase activity (Xu et al 2020). In M. oryzae-rice interaction, the effector AvrPiz-t interacts with two RING-type E3 ligases, AVRPIZ-T INTERACTING PROTEIN 6 (APIP6) and APIP10, to suppress their ubiquitin ligase activities and promote their degradation.…”

What the Wild Things Do: Mechanisms of Plant Host Manipulation by Bacterial Type III-Secreted Effector Proteins

“…The full virulence function of AvrPtoB requires in planta phosphorylation at serine-258, which is catalyzed by the Snf1-related kinase SnRK2.8 [ 355 , 356 ]. This can be counteracted, however, by the interaction of AvrPtoB with either Pto kinase or the lectin receptor-like kinase LecRK-IX.2, which phosphorylate AvrPtoB at threonine-450 or serine-335, respectively, to compromise the virulence-promoting E3 ubiquitin ligase activity of the T3SE [ 357 , 358 ]. For AvrPto, phosphorylation at serine-147 and serine-149 is required for its full virulence-promoting activity on susceptible tomato plants [ 359 , 360 ].…”