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1. Four tyrosine residues of the rice immune receptor XA21 are not required for interaction with the co-receptor OsSERK2 or resistance to Xanthomonas oryzae pv. oryzae

   https://doi.org/10.7717/peerj.6074  

   Caddell, Daniel F. ; Wei, Tong ; Sharma, Sweta ; Oh, Man-Ho ; Park, Chang-Jin ; Canlas, Patrick ; Huber, Steven C. ; Ronald, Pamela C. ( December 2018 , PeerJ)

   Tyrosine phosphorylation has emerged as an important regulator of plasma membrane-localized immune receptors activity. Here, we investigate the role of tyrosine phosphorylation in the regulation of riceXANTHOMONASRESISTANCE 21 (XA21)-mediated immunity. We demonstrate that the juxtamembrane and kinase domain ofEscherichia coli–expressed XA21 (XA21JK) autophosphorylates on tyrosine residues. Directed mutagenesis of four out of the nine tyrosine residues in XA21JK reduced autophosphorylation. These sites include Tyr⁶⁹⁸in the juxtamembrane domain, and Tyr⁷⁸⁶, Tyr⁹⁰⁷, and Tyr⁹⁰⁹in the kinase domain. Rice plants expressing XA21-GFP fusion proteins or proteins with these tyrosine residues individually mutated to phenylalanine (XA21^YF-GFP), which prevents phosphorylation at these sites, maintain resistance toXanthomonas oryzaepv.oryzae. In contrast, plants expressing phosphomimetic XA21 variants with tyrosine mutated to aspartate (XA21^YD-GFP) were susceptible. In vitro purified XA21JK^Y698F, XA21JK^Y907F, and XA21JK^Y909Fvariants are catalytically active, whereas activity was not detected in XA21JK^Y768Fand the four XA21JK^YDvariants. We previously demonstrated that interaction of XA21 with the co-receptor OsSERK2 is critical for biological function. Four of the XA21JK^YFvariants maintain interaction with OsSERK2 as well as the XA21 binding (XB) proteins XB3 and XB15 in yeast, suggesting that these four tyrosine residues are not required for their interaction. Taken together, these results suggest that XA21 is capable of tyrosine autophosphorylation, but the identified tyrosine residues are not required for activation of XA21-mediated immunity or interaction with predicted XA21 signaling proteins.

    

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2. Enzymatic Functions for Toll/Interleukin-1 Receptor Domain Proteins in the Plant Immune System

   https://doi.org/10.3389/fgene.2020.00539  

   Bayless, Adam M. ; Nishimura, Marc T. ( June 2020 , Frontiers in Genetics)

   null (Ed.)
3. TurboID-based proximity labeling reveals that UBR7 is a regulator of N NLR immune receptor-mediated immunity

   https://doi.org/10.1038/s41467-019-11202-z  

   Zhang, Yongliang ; Song, Gaoyuan ; Lal, Neeraj K. ; Nagalakshmi, Ugrappa ; Li, Yuanyuan ; Zheng, Wenjie ; Huang, Pin-jui ; Branon, Tess C. ; Ting, Alice Y. ; Walley, Justin W. ; et al ( December 2019 , Nature Communications)
4. A wheat kinase and immune receptor form host-specificity barriers against the blast fungus

   https://doi.org/10.1038/s41477-023-01357-5  

   Arora, Sanu ; Steed, Andrew ; Goddard, Rachel ; Gaurav, Kumar ; O’Hara, Tom ; Schoen, Adam ; Rawat, Nidhi ; Elkot, Ahmed F. ; Korolev, Andrey V. ; Chinoy, Catherine ; et al ( June 2022 , Nature Plants)

   Abstract Since emerging in Brazil in 1985, wheat blast has spread throughout South America and recently appeared in Bangladesh and Zambia. Here we show that two wheat resistance genes, Rwt3 and Rwt4 , acting as host-specificity barriers against non- Triticum blast pathotypes encode a nucleotide-binding leucine-rich repeat immune receptor and a tandem kinase, respectively. Molecular isolation of these genes will enable study of the molecular interaction between pathogen effector and host resistance genes. 

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5. Nuclear transport receptor KA120 regulates molecular condensation of MAC3 to coordinate plant immune activation

   https://doi.org/10.1016/j.chom.2023.08.015  

   Jia, Min ; Chen, Xuanyi ; Shi, Xuetao ; Fang, Yiling ; Gu, Yangnan ( October 2023 , Cell Host & Microbe)

   The nucleocytoplasmic exchange is of fundamental importance to eukaryotic life and is mediated by karyo- pherins, a superfamily of nuclear transport receptors. However, the function and cargo spectrum of plant kar- yopherins are largely obscure. Here, we report proximity-labeling-based proteomic profiling of in vivo sub- strates of KA120, a karyopherin-b required for suppressing autoimmune induction in Arabidopsis. We identify multiple components of the MOS4-associated complex (MAC), a conserved splicing regulatory pro- tein complex. Surprisingly, we find that KA120 does not affect the nucleocytoplasmic distribution of MAC proteins but rather prevents their protein condensation in the nucleus. Furthermore, we demonstrate that MAC condensation is robustly induced by pathogen infection, which is sufficient to activate defense gene expression, possibly by sequestrating negative immune regulators via phase transition. Our study reveals a noncanonical chaperoning activity of a plant karyopherin, which modulates the nuclear condensation of an evolutionarily conserved splicing regulatory complex to coordinate plant immune activation. 

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