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 rice
The rice immune receptor XA21 is activated by the sulfated microbial peptide required for activation of XA21-mediated immunity X (RaxX) produced by
- NSF-PAR ID:
- 10090193
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- Article No. 201818275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
XANTHOMONAS RESISTANCE 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 (XA21YF-GFP), which prevents phosphorylation at these sites, maintain resistance toXanthomonas oryzae pv.oryzae . In contrast, plants expressing phosphomimetic XA21 variants with tyrosine mutated to aspartate (XA21YD-GFP) were susceptible. In vitro purified XA21JKY698F, XA21JKY907F, and XA21JKY909Fvariants are catalytically active, whereas activity was not detected in XA21JKY768Fand the four XA21JKYDvariants. We previously demonstrated that interaction of XA21 with the co-receptor OsSERK2 is critical for biological function. Four of the XA21JKYFvariants 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. -
Pseudokinases are thought to lack phosphotransfer activity due to altered canonical catalytic residues within their kinase domain. However, a subset of pseudokinases maintain activity through atypical phosphotransfer mechanisms. The Arabidopsis ILK1 is a pseudokinase from the Raf-like MAP3K family and is the only known plant pseudokinase with confirmed protein kinase activity. ILK1 activity promotes disease resistance and molecular pattern-induced root growth inhibition through its stabilization of the HAK5 potassium transporter with the calmodulin-like protein CML9. ILK1 also has a kinase-independent function in salt stress suggesting that it interacts with additional proteins. We determined that members of the ILK subfamily are the sole pseudokinases within the Raf-like MAP3K family and identified 179 novel putative ILK1 protein interactors. We also identified 70 novel peptide targets for ILK1, the majority of which were phosphorylated in the presence of Mn 2+ instead of Mg 2+ in line with modifications in ILK1’s DFG cofactor binding domain. Overall, the ILK1-targeted or interacting proteins included diverse protein types including transporters (HAK5, STP1), protein kinases (MEKK1, MEKK3), and a cytokinin receptor (AHK2). The expression of 31 genes encoding putative ILK1-interacting or phosphorylated proteins, including AHK2, were altered in the root and shoot in response to molecular patterns suggesting a role for these genes in immunity. We describe a potential role for ILK1 interactors in the context of cation-dependent immune signaling, highlighting the importance of K + in MAMP responses. This work further supports the notion that ILK1 is an atypical kinase with an unusual cofactor dependence that may interact with multiple proteins in the cell.more » « less
-
Abstract Accurately predicting the impacts of climate change on wildlife health requires a deeper understanding of seasonal rhythms in host–pathogen interactions. The amphibian pathogen,
Batrachochytrium dendrobatidis (Bd ), exhibits seasonality in incidence; however, the role that biological rhythms in host defences play in defining this pattern remains largely unknown.The aim of this study was to examine whether host immune and microbiome defences against
Bd correspond with infection risk and seasonal fluctuations in temperature and humidity.Over the course of a year, five populations of Southern leopard frogs (
Rana [Lithobates ]sphenocephala ) in Tennessee, United States, were surveyed for host immunity, microbiome and pathogen dynamics. Frogs were swabbed for pathogen load and skin bacterial diversity and stimulated to release stored antimicrobial peptides (AMPs). Secretions were analysed to estimate total hydrophobic peptide concentrations, presence of known AMPs and effectiveness ofBd growth inhibition in vitro. The diversity and proportion of bacterial reads with a 99% match to sequences of isolates known to inhibitBd growth in vitro were used as an estimate of predicted anti‐Bd function of the skin microbiome.Batrachochytrium dendrobatidis dynamics followed the expected seasonal fluctuations—peaks in cooler months—which coincided with when host mucosal defences were most potent againstBd . Specifically, the concentration and expression of stored AMPs cycled synchronously withBd dynamics. Although microbiome changes followed more linear trends over time, the proportion of bacteria that can function to inhibitBd growth was greatest when risk ofBd infection was highest.We interpret the increase in peptide storage in the fall and the shift to a more anti‐
Bd microbiome over winter as a preparatory response for subsequent infection risk during the colder periods when AMP synthesis and bacterial growth is slow and pathogen pressure from this cool‐adapted fungus is high. Given that a decrease in stored AMP concentrations as temperatures warm in spring likely means greater secretion rates, the subsequent decrease in prevalence suggests seasonality ofBd in this host may be in part regulated by annual immune rhythms, and dominated by the effects of temperature. -
Summary Fungal phytopathogens can suppress plant immune mechanisms in order to colonize living host cells. Identifying all the molecular components involved is critical for elaborating a detailed systems‐level model of plant infection probing pathogen weaknesses; yet, the hierarchy of molecular events controlling fungal responses to the plant cell is not clear.
Here we show how, in the blast fungus
Magnaporthe oryzae , terminating rice innate immunity requires a dynamic network of redox‐responsive E3 ubiquitin ligases targeting fungal sirtuin 2 (Sir2), an antioxidation regulator required for suppressing the host oxidative burst.Immunoblotting, immunopurification, mass spectrometry and gene functional analyses showed that Sir2 levels responded to oxidative stress via a mechanism involving ubiquitination and three antagonistic E3 ubiquitin ligases: Grr1 and Ptr1 maintained basal Sir2 levels in the absence of oxidative stress; Upl3 facilitated Sir2 accumulation in response to oxidative stress. Grr1 and Upl3 interacted directly with Sir2 in a manner that decreased and scaled with oxidative stress, respectively.
Deleting
UPL3 depleted Sir2 during growth in rice cells, triggering host immunity and preventing infection. OverexpressingSIR2 in the Δupl3 mutant remediated pathogenicity. Our work reveals how redox‐responsive E3 ubiquitin ligases inM. oryzae mediate Sir2 accumulation‐dependent antioxidation to modulate plant innate immunity and host susceptibility. -
Abstract Macrophages are a predominant immune cell population that drive inflammatory responses and exhibit transitions in phenotype and function during tissue remodeling in disease and repair. Thus, engineering an immunomodulatory biomaterial has significant implications for resolving inflammation. Here, a biomimetic and photoresponsive hyaluronan (HA) hydrogel nanocomposite with tunable 3D extracellular matrix (ECM) adhesion sites for dynamic macrophage immunomodulation is engineered. Photodegradative alkoxylphenacyl‐based polycarbonate (APP) nanocomposites are exploited to permit user‐controlled Arg–Gly–Asp (RGD) adhesive peptide release and conjugation to a HA‐based ECM for real‐time integrin activation of macrophages encapsulated in 3D HA–APP nanocomposite hydrogels. It is demonstrated that photocontrolled 3D ECM–RGD peptide conjugation can activate αvβ3 integrin of macrophages, and periodic αvβ3 integrin activation can enhance anti‐inflammatory M2 macrophage polarization. Altogether, an emerging use of biomimetic, photoresponsive, and bioactive HA–APP nanocomposite hydrogel is highlighted to command 3D cell–ECM interactions for modulating macrophage polarization, which may shed light on cell–ECM interactions in innate immunity and inspire new biomaterial‐based immunomodulatory therapies.