EF-Tu receptor

Last updated
LRR receptor-like serine/threonine-protein kinase EFR
Identifiers
Organism Arabidopsis thaliana
SymbolEFR
UniProt C0LGT6
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Structures Swiss-model
Domains InterPro
EF-Tu (blue) is the ligand of EFR 081-EF-Tu-1ttt.jpg
EF-Tu (blue) is the ligand of EFR
EFR enables an immune response to elf18, a sequence of EF-Tu EFR-1.png
EFR enables an immune response to elf18, a sequence of EF-Tu

EF-Tu receptor, abbreviated as EFR, is a pattern-recognition receptor (PRR) that binds to the prokaryotic protein EF-Tu (elongation factor thermo unstable) in Arabidopsis thaliana (and other members of Brassicaceae). This receptor is an important part of the plant immune system as it allows the plant cells to recognize and bind to EF-Tu, preventing genetic transformation by and protein synthesis in pathogens such as Agrobacterium. [2]

Contents

Background

The plant Arabidopsis thaliana has a genome with only around 135 megabase pairs (Mbp), making it small enough to fully synthesize. It also makes it relatively easy to study, leading to its use as a common model organism in the field of plant genetics. [3] [4] One important use of A. thaliana is in the study of plant immunity. Plant pathogens are able to travel through a plant's vascular system, but plants do not have specific immune cells that can travel this way. Plants also do not have an adaptive immune system, so other forms of immunity are required. One is the use of pattern-recognition receptors (PRR) to bind to pathogen-associated molecular patterns (PAMP), which are highly conserved structures on the outside of many invasive organisms. This form of immunity acts on intercellular pathogens, which are ones outside of individual plant cells. PRRs are transmembrane proteins, which have an anchor inside the cell and portions that extend beyond the membrane. They are part of the innate immune system and bind to and prevent the proliferation of pathogens with the PAMPs that they can bind. [5]

EF-Tu, a very common and highly conserved protein, is an example of a PAMP that can be found in numerous pathogens. [6] Its function as an elongation factor means that it helps create new proteins during translation in the ribosome. When a protein is being formed, amino acids are connected in a long sequence, known as a protein's primary structure. Elongation factors help coordinate the movement of transfer RNAs (tRNA) and messenger RNAs (mRNA) so they stay aligned as the ribosome translocates along the mRNA chain. [7] Due to its importance in ensuring the accuracy of translation and preventing mutations, EF-Tu is a good target of both immune systems and drug therapies designed to prevent infections and subsequent diseases. [8]

Biological function

Synthesis

EFR, like other proteins, undergoes translation in a cell's ribosomes. After the primary structure of the protein has been formed it must fold into its three dimensional tertiary structure to become functional. This occurs in the endoplasmic reticulum (ER). While in the ER, this primary polypeptide chain undergoes a regulatory process known as ER-quality control (ER-QC) to help ensure it folds into the correct 3-D structure. ER-QC process consists of a series of chaperone proteins that help guide the folding of the EFR polypeptide chains, preventing the aggregation of many polypeptide chains into one large group. Proteins that have not folded are kept in the ER until they have folded into their correct 3-D shape. If folding does not occur then the unfolded protein is eventually destroyed. [9] [10]

One of the control mechanisms of EFR is the protein Arabidopsis stromal-derived factor-2 (SDF2). A genetic variant of the A. thaliana plant that did not have the gene to encode for this protein had a far lower production of functional EFR proteins. SDF2 also cannot be substituted for other enzymes in EFR production. Experimental analysis indicated that EFR is destroyed in the cell when it is produced without SDF2, though the mechanism of this action is unknown. Other proteins that are required for the proper synthesis of EFR include Arabidopsis CRT3 and UGGT, which are members of the EFR-QC and act as chaperones to help folding. [10]

Role in plant immunity

EFR receptors have a high affinity for the EF-Tu PAMP. This has been proven analytically through competitive binding assays and SDS-PAGE analysis. When EFR binds to EF-Tu, the basal resistance is activated. [2] This response happens after an infection has already been established and it is important to the plant immune system because it prevents the spread of the pathogen throughout the plant. [11] Only bacteria that have a high amount of EF-Tu are effectively inhibited by EFR, such as Agrobacterium tumefaciens. [2]

Similarities to FLS2

Like EFR, FLS2 (flagellin-sensing 2) is a plant receptor-like kinase that acts as a PRR in the plant innate immune system. [10] [12] Instead of binding to EF-Tu, it binds to flagellin, another highly conserved structure present on many pathogens. Flagellin, like EF-Tu, is a good target for the plant immune system since it is so widespread. It also triggers an immune response in a larger variety of plants than EF-Tu. [2] The immune response triggered by FLS2 is very similar to the one that is triggered by EFR and the enzymes that are activated by both receptors likely come from a common pool that is found in many cells. This indicates that the two receptor pathways converge, which has been shown to occur at the ion channels in the plasma membrane. [10] [13] By perceiving multiple PAMPs, a plant is able to respond to a pathogenic infection more quickly and efficiently, as well as respond to a wider array of pathogens. [10]

Applications

EFR is found only in the plant family Brassicaceae, meaning it has a limited effect in nature. [2] Experiments have demonstrated the ability to successfully transfer EFR to plants in other families, such as Nicotiana benthamiana , a relative of tobacco, and Solanum lycopersicum , the tomato plant. The ability to transfer PRRs between plants and have them retain their effectiveness broadens genetic engineering techniques to promote disease resistance in crops. It can also reduce chemical wastes associated with mass agriculture and enable the transfer of immunity rapidly and without traditional breeding. [14]

See also

Related Research Articles

<i>Arabidopsis thaliana</i> Model plant species in the family Brassicaceae

Arabidopsis thaliana, the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed.

<span class="mw-page-title-main">Calmodulin</span> Messenger protein

Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the binding of Ca2+ is required for the activation of calmodulin. Once bound to Ca2+, calmodulin acts as part of a calcium signal transduction pathway by modifying its interactions with various target proteins such as kinases or phosphatases.

<span class="mw-page-title-main">Flagellin</span> Bacterial protein

Flagellin is a globular protein that arranges itself in a hollow cylinder to form the filament in a bacterial flagellum. It has a mass of about 30,000 to 60,000 daltons. Flagellin is the principal component of bacterial flagella, and is present in large amounts on nearly all flagellated bacteria.

<span class="mw-page-title-main">Toll-like receptor</span> Pain receptors and inflammation

Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system. They are single-spanning receptors usually expressed on sentinel cells such as macrophages and dendritic cells, that recognize structurally conserved molecules derived from microbes. Once these microbes have reached physical barriers such as the skin or intestinal tract mucosa, they are recognized by TLRs, which activate immune cell responses. The TLRs include TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR8, TLR9, TLR10, TLR11, TLR12, and TLR13. Humans lack genes for TLR11, TLR12 and TLR13 and mice lack a functional gene for TLR10. The receptors TLR1, TLR2, TLR4, TLR5, TLR6, and TLR10 are located on the cell membrane, whereas TLR3, TLR7, TLR8, and TLR9 are located in intracellular vesicles.

Pathogen-associated molecular patterns (PAMPs) are small molecular motifs conserved within a class of microbes, but not present in the host. They are recognized by toll-like receptors (TLRs) and other pattern recognition receptors (PRRs) in both plants and animals. This allows the innate immune system to recognize pathogens and thus, protect the host from infection.

Pattern recognition receptors (PRRs) play a crucial role in the proper function of the innate immune system. PRRs are germline-encoded host sensors, which detect molecules typical for the pathogens. They are proteins expressed mainly by cells of the innate immune system, such as dendritic cells, macrophages, monocytes, neutrophils, as well as by epithelial cells, to identify two classes of molecules: pathogen-associated molecular patterns (PAMPs), which are associated with microbial pathogens, and damage-associated molecular patterns (DAMPs), which are associated with components of host's cells that are released during cell damage or death. They are also called primitive pattern recognition receptors because they evolved before other parts of the immune system, particularly before adaptive immunity. PRRs also mediate the initiation of antigen-specific adaptive immune response and release of inflammatory cytokines.

<span class="mw-page-title-main">Innate immune system</span> One of the two main immunity strategies

The innate, or nonspecific, immune system is one of the two main immunity strategies in vertebrates. The innate immune system is an alternate defense strategy and is the dominant immune system response found in plants, fungi, insects, and primitive multicellular organisms.

Systemic acquired resistance (SAR) is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen. SAR is analogous to the innate immune system found in animals, and although there are many shared aspects between the two systems, it is thought to be a result of convergent evolution. The systemic acquired resistance response is dependent on the plant hormone, salicylic acid.

<span class="mw-page-title-main">EF-Tu</span> Prokaryotic elongation factor

EF-Tu is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome. It is a G-protein, and facilitates the selection and binding of an aa-tRNA to the A-site of the ribosome. As a reflection of its crucial role in translation, EF-Tu is one of the most abundant and highly conserved proteins in prokaryotes. It is found in eukaryotic mitochondria as TUFM.

The gene-for-gene relationship is a concept in plant pathology that plants and their diseases each have single genes that interact with each other during an infection. It was proposed by Harold Henry Flor who was working with rust (Melampsora lini) of flax (Linum usitatissimum). Flor showed that the inheritance of both resistance in the host and parasite ability to cause disease is controlled by pairs of matching genes. One is a plant gene called the resistance (R) gene. The other is a parasite gene called the avirulence (Avr) gene. Plants producing a specific R gene product are resistant towards a pathogen that produces the corresponding Avr gene product. Gene-for-gene relationships are a widespread and very important aspect of plant disease resistance. Another example can be seen with Lactuca serriola versus Bremia lactucae.

<span class="mw-page-title-main">EF-G</span> Prokaryotic elongation factor

EF-G is a prokaryotic elongation factor involved in protein translation. As a GTPase, EF-G catalyzes the movement (translocation) of transfer RNA (tRNA) and messenger RNA (mRNA) through the ribosome.

Resistance genes (R-Genes) are genes in plant genomes that convey plant disease resistance against pathogens by producing R proteins. The main class of R-genes consist of a nucleotide binding domain (NB) and a leucine rich repeat (LRR) domain(s) and are often referred to as (NB-LRR) R-genes or NLRs. Generally, the NB domain binds either ATP/ADP or GTP/GDP. The LRR domain is often involved in protein-protein interactions as well as ligand binding. NB-LRR R-genes can be further subdivided into toll interleukin 1 receptor (TIR-NB-LRR) and coiled-coil (CC-NB-LRR).

<span class="mw-page-title-main">Plant disease resistance</span> Ability of a plant to stand up to trouble

Plant disease resistance protects plants from pathogens in two ways: by pre-formed structures and chemicals, and by infection-induced responses of the immune system. Relative to a susceptible plant, disease resistance is the reduction of pathogen growth on or in the plant, while the term disease tolerance describes plants that exhibit little disease damage despite substantial pathogen levels. Disease outcome is determined by the three-way interaction of the pathogen, the plant and the environmental conditions.

BRI1-associated receptor kinase 1 is an important plant protein that has diverse functions in plant development.

Mitogen-activated protein kinase (MAPK) networks are the pathways and signaling of MAPK, which is a protein kinase that consists of amino acids serine and threonine. MAPK pathways have both a positive and negative regulation in plants. A positive regulation of MAPK networks is to help in assisting with stresses from the environment. A negative regulation of MAPK networks is pertaining to a high quantity of reactive oxygen species (ROS) in the plant.

<span class="mw-page-title-main">Leucine-rich repeat receptor like protein kinase</span>

Leucine-rich repeat receptor like protein kinase are plant cell membrane localized Leucine-rich repeat (LRR) receptor kinase that play critical roles in plant innate immunity. Plants have evolved intricate immunity mechanism to combat against pathogen infection by recognizing Pathogen Associated Molecular Patterns (PAMP) and endogenous Damage Associated Molecular Patterns (DAMP). PEPR 1 considered as the first known DAMP receptor of Arabidopsis.

<span class="mw-page-title-main">High Affinity K+ transporter HAK5</span>

High Affinity K+ transporter HAK5 is a transport protein found on the cell surface membrane of plants under conditions of potassium deprivation. It is believed to act as a symporter for protons and the potassium ion, K+. Firstly discovered in barley, receiving the name of HvHAK1, it was soon after identified in the model plant Arabidopsis thaliana and named HAK5. These transporters belongs to the subgroup I of the KT-HAK-KUP family of plant proteins with obvious homology with both bacterial and fungal transport systems, which experienced a major diversification following land conquest. KT-HAK-KUP transporters are one of four different types of K+ transporter within the cell, but are unique as they do not have a putative pore forming domain like the other three; Shaker channels, KCO channels, HKT transporters. It is activated when the plant is situated in low soil with low potassium concentration, and has been shown to be located in higher concentration in the epidermis and vasculature of K+ deprived plants. By turning on, it increases the plants affinity (uptake) of potassium. Potassium plays a vital role in the plants growth, reproduction, immunity, ion homeostasis, and osmosis, which ensures the plants survival. It is the highest cationic molecule within the plant, accounting for 10% of the plants dry weight, which makes its uptake into the plant important. Each plant species has its own HAK5 transporter that is specific to that species and has different levels of affinity to K+. To operate and activate the HAK5 transporter, the external concentration of K+ must be lower than 10μM and up to 200μM. In Arabidopsis plants, when external potassium concentration is lower than 10μM, it is only HAK5 that is involved with the uptake of K+, then between 10 and 200μM both HAK5 and AKT1 are involved with the uptake of K+. HAK5 is coupled with CBL9/CIPK23 kinase's although the mechanism behind this has not yet been understood.

Feronia, also known as FER or protein Sirene, is a recognition receptor kinase found in plants. FER plays a significant part in the plant immune system as a receptor kinase which assists in immune signaling within plants, plant growth, and plant reproduction. FER is regulated by the Rapid Alkalinization Factor (RALF). FER regulates growth in normal environments but it is most beneficial in stressful environments as it helps to initiate immune signaling. FER can also play a role in reproduction in plants by participating in the communication between the female and male cells. FER is found in and can be studied in the organism Arabidopsis thaliana.

<span class="mw-page-title-main">FLS2</span>

FLS genes have been discovered to be involved in flagellin reception of bacteria. FLS1 was the original gene discovered shown to correspond with a specific ecotype within Arabidopsis thaliana. Even so, further studies have shown a second FLS gene known as FLS2 that is also associated with flagellin reception. FLS2 and FLS1 are different genes with different responsibilities, but are related genetically. FLS2 has a specific focus in plant defense and is involved in promoting the MAP kinase cascade. Mutations in the FLS2 gene can cause bacterial infection by lack of response to flg22. Therefore,FLS2’s primary focus is association with flg22 while its secondary focus is the involvement of promoting the MAP kinase cascade in plant defense.

<span class="mw-page-title-main">Brassinosteroid insensitive-1</span>

Brassinosteroid insensitive 1 (BRI1) is the major receptor of the plant hormone brassinosteroid. It plays very important roles in plant development, especially in the control of cell elongation and for the tolerance of environmental stresses. BRI1 enhances cell elongation, promotes pollen development, controls vasculature development and promotes chilling and freezing tolerance. BRI1 is one of the most well studied hormone receptors and it acts a model for the study of membrane-bound receptors in plants.

References

  1. ↑ "PDB-101: Elongation Factors". pdb101.rcsb.org. Retrieved 2017-10-09.
  2. 1 2 3 4 5 6 Zipfel, Cyril; Kunze, Gernot; Chinchilla, Delphine; Caniard, Anne; Jones, Jonathan D.G.; Boller, Thomas; Felix, Georg (2006). "Perception of the Bacterial PAMP EF-Tu by the Receptor EFR Restricts Agrobacterium-Mediated Transformation". Cell. 125 (4): 749–760. doi: 10.1016/j.cell.2006.03.037 . PMID   16713565.
  3. ↑ "TAIR - Genome Assembly". www.arabidopsis.org. Retrieved 2017-10-09.
  4. ↑ Rensink, W. A.; Buell, C. Robin (2004-06-01). "Arabidopsis to Rice. Applying Knowledge from a Weed to Enhance Our Understanding of a Crop Species". Plant Physiology. 135 (2): 622–629. doi:10.1104/pp.104.040170. ISSN   0032-0889. PMC   514098 . PMID   15208410.
  5. ↑ Jones, Jonathan D. G.; Dangl, Jeffery L. (2006-11-16). "The plant immune system". Nature. 444 (7117): 323–329. Bibcode:2006Natur.444..323J. doi: 10.1038/nature05286 . ISSN   0028-0836. PMID   17108957.
  6. ↑ Yamamoto, Hiroshi; Qin, Yan; Achenbach, John; Li, Chengmin; Kijek, Jaroslaw; Spahn, Christian M. T.; Nierhaus, Knud H. (February 2014). "EF-G and EF4: translocation and back-translocation on the bacterial ribosome". Nature Reviews Microbiology. 12 (2): 89–100. doi:10.1038/nrmicro3176. ISSN   1740-1526. PMID   24362468. S2CID   27196901.
  7. ↑ Ramakrishnan, V. (2002-02-22). "Ribosome structure and the mechanism of translation". Cell. 108 (4): 557–572. doi: 10.1016/S0092-8674(02)00619-0 . ISSN   0092-8674. PMID   11909526.
  8. ↑ Krab, Ivo M.; Parmeggiani, Andrea (2002). "Mechanisms of EF-Tu, a pioneer GTPase". Progress in Nucleic Acid Research and Molecular Biology. 71: 513–551. doi:10.1016/S0079-6603(02)71050-7. ISBN   9780125400718. ISSN   0079-6603. PMID   12102560.
  9. ↑ Anelli, Tiziana; Sitia, Roberto (2008-01-23). "Protein quality control in the early secretory pathway". The EMBO Journal. 27 (2): 315–327. doi:10.1038/sj.emboj.7601974. ISSN   0261-4189. PMC   2234347 . PMID   18216874.
  10. 1 2 3 4 5 Nekrasov, Vladimir; Li, Jing; Batoux, Martine; Roux, Milena; Chu, Zhao-Hui; Lacombe, Severine; Rougon, Alejandra; Bittel, Pascal; Kiss‐Papp, Marta (2009-11-04). "Control of the pattern‐recognition receptor EFR by an ER protein complex in plant immunity". The EMBO Journal. 28 (21): 3428–3438. doi:10.1038/emboj.2009.262. ISSN   0261-4189. PMC   2776097 . PMID   19763086.
  11. ↑ Niks, Rients E.; Marcel, Thierry C. (2009-06-01). "Nonhost and basal resistance: how to explain specificity?". New Phytologist. 182 (4): 817–828. doi: 10.1111/j.1469-8137.2009.02849.x . ISSN   1469-8137. PMID   19646067.
  12. ↑ Gómez-Gómez, L.; Boller, T. (June 2000). "FLS2: an LRR receptor-like kinase involved in the perception of the bacterial elicitor flagellin in Arabidopsis". Molecular Cell. 5 (6): 1003–1011. doi: 10.1016/S1097-2765(00)80265-8 . ISSN   1097-2765. PMID   10911994.
  13. ↑ Jeworutzki, Elena; Roelfsema, M. Rob G.; Anschütz, Uta; Krol, Elzbieta; Elzenga, J. Theo M.; Felix, Georg; Boller, Thomas; Hedrich, Rainer; Becker, Dirk (2010-05-01). "Early signaling through the Arabidopsis pattern recognition receptors FLS2 and EFR involves Ca2+-associated opening of plasma membrane anion channels". The Plant Journal. 62 (3): 367–378. doi: 10.1111/j.1365-313X.2010.04155.x . ISSN   1365-313X. PMID   20113440.
  14. ↑ Lacombe, Séverine; Rougon-Cardoso, Alejandra; Sherwood, Emma; Peeters, Nemo; Dahlbeck, Douglas; van Esse, H. Peter; Smoker, Matthew; Rallapalli, Ghanasyam; Thomma, Bart P. H. J. (April 2010). "Interfamily transfer of a plant pattern-recognition receptor confers broad-spectrum bacterial resistance". Nature Biotechnology. 28 (4): 365–369. doi:10.1038/nbt.1613. ISSN   1087-0156. PMID   20231819. S2CID   7260214.
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