Pooled effector library screening in protoplasts rapidly identifies novel Avr genes

Arndell, Taj; Chen, Jian; Sperschneider, Jana; Upadhyaya, Narayana M.; Blundell, Cheryl; Niesner, Nathalie; Outram, Megan A.; Wang, Aihua; Swain, Steve; Luo, Ming; Ayliffe, Michael A.; Figueroa, Melania; Vanhercke, Thomas; Dodds, Peter N.

doi:10.1038/s41477-024-01641-y

Cited by 5 publications

(1 citation statement)

References 38 publications

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“…In this way two southern corn rust ( Puccinia polysora ) genes, designated AvrRppC and AvrRppk , were identified that interact with the maize rust resistance genes RppC and RppK respectively [30,31] to give a resistance response. Similarly, two wheat stem rust genes, AvrSr13 and AvrSr22 , were identified that interact with the wheat rust resistance genes Sr13 and Sr22, respectively [32].…”

Section: Discussionmentioning

confidence: 99%

A two-component signature determines which rust fungi secreted proteins are translocated into the cells of the host plant

Lawrence

2024

Preprint

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Rust diseases of plants are caused by parasitic fungi that feed off living plant cells by means of haustoria that form within plant cells. These haustoria also secrete a large number of proteins, some of which remain in the matrix surrounding the haustoria while others are translocated through a membrane into the cytoplasm of the plant cell. These latter proteins would be expected to possess a signature marking them out for translocation but, to date, no such signature has been identified. An examination of a set of wheat rust proteins known to be translocated to the cytoplasm of the wheat cell, together with an analysis of 1208 wheat stem rust (Puccinia graminisf. sp.tritici) secretome proteins, provides evidence that the translocation signature contains two components. The first component consists of a positively-charged amino acid at position 1, 2 or 3 (and possibly 4 or greater) upstream of the hydrophobic region in the signal peptide. The second component consists of a positively-charged amino acid at position 21 downstream of the signal peptide. A similar analysis of flax rust (Melampsora lini) secretome proteins indicates that the first component is the same as that of the wheat stem rust secretome proteins but that the second component consists of a positively-charged amino acid at position (16)17-20 downstream of the signal peptide. The flax rust signature may also be employed by wheat stem rust in its pycnial stage when growing on its alternate dicot host, barberry. Being able to identify which rust haustorial secreted proteins go to the plant cytoplasm and which to the extrahaustorial matrix should facilitate work aimed at identifying the function of each of the secreted proteins and, also, work aimed at elucidating the translocation mechanism, an understanding of which could open up new approaches to rust control.

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Section: Discussionmentioning

confidence: 99%

A two-component signature determines which rust fungi secreted proteins are translocated into the cells of the host plant

Lawrence

2024

Preprint

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Identification of Candidate Avirulence and Virulence Genes Corresponding to Stem Rust (Puccinia graminis f. sp. tritici) Resistance Genes in Wheat

Upadhaya,

Brueggeman

2024

MPMI

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Stem rust, caused by the biotrophic fungal pathogen Puccinia graminis f. sp. tritici (Pgt), is an important disease of wheat. However, the majority of Pgt virulence/avirulence loci and underlying genes remain uncharacterized due to the constraints of developing bi-parental populations with this obligate biotroph. Genome wide association studies (GWAS) using a sexual Pgt population mainly collected from the Pacific Northwestern US were used to identify candidate virulence/avirulence effector genes corresponding to the six wheat Sr genes — Sr5, Sr21, Sr8a, Sr17, Sr9a, and Sr9d. The Pgt isolates were genotyped using whole genome shotgun sequencing identifying ~1.2 million single nucleotide polymorphisms (SNPs) and phenotyped at the seedling stage on six Sr gene differential lines. Association mapping analyses identified 17 Pgt loci associated with virulence or avirulence phenotypes on six Pgt resistance genes. Among these loci, 16 interacted with a specific Sr gene, indicating Sr-gene specific interactions. However, one avirulence locus interacted with two separate Sr genes (Sr9a and Sr17) suggesting two distinct Sr genes identifying a single avirulence effector. A total of 24 unique effector gene candidates were identified and haplotype analysis suggests that within this population AvrSr5, AvrSr21, AvrSr8a, AvrSr17, and AvrSr9a are dominant avirulence genes, while avrSr9d is a dominant virulence gene. The putative effector genes will be fundamental for future effector gene cloning efforts, allowing for further understanding of rust effector biology and the mechanisms underlying virulence evolution in Pgt with respect to race-specific R-genes.

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Comparative Analysis of the Avirulence Effectors Produced by the Fungal Stem Rust Pathogen of Wheat

Lubega,

Figueroa,

Dodds

et al. 2024

MPMI

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Crops are constantly exposed to pathogenic microbes. Rust fungi are examples of these harmful microorganisms which have a major economic impact on wheat production. To protect themselves from pathogens like rust fungi, plants employ a multi-layered immune system that includes immunoreceptors encoded by resistance genes. Significant efforts have led to the isolation of numerous resistance genes against rust fungi in cereals, especially in wheat. However, the evolution of virulence of rust fungi hinders the durability of resistance genes as a strategy for crop protection. Rust fungi like other biotrophic pathogens secrete an arsenal of effectors to facilitate infection, and these are the molecules that plant immunoreceptors target for pathogen recognition and mounting defence responses. When recognized these effector proteins are referred to as avirulence (Avr) effectors. Despite the many predicted effectors in wheat rust fungi only five Avr genes have been identified, all from wheat stem rust. Knowledge of the Avr genes and their variation in the fungal population will inform deployment of the most appropriate wheat disease resistance genes for breeding and farming. The review provides an overview of methodologies as well as the validation techniques that have been used to characterize Avr effectors from wheat stem rust.

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Pooled effector library screening in protoplasts rapidly identifies novel Avr genes

Cited by 5 publications

References 38 publications

A two-component signature determines which rust fungi secreted proteins are translocated into the cells of the host plant

A two-component signature determines which rust fungi secreted proteins are translocated into the cells of the host plant

Identification of Candidate Avirulence and Virulence Genes Corresponding to Stem Rust (Puccinia graminis f. sp. tritici) Resistance Genes in Wheat

Comparative Analysis of the Avirulence Effectors Produced by the Fungal Stem Rust Pathogen of Wheat

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