A Puccinia striiformis f. sp. tritici secreted protein activates plant immunity at the cell surface

Abstract

Pathogens secrete effector proteins to suppress host immunity, mediate nutrient uptake and subsequently enable parasitism. However, on non-adapted hosts, effectors can be detected as non-self by host immune receptors and activate non-host immunity. Nevertheless, the molecular mechanisms of effector triggered non-host resistance remain unknown. Here, we report that a small cysteine-rich protein PstSCR1 from the wheat rust pathogen Puccinia striiformis f. sp. tritici (Pst) activates immunity in the non-host solanaceous model plant Nicotiana benthamiana. PstSCR1 homologs were found to be conserved in Pst, and in its closest relatives, Puccinia graminis f. sp. tritici and Puccinia triticina. When PstSCR1 was expressed in N. benthamiana with its signal peptide, it provoked the plant immune system, whereas no stimulation was observed when it was expressed without its signal peptide. PstSCR1 expression in N. benthamiana significantly reduced infection capacity of the oomycete pathogens. Moreover, apoplast-targeted PstSCR1 triggered plant cell death in a dose dependent manner. However, in Brassinosteroid insensitive 1-Associated Kinase 1 (SERK3/BAK1) silenced N. benthamiana, cell death was remarkably decreased. Finally, purified PstSCR1 protein activated defence related gene expression in N. benthamiana. Our results show that a Pst-secreted protein, PstSCR1 can activate surface mediated immunity in non-adapted hosts and contribute to non-host resistance.

A Near-Complete Haplotype-Phased Genome of the Dikaryotic Wheat Stripe Rust FungusPuccinia striiformisf. sp.triticiReveals High Interhaplotype Diversity

“…The diversity of plant pathogen effectors makes them impossible to identify based on protein sequences alone ( 58 ). Only a small number of effectors have thus far been confirmed in rust fungi, namely, AvrP123, AvrP4, AvrL567, AvrM, RTP1, PGTAUSPE-10-1 ( 59 ), AvrL2 and AvrM14 ( 60 ), PstSCR1 ( 61 ) and PEC6 ( 62 ). At the sequence level, effectors do not share common domains or motifs, apart from the presence of a signal peptide.…”

Foxtail mosaic virus: A Viral Vector for Protein Expression in Cereals

“…This limits the experimental throughput. Furthermore, avoiding this first step of virus inoculum buildup in N. benthamiana may be necessary when testing constructs for the expression of generic cell death-inducing proteins (Lacomme and Santa Cruz, 1999;Tang et al, 2015;Kettles et al, 2018), predicted proteinaceous pathogen-associated molecular patterns (Franco-Orozco et al, 2017), or certain candidate pathogen effector proteins that may be recognized by the corresponding immune receptors in this plant species (Dagvadorj et al, 2017;Kettles et al, 2017). Therefore, we assessed the possibility of delivering the FoMV VOX vector directly into wheat leaves using infiltration with the recAdeficient A. tumefaciens strain COR308 harboring the disarmed pTi derivative plasmid pMP90 and the helper plasmid pCH32, which provide extra copies of the virA and virG genes (Hamilton, 1997), and a corresponding protocol that was claimed to be efficient in delivering BSMV-derived gene-silencing constructs directly to wheat leaves (Panwar et al, 2013).…”

Whole-genome sequencing of Puccinia striiformis f. sp. tritici mutant isolates identifies avirulence gene candidates

“…To date, a handful of Avr genes have been molecularly identified in rust pathogens, including AvrL567, AvrP123, AvrP4, AvrM, AvrL2 and AvrM14 from the flax rust pathogen Melampsora lini (M. lini) together with PGTAUSPE10-1, AvrSr35 and AvrSr50 from Pgt [18,[25][26][27][28]. In Pst, Dagvadorj et al [29] reported that PstSCR1 can activate immunity in non-host plants. Zhao et al [30] found that Pst_8713 was involved in enhancing Pst virulence and suppressing plant immunity.…”