Wheat Encodes Small, Secreted Proteins That Contribute to Resistance to Septoria Tritici Blotch

Abstract

During plant-pathogen interactions, pathogens secrete many rapidly evolving, small secreted proteins (SSPs) that can modify plant defense and permit pathogens to colonize plant tissue. The fungal pathogen Zymoseptoria tritici is the causal agent of Septoria tritici blotch (STB), one of the most important foliar diseases of wheat, globally. Z. tritici is a strictly apoplastic pathogen that can secrete numerous proteins into the apoplast of wheat leaves to promote infection. We sought to determine if, during STB infection, wheat also secretes small proteins into the apoplast to mediate the recognition of pathogen proteins and/or induce defense responses. To explore this, we developed an SSP-discovery pipeline to identify small, secreted proteins from wheat genomic data. Using this pipeline, we identified 6,998 SSPs, representing 2.3% of all proteins encoded by the wheat genome. We then mined a microarray dataset, detailing a resistant and susceptible host response to STB, and identified 141 Z. tritici-responsive SSPs, representing 4.7% of all proteins encoded by Z. tritici-responsive genes. We demonstrate that a subset of these SSPs have a functional signal peptide and can interact with Z. tritici SSPs. Transiently silencing two of these wheat SSPs using virusinduced gene silencing (VIGS) shows an increase in susceptibility to STB, confirming their role in defense against Z. tritici.

Genome-Wide Screening of Broad-Spectrum Resistance to Leaf Rust (Puccinia triticina Eriks) in Spring Wheat (Triticum aestivum L.)

“…Due to the near distance between our identified gene model and the previous findings, we can conclude that 6D chromosome seems to carry important genes which are effective against a wide range of Pt races. The second common gene model identified on 6D chromosome (TraesCS6D02G389600) was found to control the disease resistance in wheat indirectly by controlling signal peptide peptidase-like protein, one of wheat secret proteins which enable it to resist foliar disease like LR ( Zhou et al, 2020 ). It was reported that rust pathogen destroys the host cell by producing hydrolase enzyme that degrades the host plant proteins ( Pinter et al, 2019 ).…”

Insights into the resistance of a synthetically-derived wheat to Septoria tritici blotch disease: less is more

“…Z. tritici was cultured by inoculating potato dextrose agar (PDA) with 10 μl of the glycerol stock and incubating the Petri dishes under near-ultraviolet light for 7 days at 20 °C, 12:12 h light:dark cycle). Inoculum was prepared as described in Zhou et al , (2020) [ 50 ], ,and adjusted to a solution of 1 × 10 6 spores ml − 1 + 0.02% Tween20. (Fisher Bioreagents, USA).…”

A small secreted protein from Zymoseptoria tritici interacts with a wheat E3 ubiquitin ligase to promote disease

“…Only yeast cells co-expressing ZtSSP2 and TaE3UBQ 126–219 grew on selective medium (SD/-Leu-Trp-His) (middle panel) and showed α-galactosidase activity encoded by α-galactosidase (MEL1) (right panel). BD-TaSSP6 and AD-Zt06 were used as positive controls ( Zhou et al , 2020 ). The experiment was repeated independently three times, three plates per experiment with similar results.…”

“…Analysis of protein–protein interactions was performed using the Gal4 two-hybrid assay as described in Perochon et al (2010) . As a negative control to ensure specific interactions with ZtSSP2, another small secreted effector candidate (ΔSP) Zt-10 was used ( Kettles et al , 2017 ), while the positive control included TaSSP6 and Zt-06 ( Zhou et al , 2020 ).…”