Frank You

Toward evidence that homologs of RPW8 act through salicylic acid signaling in powdery mildew resistance in flax
Vanessa Clemis1,2, Mohsin Zaidi, Frank You3, Chunfang Zheng3, Sylvie Cloutier3, and Bourlaye Fofana1
1Charlottetown Research and Development Centre, Agriculture and Agri-Food Canada, 440 University Avenue, Charlottetown, Prince Edward Island, C1A 4N6, Canada
2University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island, C1A 4P3, Canada
3Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, Ontario, K1A 0C6, Canada
*bourlaye.fofana@agr.gc.ca
Powdery mildew (PM) is an obligate biotrophic fungus (Podosphaera lini) causing high yield loss to flax (Linum usitatissimum L.). To date, no PM resistance genes have been fully functionally characterized. Using GWAS, we identified a locus harboring three flax homologs of the Arabidopsis RPW8 genes that confer broad-spectrum resistance to powdery mildew. Here, we characterized the gene expression profile of the three RPW8 candidate genes following PM inoculation. The data showed that, similar to RPW8.2 acting through the salicylic acid (SA) signaling pathway, the RPW8 homologs Lus10000835 and Lus10000836 are highly expressed in resistant flax lines compared to the suscpetible lines. In contrast, the flax RPW8 homolog Lus10009328 was highly expressed in the susceptible lines, suggesting a different signaling pathway from the other two homologs. RPW8.1 has been shown to activate ethylene signaling through aminocyclopropane-1-carboxylate oxidase gene isoform 4 (ACO4) and, this elevated ethylene negatively regulates the expression of RPW8.1, thereby attenuating its mediated-cell death and disease resistance when no disease is present to avoid unnecessary defense responses. We conclude that PM resistance induced by RPW8 in flax may mainly be activated through SA signaling pathways, and perhaps similarly to the ethylene signaling in Arabidopsis.

Cloutier S, Zheng C, Rashid K, Molina O, Edwards T, Lévesque-Lemay, Froese S, Jackle K, House M, Young L, Booker H, Ta’ran B, You F (2023) Fusarium wilt resistance in flax is controlled by a major gene on chromosome 1. Flax Genomics Workshop, Proc 30th Plant and Animal Genome Conference, San Diego, CA, Jan 13-18 (oral – invited)

Cloutier S, Sertse D, Ravichandran S, Duguid S, Soto-Cerda BJ, You FM (2022) Gene banks for crop improvement under climate change: a case study of flax drought. ProciNorte-NORGEN – Task Force on Genetic Resouces, Nov 15, Virtual (oral – invited)

Cloutier S, Fedak G, Fatima F, Bartaula S, McCallum B, Henriquez MA, Blackwell B, Aboukhaddour R, Foster A, Hiebert C, Humphreys G, McCartney C, Pozniak C, You F (2022) Tapping into wild relatives to improve wheat. ProciNorte Disease Task Force Webinars - Wheat & Grapes: Mitigating the effects brought on by climate change, Sept 13 & 15, Virtual (oral – invited)

Cloutier S, Fedak G, Fatima F, Bartaula S, McCallum B, Henriquez MA, Blackwell B, Aboukhaddour R, Foster A, Hiebert C, Humphreys G, Mccartney C, Pozniak C, You F (2022) Wheat Pre-breeding: the struggle(s) and potential. Proc. 37th Plant Sciences Graduate Students’ Symposium 2022, March 4-5, Virtual (oral)

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Fatima, F., McCallum, B.D., Pozniak, C.J., Hiebert, C.W., McCartney, C.A., Fedak, G., You, F.M., Cloutier, S. (2020). Identification of New Leaf Rust Resistance Loci in Wheat and Wild Relatives by Array-Based SNP Genotyping and Association Genetics. Frontiers in Plant Science, [online] 11 http://dx.doi.org/10.3389/fpls.2020.583738

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