|KAUR, JAGDEEP - Danforth Plant Science Center|
|EL-MOUNADI, KAOTAR - Danforth Plant Science Center|
|NERSESIAN, NATALYA - University Of Nebraska|
|CLEMENTE, THOMAS - University Of Nebraska|
|SHAH, DILIP - Danforth Plant Science Center|
Submitted to: Transgenic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2016
Publication Date: 8/31/2016
Publication URL: http://handle.nal.usda.gov/10113/63193
Citation: Kaur, J., Fellers, J.P., El-Mounadi, K., Nersesian, N., Clemente, T., Shah, D. 2016. Expression of apoplast-targeted plant defensin MtDef4.2 confers resistance to leaf rust pathogen Puccinia triticina but does not affect mycorrhizal symbiosis in transgenic wheat. Transgenic Research. https://doi.org/10.1007/s11248-016-9978-9.
Interpretive Summary: Plants have many ways of defending against pathogens that attack and cause diseases. Most commonly, there are resistance genes that recognize specific pathogens. However, there are more general defenses that can be effective against many pathogens and are found in both animals and plants. One such class is called defensins. These are small proteins that can bind to membranes or target important proteins and cause the pathogen to die. In this research, a defensin called MtDet4.2 from a relative of alfalfa was cloned and transformed into wheat. Wheat lines with MtDef4.2 were tested with a race of leaf rust and found to be resistant. The wheat lines were further characterized for expression of both plant and leaf rust genes that are associated with infection. This work shows that defensins from other plant species could be useful for new sources of resistance to leaf rust.
Technical Abstract: Rust diseases caused by Puccinia spp. pose a major threat to global wheat production. Puccinia triticina (Pt), an obligate basidiomycete biotroph, causes leaf rust disease which incurs yield losses of up to 50% in wheat. Historically, resistant wheat cultivars have been used to control leaf rust, but resistance is ephemeral that breaks down with the emergence of new virulent Pt races. We have investigated a transgenic approach as a means to complement endogenous resistance alleles within the wheat germplasm thereby providing a durable resistance to Pt. To this end, two different genotypes of wheat were transformed with a chimeric gene encoding an antifungal plant defensin MtDef4.2 and plants from four independent events were further characterized. Homozygous plants from two events showed strong resistance to Pt race MCPSS in greenhouse bioassays relative to corresponding non-transgenic controls. Histopathological analysis suggested the combination of both pre- and posthaustorial resistance in these events. Surprisingly, expression of several Pt genes encoding putative avirulence proteins and host genes encoding pathogenesis-related proteins, was induced in Pt resistant wheat upon fungal challenge. This study demonstrated that ectopic expression of an apoplast-targeted antifungal defensin can confer effective resistance to an economically important leaf rust disease in transgenic wheat.