?Accumulation of PR proteins in tobacco transplastomic plants results in resistance to pathogenic oomycetes and fungus under field infection conditions?

SEGRETIN, MARÍA EUGENIA; BOCCARDO, NOELIA; HERNÁNDEZ, INGRID; CHACÓN-CHACÓN, OSMANI; LOPEZ, YUNIOR; BORRÁS-HIDALGO, ORLANDO; BRAVO-ALMONACID, FERNANDO FELIX

Foz de Iguazú

Congreso; 11th International Plant Molecular Biology Congress IPMB2015; 2015

Plant diseases affect most staple crops decreasing productivity worldwide compromising foodsecurity. Many attempts have been done to obtain disease resistant crops through transgenesis, with variable results. One strategy is to overexpress pathogenesis-related (PR) proteins and/or express heterologous proteins with antimicrobial activity. For this strategy to be successful, high levels of protein accumulation are required, although this could result in lesion-mimic phenotypes. In order to overcome these limitations, we decided to evaluate plastid transformation as an alternative. Plastome transformation advantages nuclear transformation because of the higher protein expression levels, due to the higher genome copy number, absence of positional effects and silencing. Also the possibility of expressing polycistronic RNAs and maternal inheritance of transgenes. We developed a plastid transformation vector and used it to transform Nicotiana tabacum plastids in order to express two N. tabacum PR proteins, alone or combined as polycistrons: AP24 and -1,3-glucanase. We obtained several transplastomic tobacco lines that were challenged with the fungus pathogen Rhizoctonia solani and the oomycetes Peronospora hyoscyami f.sp. tabacina and Phytophthora nicotianae. The trials were performed in greenhouse conditions for R. solani and in the field for P. hyoscyami f.sp. tabacina and P. nicotianae. Preliminary results showed that transplastomic plants expressing both AP24 and glucanase are highly resistant to R. solani and moreover, are protected against P.hyoscyami f.sp. tabacina and P. nicotianae in field conditions under high inoculum pressure. We are repeating these assays and characterizing the plants by Southern, northern and western-blot. Our results suggest that expression of PR proteins in the chloroplast is a powerful way of engineering a broad-spectrum disease resistance.