Host-induced gene silencing of the amino acid biosynthesis gene acetolactate synthase of Phytophthora infestans caused strong enhanced late blight resistance of potato in the field

Nora Temme, Tobias Haehre, Clarissa Boyher, Lydia Hoppe, Colin Davenport, Zach Stumo, Kai Prenzler, Anja Maeser, Maike Pflugmacher, Kerstin Koch, Dietmar J Stahl

Plant Biotechnol J.; 2025 May 9.  doi: 10.1111/pbi.70133.

Abstract

Late blight caused by Phytophthora infestans is the most serious disease of potatoes. Here we present the effectiveness of the host-induced gene silencing (HIGS) technology against an amino acid biosynthesis gene of the pathogen to increase the resistance against the plant-infecting oomycete in the field. A RNAi hairpin construct directed against the acetolactate synthase (ALS) gene of Phytophthora infestans was transferred into potato. HIGS-ALS potato lines displayed efficient target gene silencing revealed by a luciferase reporter gene assay. Plant-derived siRNAs targeting the oomycete's ALS gene were detected by small RNA sequencing. ALS gene expression of P. infestans was reduced during the early infection stages of HIGS-ALS potatoes, as shown by qRT-PCR. HIGS-ALS plants revealed an enhanced late blight resistance in detached leaf assays. ALS gene silencing also conferred strong enhanced late blight resistance to the HIGS lines in trials under near-field conditions in Europe and in field trials in the USA against European and US P. infestans isolates, respectively. These results demonstrated the value of the HIGS technology for the development of a new quantitative resistance source for potato against Phytophthora infestans.

See https://pubmed.ncbi.nlm.nih.gov/40344624/

Figure 1: Generation of HIGS-ALS potato lines by Agrobacterium-mediated transformation. (a) Scheme of the genomic organization of the PiALS gene. The four exons of the gene are shown as boxes and the three introns as bars. Numbers describe the size of exons and introns in bp. (b) Scheme of the RNA_i PiALS cassette of the dsRNA hairpin construct pRNAi-ALS-Kan. Expression of the hairpin construct is controlled by the promoter and terminator of the CaMV 35S gene (white box). The hairpin cassette is composed of exon 4 from the PiALS gene (grey box) in sense and antisense orientation and the intron of the AAP6 gene from Arabidopsis thaliana (white box). The arrows describe the orientation of the sense strand from the PiALS exon 4. (c) Scheme of the reporter gene cassette of the transcriptional luciferase fusion construct pd35S-Luc-ALS_exon4. Expression of the reporter gene construct is controlled by the promoter and terminator of the CaMV 35S gene (white box). Exon 4 of the PiALS gene (grey box) is inserted downstream of the luciferase gene of Photinus pyralis. The luciferase gene is encoded by the exon 1 and 2 sequences (white boxes) which are separated by the PIV2 intron (grey box). The arrow describes the orientation of the sense strand from the PiALS exon 4.