What a difference a base makes: A single nucleotide confers Alternaria resistance in apple ($) (Plant Cell)

Golden Delicious apples are particularly susceptible to the fungal pathogen Alternaria alternaria f. sp. mali. Zhang et al. have traced this susceptibility to a single nucleotide in the promoter of gene encoding a hairpin RNA (hpRNA), MdhpRNA277. This hpRNA produces small RNAs that selectivey target five resistance genes. In susceptible plants, the hpRNA is produced and R genes silenced. In resistant plants, the single-nucleotide polymorphism disrupts binding of a transcription factor and so expression of the hpRNA, allowing high-level expression of the targeted R genes, and resistance to the fungus. As the authors report, “The ability to identify apple lines that are resistant to this devastating disease makes this SNP a valuable tool for the apple breeding industry.” (Summary by Mary Williams) Plant Cell 10.1105/tpc.18.00042