NPR1 as a transgenic crop protection strategy in horticultural species

The NPR1(NONEXPRESSOR OF PATHOGENESIS RELATED GENES1)gene has a central role in the long-lasting,broad-spectrum defense response known as systemic acquired resistance(SAR).When overexpressed in a transgenic context in Arabidopsis thaliana,this gene enhances resistance to a number of biotic and abiotic stresses.Its position as a key regulator of defense across diverse plant species makes NPR1 a strong candidate gene for genetic engineering disease and stress tolerance into other crops.High-value horticultural crops face many new challenges from pests and pathogens,and their emergence exceeds the pace of traditional breeding,making the application of NPR1-based strategies potentially useful in fruit and vegetable crops.However,plants overexpressing NPR1 occasionally present detrimental morphological traits that make its application less attractive.The practical utility of NPR-based approaches will be a balance of resistance gains versus other losses.In this review,we summarize the progress on the understanding of NPR1-centered applications in horticultural and other crop plants.We also discuss the effect of the ectopic expression of the A.thaliana NPR1 gene and its orthologs in crop plants and outline the future challenges of using NPR1 in agricultural applications.

Evolution of the MLO gene families in octoploid strawberry(Fragaria×ananassa)and progenitor diploid species identified potential genes for strawberry powdery mildew resistance

Powdery mildew(PM)caused by Podosphaera aphanis is a major fungal disease of cultivated strawberry.Mildew Resistance Locus O(MLO)is a gene family described for having conserved seven-transmembrane domains.Induced loss-of-function in specific MLO genes can confer durable and broad resistance against PM pathogens.However,the genomic structure and potential role of MLO genes for PM resistance have not been characterized yet in the octoploid cultivated strawberry.In the present study,MLO gene families were characterized in four diploid progenitor species(Fragaria vesca,F.iinumae,F.viridis,and F.nipponica)and octoploid cultivated(Fragaria×ananassa)strawberry,and potential sources of MLO-mediated susceptibility were identified.Twenty MLO sequences were identified in F.vesca and 68 identified in F.×ananassa.Phylogenetic analysis divided diploid and octoploid strawberry MLO genes into eight different clades,in which three FveMLO(MLO10,MLO17,and MLO20)and their twelve orthologs of FaMLO were grouped together with functionally characterized MLO genes conferring PM susceptibility.Copy number variations revealed differences in MLO composition among homoeologous chromosomes,supporting the distinct origin of each subgenome during the evolution of octoploid strawberry.Dissecting genomic sequence and structural variations in candidate FaMLO genes revealed their potential role associated with genetic controls and functionality in strawberry against PM pathogen.Furthermore,the gene expression profiling and RNAi silencing of putative FaMLO genes in response to the pathogen indicate the function in PM resistance.These results are a critical first step in understanding the function of strawberry MLO genes and will facilitate further genetic studies of PM resistance in cultivated strawberry.

The strawberry genome:a complicated past and promising future

Within the juicy red flesh of the commercial strawberry lies a deep history that spans at least three continents and hundreds of thousands of years.The genetic heritage of this prized dessert fruit was crafted by nature,with its modern improvement driven by the indigenous Mapuche people of South America,a seafaring a French spy,and a plant-loving teenager that gathered fruits to present to a king.The many stories that punctuate the history of the modern strawberry relate to its contemporary cultivation as well as origins that span a significant portion of the globe1,2.