Cauliflower mosaic virus disease spectrum uncovers novel susceptibility factor NCED9 in Arabidopsis thaliana

Viruses are intimately linked with their hosts and especially dependent on gene-for-gene interactions to establish successful infections. The genotype of their hosts thus has a strong influence on the outcome virus disease. On the host side, defence mechanisms like tolerance and resistance can occur within the same species leading to differing virus accumulation in relation to symptomology and plant fitness. The identification of novel resistance genes and susceptibility factors against viruses is an important part in understanding viral pathogenesis and securing food production. The model plant Arabidopsis thaliana displays a wide symptom spectrum in response to RNA virus infections and unbiased genome-wide association studies have proven a powerful tool to identify novel disease-genes. In this study we infected natural accessions of Arabidopsis thaliana with the pararetrovirus Cauliflower mosaic virus to study the phenotypic variations between accessions and their correlation with virus accumulation. Through genome-wide association mapping of viral accumulation differences, we identified several susceptibility factors for CaMV, the strongest of which was the abscisic acid synthesis gene NCED9. Further experiments confirmed the importance of abscisic acid homeostasis and its disruption for CaMV disease.