Genome-wide analysis of the SWEET gene family and its response to powdery mildew and leaf spot infection in the common oat (Avena sativa L.)

Abstract The yield and nutritional quality of oats are usually inhibited by plant diseases such as red leaf, powdery mildew, and leaf spot. SWEETs (Sugars Will Eventually be Exported Transporters) are a newly discovered type of sugar transporter that play important roles in regulating plant growth and development, the abiotic stress response, and the interactions between plants and pathogens. However, members of the SWEET gene family and their roles in responding to biotic stresses have not yet been characterized in oats (Avena sativa). In this study, 13 AsSWEET genes were identified, distributed across nine chromosomes in the oat genome. They all were predicted to contain seven transmembrane regions. Phylogenetic analysis showed that AsSWEET proteins clustered into four clades and possessed high homology with SWEET proteins in the family Poaceae. AsSWEET proteins were predicted to localize to the plasma membrane. The promoter regions of the oat AsSWEET genes contained cis-acting elements related to light response, growth and development, and stress response. Furthermore, the expression patterns of AsSWEET genes in two oat varieties, 'Yanwang' and 'Mulesi', were analyzed after powdery mildew and leaf spot infections. The relative expression levels of the majority of AsSWEET genes were significantly up-regulated or down-regulated after infection with pathogens, including AsSWEET1a, AsSWEET1b, AsSWEET2b, AsSWEET3a, AsSWEET11, and AsSWEET16. These SWEETs are potential candidate genes for the response to diseases in oats. In conclusion, this study provides a theoretical basis for future research into the regulatory mechanisms of the AsSWEETs, particularly their roles in the resistance to powdery mildew and leaf spot, and may promote further enhancements to the molecular breeding of the oat.