Characteristics of Paeonia ostii seed oil body and OLE17.5 determining oil body morphology

• Lipids of P. ostii seeds were stored in OBs. • P. ostii seed oil contained five dominant fatty acid compositions. • P. ostii seed oil yield and fatty acid content were in line with OB accumulation. • P. ostii OB stability was affected by NaCl concentration and pH value. • PoOLE17.5 was localized in OBs and regulated OB morphology and fatty acid content. Paeonia ostii is an emerging woody oil crop and cultivated on a large scale in China. This study attempted to characterize the characteristics of P. ostii seed oil body (OB) and found the key genes related to its morphology. The results showed that P. ostii seed oil contained five dominant fatty acid compositions that were stored in OBs. During the development of seeds, oil yield and fatty acid content were in line with OB accumulation. Moreover, NaCl concentration and pH value could influence P. ostii OB stability. Additionally, oleosins (OLEs) were identified as the most abundant proteins in OBs. Based on the expression levels of OLEs , PoOLE17.5 was isolated, which might be localized in OBs. And overexpression of PoOLE17.5 in tobacco obviously increased seed size and hundred-seed weight, altered OB morphology and increased fatty acid content. These results could provide a theoretical basis for improving oil yield of P. ostii seeds.