Alterations of flower fertility, plant size, seed weight, and seed oil content in transgenic Camelina sativa plants overexpressing CYP78A

Abstract

Camelina (Camelina sativa (L.) Crantz) is an orphan oil crop with high potential for yield improvement through breeding and biotechnological approaches. Seed size and oil content of camelina are particularly low compared with high-yielding oil crops such as rapeseed (Brassica napus L.). The CYP78A genes of the P450 monooxygenase family were previously demonstrated to be involved in regulating seed development in arabidopsis (Arabidopsis thaliana L.). Here, we show that expression of three arabidopsis genes, AtCYP78A5, AtCYP78A6 or AtCYP78A9 under control of the CaMV35S promoter caused enhanced growth of transgenic camelina plants with larger silicles and larger seeds. The phenotype of the camelina lines strongly depended on the expressed AtCYP78A paralog and on the level of transgene expression. Excess overexpression of AtCYP78A6 or AtCYP78A9 resulted in very large seeds, a decrease in total seed weight per plant and infertility of flowers at the lower sections of the stems. Plants with lower expression levels showed moderately increased seed weights, especially AtCYP78A5 lines, with elevated oil and protein contents per seed weight compared to the wild type. The increases in seed weight and plant height were correlated with higher expression levels of the transgenes. Slight but significant reductions in seed weight were observed for plants with downregulation of CsCYP78A9 expression by RNAi accompanied with an increase in the oil content per seed weight. These results show that CYP78A genes regulate the seed development in camelina, and that excess expression affects fertility, while moderate expression provides a powerful strategy for manipulating plant biomass and seed traits in camelina.