BnaPPT1 is essential for chloroplast development and seed oil accumulation in Brassica napus

INTRODUCTION: Phosphoenolpyruvate/phosphate translocator (PPT) transports phosphoenolpyruvate from the cytosol into the plastid for fatty acid (FA) and other metabolites biosynthesis. OBJECTIVES: This study investigated PPTs’ functions in plant growth and seed oil biosynthesis in oilseed crop Brassica napus. METHODS: We created over-expression and mutant material of BnaPPT1. The plant development, oil content, lipids, metabolites and ultrastructure of seeds were compared to evaluate the gene function. RESULTS: The plastid membrane localized BnaPPT1 was found to be required for normal growth of B. napus. The plants grew slower with yellowish leaves in BnaA08.PPT1 and BnaC08.PPT1 double mutant plants. The results of chloroplast ultrastructural observation and lipid analysis show that BnaPPT1 plays an essential role in membrane lipid synthesis and chloroplast development in leaves, thereby affecting photosynthesis. Moreover, the analysis of primary metabolites and lipids in developing seeds showed that BnaPPT1 could impact seed glycolytic metabolism and lipid level. Knockout of BnaA08.PPT1 and BnaC08.PPT1 resulted in decreasing of the seed oil content by 2.2 to 9.1%, while overexpression of BnaC08.PPT1 significantly promoted the seed oil content by 2.1 to 3.3%. CONCLUSION: Our results suggest that BnaPPT1 is necessary for plant chloroplast development, and it plays an important role in maintaining plant growth and promoting seed oil accumulation in B. napus.