Rice folate enhancement through metabolic engineering has an impact on rice seed metabolism, but does not affect the expression of the endogenous folate biosynthesis genes

Folates are key-players in one-carbon metabolism in all organisms. However, only micro-organisms and plants are able to synthesize folates de novo and humans rely entirely on their diet as a sole folate source. As a consequence, folate deficiency is a global problem. Although different strategies are currently implemented to fight folate deficiency, up until now, all of them have their own drawbacks. As an alternative and complementary means to those classical strategies, folate biofortification of rice by metabolic engineering was successfully achieved a couple of years ago. To gain more insight into folate biosynthesis regulation and the effect of folate enhancement on general rice seed metabolism, a transcriptomic study was conducted in developing transgenic rice seeds, overexpressing 2 genes of the folate biosynthetic pathway. Upon folate enhancement, the expression of 235 genes was significantly altered. Here, we show that rice folate biofortification has an important effect on folate dependent, seed developmental and plant stress response/defense processes, but does not affect the expression of the endogenous folate biosynthesis genes.