Plants need their vitamins too

Over recent years, the pathways for the biosynthesis of many vitamins have been elucidated at the molecular level in plants, and several unique features are emerging. One is that the mitochondrion plays an important role in the synthesis of folate (vitamin B-9), biotin (BA pantothenate (B-5), ascorbate (C), and possibly thiamin (B-1). Second, the production of some of these cofactors is regulated by developmental cues, and perhaps more surprisingly, by environmental signals such as high light and salinity. Moreover, the biosynthesis of thiamin in Arabidopsis may be negatively regulated by a riboswitch, a novel method of gene regulation that is characteristic of cofactor biosynthesis in bacteria. Vitamin B-12 is unique in that it is not found in vascular plants, but is abundant in algae; recent molecular work has revealed that algae do not synthesise the vitamin but instead obtain it from bacteria.