Plastochromanol-8 and tocopherols are essential lipid-soluble antioxidants during seed desiccation and quiescence in <i>Arabidopsis</i>

Abstract

Given their essential role as vitamin E, tocopherols and tocotrienols have been studied extensively in animals and plants. In contrast, our understanding of the function of plastochromanol-8 (PC-8), a third type of tocochromanol with a longer side chain, is very limited despite the wide distribution of PC-8 in the plant kingdom, including species consumed by humans. To investigate PC-8 function in vivo, we combined the Arabidopsis vte1 mutation that eliminates tocopherols and PC-8 and causes the accumulation of 2,3-dimethyl-6-phytyl-1,4-benzoquinol (DMPBQ), a redox-active tocopherol precursor, and the vte2 mutation that eliminates tocopherols without affecting PC-8. The vte2 vte1 double mutant lacks tocopherols, PC-8, and DMPBQ, and exhibits the most severe physiological and biochemical phenotypes of any tocochromanol-affected genotype isolated to date, most notably a severe seedling developmental phenotype associated with massive lipid oxidation initiated during seed desiccation and amplified during seed quiescence. In contrast, the presence of PC-8 in vte2 suppresses or attenuates all of the developmental and biochemical phenotypes observed in vte2 vte1, demonstrating that PC-8 is a lipid antioxidant in vivo. Finally, the low relative fitness of vte2 vte1 demonstrates that tocopherols and PC-8 are in vivo lipid antioxidants essential for seed plant survival.