Anthocyanin can improve the survival of rice seeds from solar light outside the international space station

A purple-pigmented (purple) rice seeds containing an anthocyanin, a major class of flavonoids, and their isogenic non-pigmented (white) seeds were exposed outside of the international space station (ISS) to evaluate the impact of anthocyanin on seed viability in space. The rice seeds were placed in sample plates at the exposed facility of ISS for 440 days, with the bottom layer seeds exposed to space radiation and the top layer seeds exposed to both solar light and space radiation. Though the seed weight of both purple and white seeds decreased after exposure to outer space, growth percentages after germination of purple and white seeds in the top layer were 55 and 15 %, respectively, compared to those in the bottom layer 100 and 70 %, respectively. RNA analysis revealed that 1,590 and 1,546 seed-stored mRNAs (long-lived mRNAs) were degraded in the white seeds of the top and the bottom layers, respectively, whereas those of the purple seeds in the top and bottom layers were 548 and 303, respectively. These results suggest that anthocyanin protected seeds and safeguarded long-lived mRNAs from solar light and space radiation to increase the seed viability.