LAUSR

Description The expression of phased small interfering RNAs caused monkeyflower color evolution Pigmentation in flower petals mainly relies on anthocyanins and carotenoids, two classes of pigments whose biosynthetic and regulatory pathways are well characterized (1) and constitute theoretically ideal targets for evolution to create new color patterns. However, evolution of flower color sometimes works in mysterious ways. On page 576 of this issue, Liang et al. (2) show that a major speciation locus in Mimulus (monkeyflowers) that causes change in flower color contains a noncoding inverted repeat region. This repeat produces a long noncoding RNA that is cleaved into small interfering RNAs (siRNAs) in a regularly spaced (“phased”) pattern, and some of these siRNAs regulate the translation of a carotenoid biosynthesis regulator. The finding that flower color change was caused by an inverted repeat that produces phased siRNAs constitutes an unexpected molecular mechanism for flower morphological evolution.