The aureochrome photoreceptor PtAUREO1a is a highly effective blue light switch in diatoms

Abstract

Aureochromes represent a unique type of blue-light photoreceptors that possess a blue-light sensing flavin-binding LOV-domain and a DNA-binding bZIP domain, thus being light-driven transcription factors. The diatom Phaeodactylum tricornutum, a member of the essential marine primary producers, possesses four aureochromes (PtAUREO1a, 1b, 1c, 2). We here show a dramatic change in the global gene expression pattern of P. tricornutum wild type cells after a shift from red to blue light. About 75% of the genes show significantly changed transcript levels already after 10 and 60 min of blue light exposure, which includes genes of major transcription factors as well as other photoreceptors. Very surprisingly, in independent PtAureo1a knockout lines, this light-induced regulation of gene expression is almost completely inhibited. Such a massive and fast transcriptional change depending on one single photoreceptor is so far unprecedented. We conclude that PtAUREO1a plays a key role after shifts to blue light in diatoms.