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A bHLH-PAS protein regulates light-dependent rhythmic processes in the marine diatom Phaeodactylum tricornutum

TitleA bHLH-PAS protein regulates light-dependent rhythmic processes in the marine diatom Phaeodactylum tricornutum
Publication TypeJournal Article
Year of Publication2018
AuthorsAnnunziata R, Ritter A, Fortunato AEmidio, Cheminant-Navarro S, Agier N, Huysman MJJ, Winge P, Bones A, Bouget F-Y, Lagomarsino MCosentino, Bouly JPierre, Falciatore A
JournalbioRxiv
Pagination271445
KeywordsRCC2967
Abstract

Periodic light dark cycles govern the timing of basic biological processes in organisms inhabiting land as well as the sea, where life evolved. Although prominent marine phytoplanktonic organisms such as diatoms show robust diurnal rhythms in growth, cell cycle and gene expression, the molecular bases controlling these processes are still obscure. By exploring the regulatory landscape of diatom diurnal rhythms, we here unveil the key function of a Phaeodactylum tricornutum bHLH-PAS protein, named Pt bHLH1a, in the regulation of light-dependent rhythms. Peak expression of Pt bHLH1a mRNA occurs at the end of the light period and it is adjusted to photoperiod changes. Ectopic over-expression of Pt bHLH1a results in lines with altered cell division and gene expression and showing a phase shift in diurnal responses, compared to the wild-type cells. Reduced oscillations in gene expression are also observed in continuous darkness, showing that the regulation of rhythmicity by Pt bHLH1a is not directly dependent on light inputs and cell division. Pt bHLH1a orthologs are widespread in both pennate and centric diatom genomes, hinting at a common function in many species. This study adds new elements to understand diatom biology and ecology and offers new perspectives to elucidate timekeeping mechanisms in marine organisms belonging to a major, but still underinvestigated branch of the tree of life.

URLhttps://www.biorxiv.org/content/early/2018/02/25/271445
DOI10.1101/271445