The early nitrogen starvation response o f the diatom Phaeodactylum
tric o rn u tu m
M atthijs M ic h ie i'23, Michele Fabris123, T. Obata4, Stefaan Broos56, Gino B a art'23, A.R. Fernie4,
Wim Vyverm an3 and Alain G oossens'2
' D epartm ent o f Plant Systems Biology, VIB, T echnologiepark 927, B-9052 Ghent, Belgium
E-mail: m im at@ psb.vib-uqent.be
2 D epartm ent o f Plant Biotechnology and Genetics, Ghent University, T echnologiepark 927,
B-9052 Ghent, Belgium
3 D epartm ent o f Biology, Ghent University, Krijgslaan 281, B-9000 Ghent, Belgium
4 Max Planck Institute o f M olecular Plant Physiology, W issenschaftspark Golm,
Am M ühlenberg 1, D-14476 Potsdam-Golm, Germany
5 D epartm ent fo r M olecular Biomedical Research, VIB, T echnologiepark 927, B-9052 Ghent, Belgium
6 D epartm ent o f Biomedical M olecular Biology, Ghent University, B-9052 Ghent, Belgium
In th is study we investigated the tra n scrip to m ic and m etabolic response o f Phaeodactylum
tric o rn u tu m to nitrogen starvation and o th e r stresses during the firs t 24 hours. P. tric o rn u tu m is a
unicellular marine alga o f the coastal zone. These algae live in a varied environm ent where n utrien t
and lig h t availab ility can fluctuate substantially. N itrogen starvation induces the accum ulation o f
lipids in algae which has potential biotechnological purposes. The aim o f the study was to find
tran scrip tion al regulators th a t coordinate th is process.
Using RNA-seq, we sequenced a to ta l o fte n points across the d iffe re n t tim e p o in ts and conditions.
The response in the prim ary m etabolism was found to be dram atically d iffe re n t when com pared to
nitrogen starvation in green algae. The c itric acid cycle especially was under tig h t tran scrip tion al
co ntrol and likely plays a central role in the repurposing o f carbon and nitrogen in the cell. To
investigate th is fu rth e r m etabolic labeling experim ents are being perform ed.
A d ditio na lly, in the p rom otors o f genes upregulated during nitrogen starvation several
overrepresented m otifs were found. By em ploying a Yeast One Hybrid screen, a pote ntia lly novel
tran scrip tio n fa cto r term ed NMB1 was found. NMB1 was previously unannotated but appears
evolutionary conserved in the heterokontae. P. tric o rn u tu m contains tw o o the r m em bers o f this
gene fam ily. The expression profiles o f tw o o ut o f three putative tra n scrip tio n factors cluster
to g e th e r w ith a substantial part o f the nitrogen salvaging and am ino acid breakdown genes,
im plying a fu n ctio n a l link w ith the ta rg et process. NMB1 would be the firs t tra n scrip tio n factor
known to be involved in n u trie n t responses in diatom s.
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