Change in gene expression in Chlamydomonas reinhardtii upon feeding with hemin and Mg-protoporphyrin

ABSTRACT: The tetrapyrroles Mg-protoporphyrin IX (MgProto) and heme, in Chlamydomonas reinhardtii only synthesized within the chloroplast, have been implicated in retrograde control of nuclear gene expression in this unicellular green alga. However, feeding of the two tetrapyrroles to Chlamydomonas cultures growing in the dark has previously been shown to transiently induce 5 nuclear genes, among them three genes coding for the chloroplast heat shock proteins HSP70A, B and E. Here, we measured the impact of MgProto and hemin feeding in the dark on changes in gene expression at the genomic level. About 10% of the 10000 genes represented on the microarray showed a transient up or down regulation with a fold change of 4 or more (p ≤0.05). The two most prominent groups of regulated genes were those where both MgProto and heme caused either an up or down regulation. Minor regulatory groups consisted of genes which were either down- or up-regulated by one of the tetrapyrroles but not by the other. In contrast, feeding of protoporphyrin IX had no regulatory effect on a number of selected genes. Interestingly, 499 of the 982 responding genes were also regulated by heat shock; 85% of those showed the same response (up or down) as seen after MgProto/heme feeding, indicating a previously not anticipated role of MgProto and heme in stress response. Indeed, most prominent among the functional groups of annotated genes up or down regulated by the tetrapyrroles were those whose gene products are involved in protein folding and/or protein degradation. Striking is the virtual absence of regulated genes that encode constituents of the photosynthetic apparatus. This and the transient nature of changes in gene expression observed upon feeding of the tetrapyrroles suggest a signaling role of these plastid compounds in the adaptation of the alga to alterations in the environment.

ORGANISM(S): Chlamydomonas reinhardtii

PROVIDER: GSE20860 | GEO | 2011/03/02

SECONDARY ACCESSION(S): PRJNA129625

REPOSITORIES: GEO