RT Journal Article
SR Electronic
T1 GUN1 regulates tetrapyrrole biosynthesis
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 532036
DO 10.1101/532036
A1 Takayuki Shimizu
A1 Nobuyoshi Mochizuki
A1 Akira Nagatani
A1 Satoru Watanabe
A1 Tomohiro Shimada
A1 Kan Tanaka
A1 Yuuki Hayashi
A1 Munehito Arai
A1 Sylwia M. Kacprzak
A1 Dario Leister
A1 Haruko Okamoto
A1 Matthew J. Terry
A1 Tatsuru Masuda
YR 2019
UL http://biorxiv.org/content/early/2019/01/28/532036.abstract
AB The biogenesis of the photosynthetic apparatus in developing chloroplasts requires the assembly of proteins encoded on both nuclear and chloroplast genomes1. To co-ordinate this process there needs to be communication between these organelles, and while we have a good understanding of how the nucleus controls chloroplast development, how the chloroplast communicates with the nucleus at this time is still essentially unknown2. What we do know comes from pioneering work in which a series of genomes uncoupled (gun) mutants were identified that show elevated nuclear gene expression after chloroplast damage3. Of the six reported gun mutations, five are in tetrapyrrole biosynthesis proteins4-6 and this has led to the development of a model for chloroplast-to-nucleus retrograde signaling in which ferrochelatase 1 (FC1)-dependent heme synthesis generates a positive signal promoting expression of photosynthesis-related genes6. However, the molecular consequences of the strongest of the gun mutants, gun17, is unknown, preventing the development of a unifying hypothesis for chloroplast-to-nucleus signaling. Here, we show that GUN1 directly binds to heme and other metal-porphyrins, affects flux through the tetrapyrrole biosynthesis pathway and can increase the chelatase activity of FC1. These results raise the possibility that the signaling role of GUN1 may be manifested through changes in tetrapyrrole metabolism and supports a role for tetrapyrroles as mediators of a single biogenic chloroplast-to-nucleus retrograde signaling pathway.