Mutant-based model of two independent pathways for carotenoid-mediated chloroplast biogenesis in Arabidopsis embryos.
- 1Institute of Biology and Ecology, Faculty of Science, Pavol Jozef Šafárik University in Košice, Slovakia
- 2Flanders Institute for Biotechnology, Belgium
Chloroplasts are essential for autonomous plant growth and their biogenesis is a complex process requiring both plastid and nuclear genome. One of the essential factors required for chloroplast biogenesis are carotenoids. Carotenoids are synthesized in plastids and it was shown that plastid localized methylerythritol 4-phosphate (MEP) pathway is responsible for providing substrates for their biosynthesis. Here we show, using results of our own mutant analysis combined with the results of others, that MEP-independent pathway, likely MVA-dependent pathway, provides intermediates for chloroplast biogenesis in Arabidopsis embryos. Pattern of this chloroplast biogenesis differs from the MEP-dependent chloroplast biogenesis. In MEP-dependent chloroplast biogenesis chloroplasts are formed rather uniformly in the whole embryo, with stronger chlorophyll accumulation in cotyledons. In MEP-independent pathway chloroplasts are formed predominantly in the hypocotyl and in the embryonic root. We also show that this pattern of chlorophyll accumulation is common to MEP pathway mutants as well as to the mutant lacking geranylgeranyl diphosphate synthase 11 (GGPPS11) activity in plastids but expressing it in the cytosol (GGPPS11cyt). It was recently described that shorter GGPPS11 transcripts are present in Arabidopsis and they can be translated into active cytosolic proteins. We therefore propose that MEP-independent pathway for chloroplast biogenesis in Arabidopsis embryos is MVA pathway that provides substrates for the synthesizes of GGPP via GGPPS11cyt and this is then transported to plastids, where it is used for carotenoid biosynthesis and subsequently for chloroplast biogenesis.
Keywords: GGPPS11, MEP pathway, CHLOROPLAST BIOGENESIS, mutants, isoprenoids, Arabidopis thaliana
Received: 20 May 2019;
Accepted: 24 Jul 2019.
Edited by:Li Li, Cornell University, United States
Reviewed by:Enrique Martinez Force, Spanish National Research Council (CSIC), Spain
Guodong Wang, Institute of Genetics and Developmental Biology (CAS), China
Copyright: © 2019 Vranova, Kopcsayova, Kosuth and Colinas. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Dr. Eva Vranova, Institute of Biology and Ecology, Faculty of Science, Pavol Jozef Šafárik University in Košice, Košice, Slovakia, email@example.com