Edited by Ulf-Ingo FlüggeKeywords: Chloroplast Development Embryo Mitochondrion Phosphatidylglycerol Phospholipid a b s t r a c t Phosphatidylglycerophosphate (PGP) synthase, encoded by PGP1 and PGP2 in Arabidopsis, catalyzes a committed step in the biosynthesis of phosphatidylglycerol (PG). In this study, we isolated a pgp1pgp2 double mutant of Arabidopsis to study the function of PG. In this mutant, embryo development was delayed and the majority of seeds did not germinate. Thylakoid membranes did not develop in plastids, mitochondrial membrane structures were abnormal in the mutant embryos, and radiolabeling of phospholipids showed that radioactivity was not significantly incorporated into PG. These results demonstrated that PG biosynthesis is essential for the development of embryos and normal membrane structures of chloroplasts and mitochondria.
Chloroplast biogenesis involves the coordinated expression of the plastid and nuclear genomes, requiring information to be sent from the nucleus to the developing chloroplasts and vice versa. Although it is well known how the nucleus controls chloroplast development, it is still poorly understood how the plastid communicates with the nucleus. Currently, haem is proposed as a plastid-to-nucleus (retrograde) signal that is involved in various physiological regulations, such as photosynthesis-associated nuclear genes expression and cell cycle in plants and algae. However, components that transduce haem-dependent signalling are still unidentified. In this study, by using haem-immobilized high-performance affinity beads, we performed proteomic analysis of haem-binding proteins from
Arabidopsis thaliana
and
Cyanidioschyzon merolae
. Most of the identified proteins were non-canonical haemoproteins localized in various organelles. Interestingly, half of the identified proteins were nucleus proteins, some of them have a similar function or localization in either or both organisms. Following biochemical analysis of selective proteins demonstrated haem binding. This study firstly demonstrates that nucleus proteins in plant and algae show haem-binding properties.
This article is part of the theme issue ‘Retrograde signalling from endosymbiotic organelles’.
Previous studies showed that at least two transcription factors, HY5 and GLK2, were involved in the coexpression network of key chlorophyll and photosynthesis genes, but they were not sufficient for fully functional photosystem assembly. To explore the transcriptional mechanism, here genes encoding nuclear transcription factors were identified, which were induced in greenish roots of Arabidopsis. Further expression analysis suggested that the expression of these factors was independent from HY5-and GLK-dependent signaling pathways. To clarify the gene expression network, further analysis of such transcription factors involved in chloroplast differentiation will be necessary.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.