Project description:In this study, we have characterized a putative chloroplast ribosome assembly factor. To elucidate transcriptional responses caused by decreased chloroplast function, we have measured the transcriptome of wild-type and knock-down seedlings.
Project description:The transition of chloroplast function from biogenesis to degeneration upon leaf senescence is critical for a plant’s fitness, as nutrient relocation from leaves to reproductive organs is achieved through this process. The optimal timing of transition should be regulated by tight coordination between chloroplast and nucleus, but the underlying mechanisms remain elusive. Here, we describe the regulatory mechanism of this transition. Chloroplast-Related LONG NONCODING RNA 1 (CHLORELLA1) is highly co-expressed with genes coding for chloroplast functionality during leaf development. Leaves of chlorella exhibit precocious senescence symptoms and a decline in the expression of chloroplast-associated genes, indicating that CHLORELLA1 plays a role in maintaining chloroplast function. Mechanistically, nucleus-encoded CHLORELLA1 transcripts are translocated into the chloroplast and contribute to the assembly of the plastid-encoded RNA polymerase (PEP) complex. At aged leaves, decreased expression of CHLORELLA1 attenuates PEP complex assembly and transcription of photosynthesis genes, possibly triggering leaf senescence. Moreover, CHLORELLA1 is directly activated by GLK1/2, master regulators of chloroplast maintenance. Our study unravels a new layer of the regulation via chloroplast-targeted lncRNA as an anterograde signal in timely decision of leaf senescence.
Project description:Chloroplast biogenesis represents a crucial step in seedling development, and is essential for the transition to autotrophic growth in plants. This light-controlled process relies on the transcription of nuclear and plastid genomes that drives the effective assembly and regulation of the photosynthetic machinery. Here we reveal a novel regulation level for this process by showing the involvement of chromatin remodelling in the coordination of nuclear and plastid gene expression for proper chloroplast biogenesis and function. The two Arabidopsis homologs of the yeast EPL1 proteins, core components of the NuA4 histone acetyl-transferase complex, are essential for the correct assembly and performance of chloroplasts. EPL1 proteins are necessary for the coordinated expression of nuclear genes encoding most of the components of chloroplast transcriptional machinery, specifically promoting H4K5Ac deposition in these loci. These data unveil a key participation of epigenetic regulatory mechanisms in the coordinated expression of the nuclear and plastid genomes.