Chloroplast Dysfunction Causes Multiple Defects in Cell Cycle Progression in the Arabidopsis crumpled leaf Mutant    

Abstract

The majority of research on cell cycle regulation is focused on the nuclear events that govern the replication and segregation of the genome between the two daughter cells. However, eukaryotic cells contain several compartmentalized organelles with specialized functions, and coordination among these organelles is required for proper cell cycle progression, as evidenced by the isolation of several mutants in which both organelle function and overall plant development were affected. To investigate how chloroplast dysfunction affects the cell cycle, we analyzed the crumpled leaf (crl) mutant of Arabidopsis (Arabidopsis thaliana), which is deficient for a chloroplastic protein and displays particularly severe developmental defects. In the crl mutant, we reveal that cell cycle regulation is altered drastically and that meristematic cells prematurely enter differentiation, leading to reduced plant stature and early endoreduplication in the leaves. This response is due to the repression of several key cell cycle regulators as well as constitutive activation of stress-response genes, among them the cell cycle inhibitor SIAMESE-RELATED5. One unique feature of the crl mutant is that it produces aplastidic cells in several organs, including the root tip. By investigating the consequence of the absence of plastids on cell cycle progression, we showed that nuclear DNA replication occurs in aplastidic cells in the root tip, which opens future research prospects regarding the dialogue between plastids and the nucleus during cell cycle regulation in higher plants.

Role of pyrimidine salvage pathway in the maintenance of organellar and nuclear genome integrity

“…Here, we found that sog1 is hypersensitive to genotoxins targeting organelle DNA, suggesting that retrograde signalling pathways are activated by chloroplast DNA damage to trigger SOG1 activity. Indeed, it has been shown previously that ROS production in organelles activates ATM and the DDR pathway (Yi et al, 2014), and that chloroplast dysfunction induces the expression of SOG1 target genes (Hudik et al, 2014), some of which could be involved in the protection or repair of organelle genomes. A plethora of retrograde signalling routes have been described (de Souza et al, 2017), however, and further studies will be needed to determine how they are connected to the DDR.…”

Transcript level coordination of carbon pathways during silicon starvation‐induced lipid accumulation in the diatom Thalassiosira pseudonana

“…Cellular growth and chloroplast replication are tightly regulated cellular processes (Wittenberg & Reed, 2005; Hudik et al ., 2014) and are shown to be coordinated in diatoms (Gillard et al ., 2008). A strong transcript level response at 4 h of silicon starvation was documented in T. pseudonana and occurred while nearly half of the population continued to progress through the cell cycle (Fig.…”

MOS1 functions closely with TCP transcription factors to modulate immunity and cell cycle in Arabidopsis

“…To identify the cell-cycle phase affected by MOS1, we analyzed the expression of five cell-cycle genes that have expression in specific cell-cycle phases in mos1. CDT1 and MCM2 are both associated with the G1/S transition and early S-phase; CYCD3;1 is predominantly at the G1/S transition; PCNA1 is expressed throughout S-phase; and CDC20.1 is expressed at the G2/M transition (Menges et al, 2002;Kevei et al, 2011;Hudik et al, 2014). We chose the fifth true leaf from plants whose eighth and ninth true leaves just became visible, so that the selected leaves were at a comparable developmental stage.…”