Biology subjects

Boussardon, C.

Publications and source records attributed to Boussardon, C..

4 recordsLinked to original sources

bioRxiv2024

GCS-H2 is essential for growth as it acts as the main relay for mitochondrial lipoylation in heterotrophic tissues of Arabidopsis thaliana

H-protein is part of the multi-protein glycine cleavage system found in both prokaryotes and eukaryotes. The Arabidopsis thaliana genome contains three loci for genes encoding H-protein. We show that in land plants, there are two clades of mitochondrial H-proteins; one that clusters with H1 and H3, and another that clusters with H2, an isoform mostly expressed in heterotrophic tissue and for which a null mutation results in a >99% impeded growth. After showing that all three isoforms fulfill the same metabolic function, we evidenced that the impaired root growth in h2 results from an altered cell cycle progression concomitant to a lower Target Of Rapamycin kinase activity. Subsequent metabolomic approaches revealed an accumulation of storage sugars and a significant decrease of the TCA intermediates and several vitamins in the h2 root cells as compared to the wild-type ones. Additional investigations evidenced that H2 acts as the main relay for lipoylation in root mitochondria, which diverges from the current lipoylation model proposed for photosynthetic tissues. Together, this work provides new insight on the control of the cell cycle by mitochondrial metabolism, and also challenges the current dogma for lipoylation in mitochondria of plant cells. Once sentence summaryThe absence of GCS-H2, an isoform of H-protein found in heterotrophic tissue, impedes the cell cycle, and drastically affects plant growth as it acts as the main relay for mitochondrial lipoylation.

plant biology↗

bioRxiv2024

The unusual orf117Sha locus causes desynchronization of pollen development in the Arabidopsis gametophytic Sha CMS

Cytoplasmic male sterility (CMS) is of major agronomical relevance in hybrid breeding. In gametophytic CMS, abortion of pollen is determined by the grain genotype, while in sporophytic CMS, it is determined by the mother plant genotype. While several CMS mechanisms have been dissected at the molecular level, gametophytic CMS has not been straightforwardly accessible. We used the gametophytic Sha-CMS in Arabidopsis to characterize the cause and process of pollen abortion by implementing in vivo biosensing in single pollen and mitoTALEN mutagenesis. We obtained conclusive evidence that orf117Sha is the CMS-causing gene, despite distinct characteristics from other CMS-genes. We measured the in vivo cytosolic ATP content in single pollen, followed pollen development and analyzed pollen mitochondrial volume in two genotypes that differed only by the presence of the orf117Sha locus. Our results show that the Sha-CMS is not triggered by ATP deficiency. Instead, we observed desynchronization of a pollen developmental program. Pollen death occurred independently in pollen grains at diverse stages and was preceded by mitochondrial swelling. We conclude that pollen death is grain-autonomous in Sha-CMS and propose that mitochondrial permeability transition, which was previously described as a hallmark of developmental and environmental-triggered cell death programs, precedes pollen death in Sha-CMS. HighlightThe Arabidopsis CMS-causing gene orf117Sha does not limit pollen ATP supply. Pollen-centered approaches show desynchronization of development and mitochondrial swelling before pollen death, which occurred at diverse stages.

plant biology↗

bioRxiv2022

The mitochondrial ferredoxin-like is essential for the formation of complex I-containing respiratory supercomplexes in Arabidopsis thaliana

In eukaryotes, mitochondrial ATP is mainly produced by the oxidative phosphorylation (OXPHOS) system, which is composed of five multiprotein complexes (complexes I to V). Analyses of the OXPHOS system by native gel electrophoresis revealed an organization of OXPHOS complexes in supercomplexes, but their roles and assembly pathways remain unclear. In this study, we characterized an atypical mitochondrial ferredoxin (mFDX-like). This protein was previously found associated with complex I, being part of the bridge domain linking the matrix and membrane arms of the complex. A phylogenetic analysis suggests that the Arabidopsis thaliana mFDX-like evolved from classical mitochondrial ferredoxin, but it lost one of the cysteines required for the coordination of the iron-sulfur (Fe-S) cluster essential for the electron transfer function of ferredoxins. Accordingly, our biochemical study shows that AtmFDX-like does not bind an Fe-S cluster, and is therefore unlikely to be involved in electron transfer reactions. To study the function of mFDX-like, we created deletion lines in Arabidopsis using a CRISPR/Cas9 approach. These lines do not show any growth phenotype under standard growth condition. However, the characterization of the OXPHOS system demonstrates that mFDX-like is important for the assembly of complex I, and essential for the formation of complex I-containing supercomplexes. We propose that mFDX-like and the bridge domain are required for the correct conformation of the membrane arm of complex I that is essential for the association of complex I with complex III to form supercomplexes.

plant biology↗

bioRxiv2018

Novel cytonuclear combinations modify Arabidopsis seed physiology and vigor

The influence of intraspecific variation in cytoplasmic genomes and cytonuclear interactions on key seed traits that can impact adaptation and agriculture has not been thoroughly explored, so far. Here, dormancy, germination performance and longevity of seeds have been assessed in Arabidopsis plants with novel cytonuclear combinations that disrupt coadaptation between natural variants of nuclear and cytoplasmic genomes. Although all three traits were affected by cytonuclear reshuffling, the sensitivity of seed traits to cytoplasmic change was dependent on the nuclear background. Both deleterious and, more surprisingly, favorable effects of novel cytonuclear combinations (in comparison with the nuclear parent) were observed, suggesting suboptimal genetic combinations exist in natural populations for these traits. Significant changes on dormancy and germination performance due to specific cytonuclear interacting combinations mainly occurred in opposite directions, in accordance with the previously proposed dormancy continuum. Consistently, reduced sensitivity to exogenous ABA and faster endogenous ABA decay during germination were observed in a novel cytonuclear combination that also exhibited enhanced longevity and better germination performance, compared to its natural nuclear parent. Cytoplasmic genomes, therefore, represent an additional resource of natural variation for breeding seed vigor traits.\n\nIssue sectionGrowth and development\n\nHighlightNatural variation in Arabidopsis organelles and cytonuclear interactions influence seed dormancy, longevity and germination performance. Enhanced seed vigor was obtained through the creation of novel cytonuclear combinations.

plant biology↗