Dataset Information

Transcriptomic Effects of the Cell Cycle Regulator LGO in Arabidopsis Sepals.

ABSTRACT: Endoreduplication is a specialized cell cycle in which DNA replication occurs, but mitosis is skipped creating enlarged polyploid cells. Endoreduplication is associated with the differentiation of many specialized cell types. In the Arabidopsis thaliana sepal epidermis endoreduplicated giant cells form interspersed between smaller cells. Both the transcription factor Arabidopsis thaliana MERISTEM LAYER1 (ATML1) and the plant-specific cyclin dependent kinase inhibitor LOSS OF GIANT CELLS FROM ORGANS (LGO)/SIAMESE RELATED1 (SMR1) are required for the formation of giant cells. Overexpression of LGO is sufficient to produce sepals covered in highly endoreduplicated giant cells. Here we ask whether overexpression of LGO changes the transcriptome of these mature sepals. We show that overexpression of LGO in the epidermis (LGOoe) drives giant cell formation even in atml1 mutant sepals. Using RNA-seq we show that LGOoe has significant effects on the mature sepal transcriptome that are primarily ATML1-independent changes of gene activity. Genes activated by LGOoe, directly or indirectly, predominantly encode proteins involved in defense responses, including responses to wounding, insects (a predator of Arabidopsis), and fungus. They also encode components of the glucosinolate biosynthesis pathway, a key biochemical pathway in defense against herbivores. LGOoe-activated genes include previously known marker genes of systemic acquired resistance such as PR1 through PR5. The defensive functions promoted by LGOoe in sepals overlap with functions recently shown to be transcriptionally activated by hyperimmune cpr5 mutants in a LGO-dependent manner. Our findings show that the cell cycle regulator LGO can directly or indirectly drive specific states of gene expression; in particular, they are consistent with recent findings showing LGO to be necessary for transcriptional activation of many defense genes in Arabidopsis.

SUBMITTER: Schwarz EM

PROVIDER: S-EPMC5118908 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Transcriptomic Effects of the Cell Cycle Regulator LGO in Arabidopsis Sepals.

Schwarz Erich M EM Roeder Adrienne H K AH

Frontiers in plant science 20161122

Endoreduplication is a specialized cell cycle in which DNA replication occurs, but mitosis is skipped creating enlarged polyploid cells. Endoreduplication is associated with the differentiation of many specialized cell types. In the Arabidopsis thaliana sepal epidermis endoreduplicated giant cells form interspersed between smaller cells. Both the transcription factor Arabidopsis thaliana MERISTEM LAYER1 (ATML1) and the plant-specific cyclin dependent kinase inhibitor LOSS OF GIANT ...[more]

PMID: 27920789

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Project description:In all domains of life, proper regulation of the cell cycle is critical to coordinate genome replication, segregation and cell division. In some groups of bacteria, e.g. Alphaproteobacteria, tight regulation of the cell cycle is also necessary for the morphological and functional differentiation of cells. Sinorhizobium meliloti is an alphaproteobacterium that forms an economically and ecologically important nitrogen-fixing symbiosis with specific legume hosts. During this symbiosis S. meliloti undergoes an elaborate cellular differentiation within host root cells. The differentiation of S. meliloti results in massive amplification of the genome, cell branching and/or elongation, and loss of reproductive capacity. In Caulobacter crescentus, cellular differentiation is tightly linked to the cell cycle via the activity of the master regulator CtrA, and recent research in S. meliloti suggests that CtrA might also be key to cellular differentiation during symbiosis. However, the regulatory circuit driving cell cycle progression in S. meliloti is not well characterized in both the free-living and symbiotic state. Here, we investigated the regulation and function of CtrA in S. meliloti. We demonstrated that depletion of CtrA cause cell elongation, branching and genome amplification, similar to that observed in nitrogen-fixing bacteroids. We also showed that the cell cycle regulated proteolytic degradation of CtrA is essential in S. meliloti, suggesting a possible mechanism of CtrA depletion in differentiated bacteroids. Using a combination of ChIP-Seq and gene expression microarray analysis we found that although S. meliloti CtrA regulates similar processes as C. crescentus CtrA, it does so through different target genes. For example, our data suggest that CtrA does not control the expression of the Fts complex to control the timing of cell division during the cell cycle, but instead it negatively regulates the septum-inhibiting Min system. Our findings provide valuable insight into how highly conserved genetic networks can evolve, possibly to fit the diverse lifestyles of different bacteria.

Dataset Information

Transcriptomic Effects of the Cell Cycle Regulator LGO in Arabidopsis Sepals.

Publications

Transcriptomic Effects of the Cell Cycle Regulator LGO in <i>Arabidopsis</i> Sepals.

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