title: Transcriptomic Effects of the Cell Cycle Regulator LGO inArabidopsisSepals.
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 theArabidopsis thalianasepal epidermis endoreduplicated giant cells form interspersed between smaller cells. Both the transcription factorArabidopsis thalianaMERISTEM 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 inatml1mutant sepals. Using RNA-seq we show thatLGOoehas significant effects on the mature sepal transcriptome that are primarily ATML1-independent changes of gene activity. Genes activated byLGOoe, directly or indirectly, predominantly encode proteins involved in defense responses, including responses to wounding, insects (a predator ofArabidopsis), 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 asPR1throughPR5. The defensive functions promoted byLGOoein sepals overlap with functions recently shown to be transcriptionally activated by hyperimmunecpr5mutants 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 inArabidopsis.
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca NY, USA.
authors.forename: Erich M
authors.initials: EM
authors.lastname: Schwarz
authors.affiliation: Weill Institute for Cell and Molecular Biology and Section of Plant Biology, School of Integrative Plant Sciences, Cornell University, Ithaca NY, USA.
authors.forename: Adrienne H K
authors.initials: AH
authors.lastname: Roeder
keywords: Arabidopsis thaliana; RNA-seq; endoreduplication; endoreplication; loss of giant cells from organs (lgo); sepal; siamese related1 (smr1); transcriptome