SEPALLATA

SEPALLATA
Name	SEPALLATA
Organism	Plantae
Taxid	3702
Locussymbol	SEP
Synonyms	SEPALLATA-like

SEPALLATA

SEPALLATA refers to a group of closely related plant homeotic genes first characterized in Arabidopsis thaliana and subsequently studied across flowering plants including Oryza sativa, Zea mays, and Petunia hybrida. The SEPALLATA genes encode MADS-box transcription factors that interact with other MADS proteins described in models such as the ABC model and later extensions including the ABCE model and the quartet model of floral organ identity. Research on SEPALLATA genes has been conducted by groups at institutions including the Max Planck Society, John Innes Centre, and Cold Spring Harbor Laboratory and published in journals such as Nature and The Plant Cell.

Introduction

SEPALLATA genes were defined through genetic screens in Arabidopsis thaliana that identified homeotic mutants affecting petal, stamen, and carpel identity, with foundational work by researchers from Development (journal), Plant Physiology (journal), and laboratories led by Elliot M. Meyerowitz and Enrico Coen. The SEP proteins belong to the MADS-box family first characterized in Saccharomyces cerevisiae and later linked to plant development through comparisons with MADS genes in Antirrhinum majus and Petunia inflata. Major conferences where SEPALLATA research was presented include meetings of the Society for Developmental Biology and the International Botanical Congress.

Gene Family and Nomenclature

The SEPALLATA family in Arabidopsis thaliana comprises SEP1, SEP2, SEP3, and SEP4, named in seminal papers from groups affiliated with University of California, Davis, Tsinghua University, and University of Cambridge. Homologs are denoted differently in grasses such as Oryza sativa (OsMADS) and in legumes like Medicago truncatula, reflecting nomenclature conventions from databases managed by The Arabidopsis Information Resource and the Gramene project. Phylogenetic analyses published by teams at ETH Zurich and University of California, Berkeley compare SEP sequences to clades described for AGAMOUS, PISTILLATA, APETALA1, and APETALA3.

Molecular Function and Protein Structure

SEP proteins contain the conserved MADS (M), intervening (I), keratin-like (K), and C-terminal (C) domains characteristic of MIKC-type transcription factors; structural studies and domain mapping have been reported by research groups at Harvard University and Massachusetts Institute of Technology. SEP proteins form higher-order complexes with proteins such as AGAMOUS and PISTILLATA via coiled-coil interactions in the K domain, a mechanism elucidated in work from EMBL and structural efforts using techniques from European Synchrotron Radiation Facility and Cold Spring Harbor Laboratory. Post-translational modifications and protein stability involving pathways studied at Max Planck Institute for Plant Breeding Research influence SEP activity and interaction with chromatin remodelers like SWI/SNF complex members characterized at Johns Hopkins University.

Role in Floral Development and ABC Model

SEP proteins act as E-class factors in the ABC model and are essential for specifying petal, stamen, and carpel identity in combination with A-, B-, and C-class proteins such as APETALA1, APETALA3, and AGAMOUS. Functional integration of SEP proteins into the quartet model explains organ specification demonstrated in studies from University of Oxford, University of Tokyo, and University of California, Los Angeles. Genetic and biochemical data from laboratories including Salk Institute and Max Planck Institute for Developmental Biology show that SEP paralogs provide redundancy and combinatorial specificity necessary for floral organogenesis described in reviews in Science and Trends in Plant Science.

Evolution and Comparative Genomics

Comparative genomics across angiosperms from projects hosted by Joint Genome Institute and Ensembl Plants reveal SEP gene duplication events correlated with whole-genome duplications documented in lineages such as Brassicaceae, Poaceae, and Solanaceae. Evolutionary studies by teams at University of Zurich, Kew Gardens, and University of Montpellier trace conserved C-terminal motifs and lineage-specific diversifications similar to patterns seen in MADS-box subfamilies including AGAMOUS-like genes. Fossil-calibrated phylogenies and molecular clock analyses published by researchers at University of Chicago and University of Geneva link SEP diversification to the rapid radiation of flowering plants discussed in works in PNAS and New Phytologist.

Expression Patterns and Regulation

SEP genes show spatial and temporal expression in floral meristems, sepals, petals, stamens, and carpels, as demonstrated by in situ hybridization and reporter gene studies from John Innes Centre, University of Edinburgh, and Nagoya University. Regulation involves transcription factors such as LEAFY, WUSCHEL, and AGAMOUS feedback loops described in studies from Cold Spring Harbor Laboratory and University of California, San Diego, as well as epigenetic control by Polycomb group proteins characterized at European Molecular Biology Laboratory. Hormonal influences from auxin and signal transduction pathways studied at Max Planck Institute modulate SEP expression during floral organ initiation reported in The Plant Cell.

Mutant Phenotypes and Functional Studies

Loss-of-function sep1 sep2 sep3 triple mutants in Arabidopsis thaliana transform petals, stamens, and carpels into sepaloid organs, phenotypes first characterized in landmark papers from Stanford University and Yale University. Overexpression and complementation experiments across species including Oryza sativa, Petunia hybrida, and Nicotiana benthamiana performed by groups at CNRS and RIKEN reveal conserved and divergent functions; CRISPR-Cas9 studies in laboratories at University of California, Berkeley and Wageningen University further refine functional domains. Protein–protein interaction assays such as yeast two-hybrid and co-immunoprecipitation used by teams at Max Planck Institute for Molecular Plant Physiology and Salk Institute corroborate quartet formation and target gene regulation implicated in developmental phenotypes reported in Developmental Cell.

Category:MADS-box genes