DNA interactions of transcriptional co-regulator LEUNIG_HOMOLOG (LUH) during early stages of Arabidopsis flower development.

Transcriptional co-regulators are key modulators of gene expression, often functioning in complexes with transcription factors to regulate chromatin dynamics. LEUNIG_HOMOLOG (LUH) is a member of the conserved Groucho/Tup1 family of co-regulators in Arabidopsis, yet its role in flower development remains poorly understood. While LEUNIG (LUG), a homolog of LUH, has been extensively studied in floral organ identity specification, contributions of LUH appear to be both overlapping and distinct from LUG. Here, we investigate the LUH regulome, uncovering its dynamic protein interactions with transcriptional cofactors, histone-modifying enzymes, chromatin remodelers, and transcription factors, including MADS-domain proteins APETALA1 and SEPALLATA3. Using high-throughput DNA occupancy and transcriptomic analyses, we identify LUH target genes and their expression dynamics across floral developmental stages. Comparative transcriptome profiling of luh and lug mutants in floral induction system reveals unique regulatory functions of LUH. Furthermore, we provide some evidence for a dual role of LUH in transcriptional activation and repression. Our findings contribute to understanding how LUH modulates transcriptional responses and chromatin state to fine-tune flower development in Arabidopsis. Overall design: To study the high-throughput DNA occupancy of LUH protein at various stages of flower development, we conducted a series of chromatin immunoprecipitation followed by sequencing (ChIP-seq) experiments using the LUH-GFP in floral induction system (FIS) plant line (pLUH:LUH-GFP in pAP1:AP1-GR ap1 cal). We focused on four time points after the induction of flowering corresponding to: undifferentiated inflorescence meristem (0 days after induction, 0 DAI), meristem specification (2 DAI), organ specification (4 DAI), and organ differentiation (8 DAI). At least two biological replicates of each time point were prepared with the input samples as controls. We used GFP antibodies (#ab290, Abcam) for the immunoprecipitation.