Role of LEUNIG and LEUNIG_HOMOLOG in regulating early embryonic patterning in Arabidopsis

JF Golz1 and JE Lee2

  1. School of BioSciences, University of Melbourne, Royal Parade, Parkville, VIC 3010. Australia
  2. Umea Plant Science Centre, Department of Plant Physiology, Umea University, SE-901 87 Umea, Sweden

The closely related transcriptional regulators LEUNIG (LUG) and LEUNIG_HOMOLOG (LUH) are recruit to chromatin through interactions with the SEUSS (SEU) and SEU-LIKE (SLK) co-regulators and transcription factors. Work from our group and others has shown that the LUG regulatory complex plays diverse roles in Arabidopsis development including the regulation of leaf development and shoot apical meristem activity and the regulation of floral organ identity. Given the similarity in protein structure and expression profiles, it has been suggested that LUG and LUH might perform redundant functions. To explore this possibility, we generated lug luh double mutants and found that they display severe embryonic patterning defects. Furthermore, analysis of cell-type specific and auxin patterning markers reveal that apical-basal patterning and auxin localization are not correctly established during the early stages of lug luh embryo development. Moreover, finding similar defects in seu slk1 slk2 triple mutant embryos suggests that there is a high degree of redundancy between LUG/SEU/SLK and LUH/SEU/SLK complexes during embryogeneis. Genome-wide interactome studies have previous shown that SLK2 physically interacts with the WUSCHEL-RELATED HOMEOBOX9 (WOX9) transcription factor. We not only confirm this interaction, but show that other members of the SEU/SLK family interact with WOX9, as well as the closely related WOX8 protein. These interactions are highly significant, as previous work from several groups have shown that wox8 wox9 double mutant embryos display apical-basal patterning defects and thus suggest that the WOX transcription factors may be part of the LUG/LUH regulatory complex. We report our latest findings that support the existence of this complex in plants.