Role of MADS-box TFs in the seed coat of Arabidopsis thaliana

DR David1,2, NU Jayawardana1,2, MS Doblin1,2, A Bacic2 and JF Golz1

  1. School of BioSciences, The University of Melbourne, Parkville, Vic 3010. Australia
  2. ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, The University of Melbourne, Parkville, Vic 3010. Australia

During Arabidopsis seed development epidermal cells of the seed coat produce large quantities of pectineous mucilage. Following exposure of mature seeds to water, mucilage is released from these cells where upon it forms a thick protective layer around the germinating seed. The seed coat epidermis is therefore an attractive system to investigate the production of cell wall polysaccharides, particularly pectin, which is the main constituent of mucilage. We have previously shown that mutations in the transcriptional regulator LEUNIG_HOMOLOG (LUH) are associated with a mucilage extrusion defect that is caused by reduced expression of the β-galactosidase MUCILAGE MODIFIED2 (MUM2). To better understand the role of LUH in regulating MUM2 we recently performed genome-wide transcriptomic analysis on whole seeds and identified genes that were differentially expressed in luh mutants. This analysis not only revealed elevated expression of transcription factors (TFs) with a known role in epidermal cell differentiation but also several MADS-box TFs. Here we present evidence that these MADS-box TFs are a new class of regulators involved in mucilage production. We demonstrate that these TFs are expressed in the epidermal cells of the seed coat, and that mutations in these genes are associated with mucilage extrusion defects. Finally, we report data identifying several MADS-box TF binding sites within the regulatory sequences of the MUM2 gene and show that these are required for seed coat expression. These findings are integrated into current models describing the regulatory pathways controlling mucilage production.