PS Seminar Series: Revealing the Functions of SEPALLATA MADS-Box Genes in Cereal Floral Organ Development

Abstract: Grass genomes harbour a whole MADS-box gene blueprint of the ABCED model, which is the molecular basis of floral organ identity in angiosperm flowers. While the SEPALLATA (SEP) family E class genes are universally expressed across floral whorls and crucial for flower development in Arabidopsis and rice, the functional role of the SEP genes remain elusive in barley and wheat.

In this seminar, I will present our latest findings focusing on two SEP family members MADS8 and MADS1 in regulating pistil and lemma development. We showed that barley and rice loss-of-function mutants in MADS8 both form multiple carpels that lack ovules at high ambient temperatures. HvMADS8 is required to maintain floral meristem determinacy and ovule initiation at high temperatures, and the high temperature responsive activity of HvMADS8 relies on increased binding to promoters of downstream targets. Furthermore, we also revealed that HvMADS1 positively regulates awn length and lemma width by promoting cell proliferation, affecting grain size and weight. And multi-omics data reveals that HvMADS1 target genes are associated with cell cycle, phytohormone signaling, and developmental processes. Additionally, we demonstrate that HvMADS1 interacts with APETALA2 (A-class) to synergistically activate downstream genes in awn/lemma development in barley.

Overall, our findings revealed new, conserved roles for SEP genes in determining floral organ development across various cereal crops, and the contribution of SEP genes in response to high ambient temperature. These findings extend our understanding of plant MADS-box proteins in floral organ regulation. In the end, I will also briefly touch on some of our current endeavours in improving transformation systems in barley and wheat at the ARC training centre for Future Crops Development.

Biography Dr. Chaoqun Shen received her B.Sc. from Huazhong Agriculture University in 2016 and completed her joint Ph.D. in Plant Developmental Biology at Shanghai Jiao Tong University and the University of Adelaide in 2023. Throughout her Ph.D. academic journey, she focused on unraveling the molecular mechanisms underlying floral organ regulation.

Currently serving as an Innovation Fellow at the Australian Research Council (ARC) Industrial Transformation Training Centre for Future Crops Development, Chaoqun is dedicated to advancing and developing new transformation systems in barley and wheat, with a focus on overcoming recalcitrance through the application of growth-regulating factors.