Postdoctoral Scholar The Pennsylvania State University State College, Pennsylvania
Body of Abstract: The endosperm is the primary nutrient reservoir of maize (Zea mays L.) seed. Specialized cell layers such as the basal endosperm transfer layer and conducting zone actively transport nutrients from the phloem terminals at maternal placentochalaza to the filial endosperm. Such layers are comprised of cells with distinctive wall ingrowths (WI) rich in sugar transporters that provide an increased surface to facilitate intense nutrient transport. We are interested to understand how stem cells at the base of endosperm differentiate into basal endosperm transfer cells (BETCs) and how the unique WI structure is formed. The maize unstable factor for orange1 (Zmufo1) is highly expressed during basal endosperm differentiation. Gain and loss-of-function mutant alleles of Zmufo1 had defects in BETCs that are distinct from each other. Further, we identified abnormal accumulation of sugars, hormones, reactive oxygen species (ROS), oxidative DNA damage, and cell death in the basal endosperm of both mutants. Transcriptome analysis of Zmufo1 mutants showed altered expression of crucial primary metabolism genes, hub transcription factors, and chromatin remodelers. Zmufo1 encodes a nuclear protein (ZmUFO1) with disordered regions that have very low similarity to known proteins. ZmUFO1 interacts with diverse transcriptional regulators and chromatin remodelers. Zmufo1 ectopic overexpression has been previously implicated in DNA methylation of an R2-R3 MYB transcription factor pericarp color1 (Zmp1) that regulated flavonoid pigmentation in the pericarp. Our results indicate a novel role of Zmufo1 in transcriptional regulation during basal endosperm development in maize. Spatiotemporal expression of ZmUFO1 and its interacting transcription factors may be playing a role in the polarized accumulation of sugar, hormone, reactive oxygen species, and sterols that have been implicated in BETC differentiation.