Unique and overlapping functions for the transcriptional regulators KANADI1 and ULTRAPETALA1 in Arabidopsis gynoecium and stamen gene regulation.

Abstract

Plants generate their reproductive organs, the stamens and the carpels, de novo within the flowers that form when the plant reaches maturity. The carpels comprise the female reproductive organ, the gynoecium, a complex organ that develops along several axes of polarity and is crucial for plant reproduction, fruit formation, and seed dispersal. The epigenetic trithorax group (trxG) protein ULTRAPETALA1 (ULT1) and the GARP domain transcription factor KANADI1 (KAN1) act cooperatively to regulate Arabidopsis thaliana gynoecium patterning along the apical-basal polarity axis; however, the molecular pathways through which this patterning activity is achieved remain to be explored. In this study, we used transcriptomics to identify genome-wide ULT1 and KAN1 target genes during reproductive development. We discovered 278 genes in developing flowers that are regulated by ULT1, KAN1, or both factors together. Genes involved in developmental and reproductive processes are overrepresented among ULT1 and/or KAN1 target genes, along with genes involved in biotic or abiotic stress responses. Consistent with their function in regulating gynoecium patterning, a number of the downstream target genes are expressed in the developing gynoecium, including a unique subset restricted to the stigmatic tissue. Further, we also uncovered a number of KAN1- and ULT1-induced genes that are transcribed predominantly or exclusively in developing stamens. These findings reveal a potential cooperative role for ULT1 and KAN1 in male as well as female reproductive development that can be investigated with future genetic and molecular experiments.