UC Riverside

Lateral organs form from the shoot apical meristem (SAM) and are separated from the SAM by the boundary region, an area of restricted growth. In Arabidopsis, the MYB-domain transcription factor LATERAL ORGAN FUSION1 (LOF1) is expressed in organ boundaries. LOF1 functions in organ separation and meristem formation. The focus of this dissertation is to characterize the molecular function of LOF1. In Chapter 1, proteins that interact with LOF1 were identified. These include transcription factors with documented roles in a variety of plant processes, including development, the shade-avoidance response, plastid DNA repair, and other environmental responses. Because many of the LOF1 interactors identified were localized to either the plastid or mitochondria and were involved in response to abiotic stress, we investigated the subcellular localization of LOF1-GFP in response to abiotic stress conditions in the root in Chapter 2. Simulated drought, exposure to high light conditions, and the presence of reactive oxygen species (ROS) did not change the subcellular localization of LOF1-GFP. In Chapter 3, a dominant mutation in PHABULOSA (PHB), a transcription factor involved in meristem regulation and leaf polarity, was found to be a genetic suppressor of the lof1-1 mutation. Our results suggest PHB and LOF1 do not regulate one another at the transcriptional level. Observations of plant architecture in lof1-1 and phb-13 loss-of-function mutants and transgenic plants expressing PHB under its native promoter revealed complex interactions between LOF1 and PHB to promote accessory bud formation and overall plant architecture.