During seedling development, lipid droplets (LDs) serve as an essential energy reserve. Lipolysis is one of the major pathways involve in LD degradation in Arabidopsis, in which LDs are engulfed by tubular peroxisome and degraded by the peroxisome-localized lipase SUGAR DEPENDENT 1 (SDP1) (Eastmmond, 2006; Thazar-Poulot, 2015). In addition, the formation of peroxisome is driven by peroxisomal biogenesis factor peroxin (PEX) 11s.
We have recently demonstrated that a plant-unique endosomal sorting complex required for transport (ESCRT) component termed FREE1 plays an essential role in lipolysis in germinating Arabidopsis seedlings, in which FREE1 acts as a scaffold to link SDP1 and PEX11e together during lipolysis in peroxisome (Huang et al., 2022). However, the underlying mechanisms remain elusive.
In this study we aim to elucidate the molecular mechanisms of FREE1-mediated peroxisome tubulation in Arabidopsis with two major objectives: 1) To study the dynamic formation of peroxisome tubulation in plant cells as visualized by SDP1 and/or PEX11e dynamics via live-cell imaging analysis; and 2) To identify putative FREE1- and/or PEX11e- interacting proteins by biochemical assays, followed by functional analysis on selected protein candidates in transgenic plants.
Our preliminary confocal imaging analysis on transgenic plants expressing XFP fusion with SDP1 or PEX11e showed that peroxisomes exhibit highly dynamics of peroxisome tubulation including tubules elongation, navigation, and connection. In addition, the dynamics of peroxisome tubulation are cell-type specific and developmentally regulated. Here we will present our research progress on this project. Supported by grants from the Research Grants Council (RGC) of Hong Kong and CUHK.