Subcellular localisation of Arabidopsis seipins, a plant protein family homologue to human Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2)

In humans, the autosomal recessive Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2), caused by mutations in the BSCL2 gene encoding a protein known as seipin, is characterised by an almost completely absence of adipose tissue and low but detectable lipid content. The seipin protein family appears to widely spread in animals, plants and some microorganisms. In yeast, seipin is localised at the endoplasmic reticulum-lipid droplet (ER-LD) junction and its absence resulted in irregular LDs, clustered together. LDs are found in nearly all eukaryotic cells and in some prokaryotes and function as an energy-storage reservoir in the form of neutral lipids, predominantly triacylglycerols and steryl esters. LD consist of a neutral lipid core surrounded by a phospholipid monolayer with acyl chains deeply inserted into the core and are originated from the (ER), even though the precise mechanisms underlying their biogenesis remains largely unclear. In Arabidopsis thaliana, similarly to other plant species, homologues to human and yeast seipins have been identified and are encoded by a gene family. However their physiological significance is completely unknown. Here we report about subcellular localisation of the three Arabidopsis thaliana seipins by CLSM in tobacco leaves. These results together with the peculiar expression pattern of the seipin genes allowed us to speculate about possible physiological roles of this class of proteins in plants.