The effect of polyunsaturated fatty acids on the homeostasis of yolk lipoprotein in C. elegans examined by CARS and two-photon excitation fluorescence (TPE-F) microscopy

Abstract

Yolk lipoprotein constitutes the major source of energy and the materials for synthesizing signaling factors for the development of oocytes and embryos in C. elegans . Polyunsaturated fatty acids (PUFAs) packed in yolk lipoprotein have been recently recognized as critical molecules for fertilization and reproduction. 1 However, the relation between PUFAs and the homeostasis of yolk lipoprotein is not clear. Here we use coherent anti-Stokes Raman scattering (CARS) microscopy and two-photon excitation fluorescence (TPE-F) microscopy to examine the transportation of yolk lipoprotein. We demonstrate that CARS microscopy is a more sensitive method than the traditional Nile Red staining method in probing the abnormal accumulation of yolk lipoprotein in the body cavity of C. elegans . It is found that the accumulation of yolk lipoprotein is a time-dependent process. In addition, a negative correlation (r = -0.955) between reproductive aging and abnormal accumulation of yolk lipoprotein is established. We further examine wild-type, fat-1 , and fat-2 worms with or without the expression of GFP-tagged yolk lipoprotein (VIT-2-GFP). Our data reveal that PUFAs have a positive effect on the synthesis and endocytosis of yolk lipoprotein, confirming the model proposed by Edmonds et al . 2