The subcellular distribution of carotenoids in light‐grown Verticillium agaricinum

Abstract

Hyphae of light‐grown V. agaricinum (Link) Corda contain many lipid bodies. The hypae were disrupted and the membranes immediately pelleted by a 48 000 g spin for 30 min. The major part (90%) of the carotenoids was found in a lipid layer on top of the supernatant. Carotenoids extracted from the lipid layer in diethyl ether had an absorption maximum at 488 nm. On the basis of spectra in different organic solvents the main component was tentatively. Thin layer chromatography of extracted and saponified carotenoids revealed the presence of one major and one minor component.The 48 000 g pellet contained 80% of the NAD+‐dependent malate dehydrogenase (marker for mitrochondria), 25% of the antimycin‐resistant NADH‐cytochrome c reductase (marker for mitochodria and endoplasmic reticulum) and 10% of the proteins and the carotenoids. The latter were different from the carotenoids in the lipid layer in that the absorption maximum was at 471 nm in diethyl ether.Further fractionation of the 48 000 g pellet showed the presence of carotenoids in both mitochondria and endoplasmic reticulum (ER) all with an absorption maximum at 471 nm. On a thin layer plate these carotenoids migrated in one band coinciding with the minor band of the lipid layer. On a continous Percoll gradient two main areas of mitochodrial activity (1.068 and 1.063 g ml−1) were clearly separated from the ER (1.059 g ml−1). The carotenoid content was about 0.6 and 0.7–1.0 μg (mg protein)−1 for mitochondria and ER, respectively, equivalent to 1–2 carotenoid molecules per 1000 lipid molecules. The possible role of these membrane‐bound carotenoid molecules is discussed.