Differential expression of carotenoids under overload and h2o2 in Rhodotorula Nucilaginosa rcl-11

Abstract

There are enzymatic and not enzymatic systems involved in cells defense under diverse stresses. Superoxide dismutase (SODs) and catalase represent the primary enzymatic defense against ROS. Nonenzymatic antioxidants can be carotenoids, glutathione, ascorbate, tocopherol, flavonoids, and alkaloids. Carotenoids are isoprenoid membrane-protective antioxidant pigments with the capacity of to interact with reactive oxygen species. Organisms subject to routine metal exposure in their natural environments generally have had to develop resistance mechanisms. Rhodotorula mucilaginosa RCL-11, yeast isolated from a copper filter plant at Tucumán Argentina, has the ability of supporting high amounts of copper metal. Also, RCL-11 showed high carotenoids contents, obtained by absorption spectrum (330nm-600nm). We observed that copper overload and inhibition of carotenoids synthesis (by diphenylamine, DPA) have a negative effect in viability of Rhodotorula mucilaginosa RCL in addition, combination of cooper and DPA showed the lowest growth rate. We found that when the cells grow in 0.5mM copper, carotenoids synthesis is strongly stimulated. Accordingly, carotenoids content is triplicate in copper overload. Moreover, superoxide dismutase activity and catalase activity was assayed in the same copper concentration. We observed an increased in both antioxidants enzymes as a response of copper excess.Total carotenoids content, as well as its spectral characteristics differs when cells are exposed to copper or 5mM (oxidant agent). A qualitative study was carried out using HPLC equipped with an online diode-array detector. Detection was performed at 490 nm, and UV?vis absorption spectra were recorded online with the photodiode-array detection system. We obtained quantitative and qualitative differences in carotenoids characteristics depending on the content of copper, hydrogen peroxide, both or neither in the culture medium. For example, in presence of H2O2 were mostly expressed torulene, alfa-carotene and beta-carotene, while copper stimulated production of torularhodin. The results obtained in the present work show that when exposing R. mucilaginosa RCL-11 to prooxidant agents as copper and/or H2O2 it is produced an antioxidant enzymatic response and a carotenoids synthesis stimulation.