Lipid droplets accumulation and other biochemical changes induced in the fungal pathogen Ustilago maydis under nitrogen-
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ORIGINAL PAPER
Lipid droplets accumulation and other biochemical changes induced in the fungal pathogen Ustilago maydis under nitrogen‑starvation Lucero Romero Aguilar1,2,3 · Juan Pablo Pardo2 · Mónica Montero Lomelí3 · Oscar Ivan Luqueño Bocardo2 · Marco A. Juárez Oropeza2 · Guadalupe Guerra Sánchez1
Received: 17 January 2017 / Revised: 28 April 2017 / Accepted: 16 May 2017 © Springer-Verlag Berlin Heidelberg 2017
Abstract In many organisms, the growth under nitrogendeprivation or a poor nitrogen source impacts on the carbon flow distribution and causes accumulation of neutral lipids, which are stored as lipid droplets (LDs). Efforts are in progress to find the mechanism of LDs synthesis and degradation, and new organisms capable of accumulating large amounts of lipids for biotechnological applications. In this context, when Ustilago maydis was cultured in the absence of a nitrogen source, there was a large accumulation of lipid bodies containing mainly triacylglycerols. The most abundant fatty acids in lipid bodies at the stationary phase were palmitic, linoleic, and oleic acids, and they were synthesized de novo by the fatty-acid synthase. In regard to the production of NADPH for the synthesis of fatty acids, the
cytosolic NADP+-dependent isocitrate dehydrogenase and the glucose-6-phosphate and 6-phosphogluconate dehydrogenases couple showed the highest specific activities, with a lower activity of the malic enzyme. The ATP-citrate lyase activity was not detected in any of the culture conditions, which points to a different mechanism for the transfer of acetyl-CoA into the cytosol. Protein and RNA contents decreased when U. maydis was grown without a nitrogen source. Due to the significant accumulation of triacylglycerols and the particular composition of fatty acids, U. maydis can be considered an alternative model for biotechnological applications. Keywords Lipid droplets · Lipid metabolism · Nitrogenstarvation · Ustilago maydis
Communicated by Erko Stackebrandt. Guadalupe Guerra Sánchez and Juan Pablo Pardo share the senior co-authorship as corresponding authors. Electronic supplementary material The online version of this article (doi:10.1007/s00203-017-1388-8) contains supplementary material, which is available to authorized users. * Juan Pablo Pardo [email protected] * Guadalupe Guerra Sánchez [email protected] 1
Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad De México, Mexico
2
Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad De México, Mexico
3
Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio De Janeiro, Brazil
Introduction Lipid droplets (LDs) are ubiquitous intracellular fat bodies composed of a core of neutral lipids, mainly triacylglycerols (TAGs) and sterol esters (SEs). Most of the enzymes involved in TAGs, SEs, and LDs syntheses are located in the endoplasmic reticulum (Martin and Parton 2006; Thiam et al. 2013). Although the exact mechanism of biogen
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