Regulation of the cholesterol biosynthetic pathway and its integration with fatty acid biosynthesis in the oleaginous microalga Nannochloropsis oceanica

Table 1 GC/MS data for sterol profiling from N. oceanica treated with sterol biosynthetic inhibitors

Sterols	Structure	RT (min)	RRTc	Sterol profile (%)
Sterols	Structure	RT (min)	RRTc	Control	CLO	TBF	TEB	TDM	25-AZA
Squalene	1	10.25	0.755	-*	-	12.0	-	-	-
Cholesterol	2	13.58	1.000	74.0	70.4	61.6	62.0	56.2	81.3
Cholest-8-enol	3	13.75	1.012	-	-	-	-	8.2	-
Desmosterol	4	13.91	1.024	-	-	-	-	-	3.0
Pollinastanol	5	14.33	1.056	-	-	-	-	13.1	-
4, 14-Dimethylcholest-8-enol	6	14.53	1.070	-	-	-	1.7	-	-
24-Methylenecholesterol	7	14.59	1.074	1.4	2.5	0.7	2.7	-	4.0
24(25)-Dihydrolanosterol	8	15.18	1.117	-	-	-	1.7	-	-
4-Methylpollinasterol	9	15.47	1.139	-	-	-	-	3.7	-
24-Methylcholesta-5, 25(27)-dienol	10	15.51	1.142	0.9	1.0	0.9	0.8	0.3	1.0
Fucosterol	11	15.68	1.155	10.1	10.1	10.3	7.2	6.8	6.0
Obtusifoliol	12	15.73	1.158	-	-	-	0.2	-	-
Isofucosterol	13	15.91	1.171	13.5	16.1	14.3	8.9	9.3	4.8
Stigmasta-8, 24(28) E-dienol	14	15.93	1.173	-	-	-	-	0.4	-
Cycloartenol	15	16.06	1.182	-	-	-	12.8	-	-
Stigmasta-8, 24(28) Z-dienol	16	16.16	1.190	-	-	-	-	1.9	-
Cycloartanol	17	16.59	1.222	-	-	-	2.1	-	-

Cultures in exponential phase were diluted in fresh media and grown for 12 h under 50 μmol photons m^-2 s^-1 light. Subsequently, cultures were treated with inhibitors at a concentration of IC₅₀ or an equivalent amount of DMSO (not exceeding a final concentration of 0.1%). Cell aliquots were collected for sterol profiling four days later. Three biological replicates of algal cultures were established under each treatment. Abbreviations: RRTc, relative retention time to cholesterol; CLO, clomazone; TBF, terbinafine; TEB, tebuconazole; TDM, tridemorph; 25-AZA, 25-azalanosterol. The asterisk (*) indicates a value below the detection limit under current experimental conditions. The structure numbers in boldface are listed in Additional file 2: Figure S3.