Control mechanisms operating for lipid biosynthesis differ in oil-palm (Elaeis guineensis Jacq.) and olive (Olea europaea L.) callus cultures

Abstract

As a prelude to detailed flux control analysis of lipid synthesis in plants, we have examined the latter in tissue cultures from two important oil crops, olive (Olea europaea L.) and oil palm (Elaeis guineensis Jacq.). Temperature was used to manipulate the overall rate of lipid formation in order to characterize and validate the system to be used for analysis. With [1-14C]acetate as a precursor, an increase in temperature from 20 to 30 degrees C produced nearly a doubling of total lipid labelling. This increase in total lipids did not change the radioactivity in the intermediate acyl-(acyl carrier protein) or acyl-CoA pools, indicating that metabolism of these pools did not exert any significant constraint for overall synthesis. In contrast, there were some differences in the proportional labelling of fatty acids and of lipid classes at the two temperatures. The higher temperature caused a decrease in polyunsaturated fatty acid labelling and an increase in the proportion of triacylglycerol labelling in both calli. The intermediate diacylglycerol was increased in olive, but not in oil palm. Overall the data indicate the suitability of olive and oil-palm cultures for the study of lipid synthesis and indicate that de novo fatty acid synthesis may exert more flux control than complex lipid assembly. In olive, diacylglycerol acyltransferase may exert significant flux control when lipid synthesis is rapid.

Metabolic control analysis reveals an important role for diacylglycerol acyltransferase in olive but not in oil palm lipid accumulation

“…Thus, for example, when lipid accumulation in developing oilseed rape embryos was maximal there was noticeable diacylglycerol (DAG) accumulation [17,21] indicating a constraint in flux at the level of its conversion to TAG. Previous experiments in our laboratory had shown that it was possible to enhance TAG formation several-fold by increasing the incubation temperature from 20 to 30°C with both types of callus cultures [12]. Therefore, in order to see if there were indications that DAGAT could exert strong flux control in either olive or oil palm cultures, we carried out incubations at the two temperatures.…”

“…Without measuring individual flux control coefficients for the other enzymes of the pathway it is not possible to say where most of the control lies. However, based on the data with temperature manipulation of [12] or oleate addition to [13] callus cultures, we conclude that glycerol 3-phosphate acyltransferase may be important. This conclusion could also be supported by the data in Table 1, where a doubling of carbon flux to TAG did not produce any significant changes to the proportional labelling of the pathway intermediates.…”

“…More details of the method and its application can be found in Fell [11]. We applied topdown MCA to lipid formation in tissue cultures from two important oil crops, olive and oil palm [12,13]. These experiments revealed that lipid synthesis was shared between fatty acid formation and lipid assembly, but with the former exerting greater control ( 60%).…”

Fatty acid profiles of varietal virgin olive oils (<i>Olea europaea</i> L.) from mature orchards in warm arid valleys of Northwestern Argentina (La Rioja)

“…Potentially, metabolic differences in lipid metabolism between olive and other oil crops are responsible for these divergent results. For example, various studies have shown differences in the metabolic control of oil synthesis in olive and oil palm (Elaeis guineensis) (Ramli et al, 2002;2005). Thus, olive may be an interesting alternative model to oilseed crops (Hernández et al, 2005).…”

Differential Expression Analysis of Oil Palm Fatty Acid Biosynthetic Enzymes With Gel-Free Quantitative Proteomics

“…Genetic engineering has been used to generate transgenic oil palms containing more high-value fatty acids to boost sustainability (Parveez et al, 2015). Biochemical studies of lipid biosynthetic pathway revealed significant flux control in the fatty acid biosynthesis over lipid assembly and the results also suggested that manipulation of a single enzyme step would not affect the product yield appreciably (Ramli et al, 2002b). Therefore, understanding the mechanism of fatty acid production in oil palm fruit is essential before any work to increase the content of targeted unsaturated fatty acids through genome editing technologies or metabolic engineering (Maeder and Gersbach, 2016;Thelen and Ohlrogge, 2002a;Schultz and Ohlrogge, 2001).…”