Euglena gracilis, a unicellular phytoflagellate, can accumulate a large amount of medium-chain wax esters under anaerobic growth conditions. Here we report the identification and characterization of two genes involved in the biosynthesis of wax esters in E. gracilis. The first gene encodes a fatty acyl-CoA reductase (EgFAR) involved in the conversion of fatty acyl-CoAs to fatty alcohols and the second gene codes for a wax synthase (EgWS) catalyzing esterification of fatty acyl-CoAs and fatty alcohols, yielding wax esters. When expressed in yeast (Saccharomyces cerevisiae), EgFAR converted myristic acid (14:0) and palmitic acid (16:0) to their corresponding alcohols (14:0Alc and 16:0Alc) with myristic acid as the preferred substrate. EgWS utilized a broad range of fatty acyl-CoAs and fatty alcohols as substrates with the preference towards myristic acid and palmitoleyl alcohol. The wax biosynthetic pathway was reconstituted by co-expressing EgFAR and EgWS in yeast. When myristic acid was fed to the yeast, myristyl myristate (14:0-14:0), myristyl palmitoleate (14:0-16:1), myristyl palmitate (14:0-16:0) and palmityl myristate (16:0-14:0) were produced. These results indicate EgFAR and EgWS are likely the two enzymes involved in the biosynthesis of medium-chain wax esters in E. gracilis.
Among starch producing crops, cassava has a higher carbohydrate production than others under suboptimal conditions, more than 163×106 t of cassava starch are produced world‐wide each year and are used for direct human consumption, animal feeds and as raw material for a wide range of industrial products. A basic knowledge of starch characteristics and storage process is required to improve cassava starch quality and quantity. This report describes a comparative study of morphology, starch granule size distribution and amylose content in cassava storage roots grown under different conditions. Microscopic evaluation reveals that storage roots contain larger starch granules than fibrous roots. The study on three Asian cassava cultivars demonstrates the increment of starch granule size from outermost to innermost layers of storage root, while no significant change is observed in amylose content. The effects of developmental stage and growing season on cassava starch reveals that granule size is significantly influenced by both factors, while the amylose contents only fluctuate in a narrow range. The size of the starch granules increases particularly in the first six months after cultivation. Planting cassava in the beginning of the wet season in Asia yields larger granule sizes than planting in the dry season. The significance of this study lies in better understanding optimal growing conditions for improved starch characteristics and production, leading to a better quality agricultural production of this important food and materials crop.
The marine copepod Calanus finmarchicus constitutes the substantial amount of biomass in the Arctic and Northern seas. It is unique in that this small crustacean accumulates a high level of wax esters as carbon storage which is mainly comprised of 20:1n-9 and 22:1n-11 alcohols (Alc) linked with various kinds of fatty acids, including n-3 polyunsaturated fatty acids. The absence of 20:1n-9 Alc and 22:1n-11 Alc in diatoms and dinoflagellates, the primary food sources of copepods, suggests the existence of de novo biosynthesis of fatty alcohols in C.
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