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Plant Responses and Mechanisms of Tolerance to Cold Stress
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Aruna V. Varanasi, Nicholas E. Korres, Vijay K. Varanasi
The effect of low temperature stress on lipid metabolism is negatively correlated as the transcript levels of lipid metabolism genes are generally repressed (Hannah et al., 2006). However, some lipid catabolism enzymes such as phospholipase A and D may be activated by low temperature, followed by an increase in the amount of free fatty acids (Wang et al., 2006; Usadel et al., 2008). Phospholipase D functions in the degradation of membrane lipids and its suppression may be necessary to enhance freezing tolerance (Rajashekar, 2000). Galactolipases, belonging to the hydrolase family, are also induced during cold acclimation but at considerably lower levels compared to the phospholipases (Kaniuga, 2008). At low temperatures, acyl-lipid desaturases, an important class of desaturases, introduce double bonds into fatty acids esterified to glycerolipids to enhance the molecular activities in the lipids of both plastid and endoplasmic reticulum membranes (Jin et al., 2001; Maali et al., 2007). This action regulates the level of unsaturation of membrane lipids and remodels the cell membrane structure and function to facilitate adaptation to temperature changes (Somerville and Browse, 1991; Wada et al., 1994; Murata and Wada, 1995).
Potential of Oleaginous Microorganisms in Green Diesel Production
Published in V. Sivasubramanian, Bioprocess Engineering for a Green Environment, 2018
R. Selvaraj, I. Ganesh Moorthy, V. Sivasubramanian, R. Vinoth Kumar, R. Shyam Kumar
Desaturase and elongase are the enzymes that convert palmitic acid into unsaturated or polyunsaturated fatty acids. The introduction of double bond(s) into the fatty acid chain is catalyzed by desaturase, and elongase increases the length of the C2 units.
Lowering the culture medium temperature improves the omega-3 fatty acid production in marine microalga Isochrysis sp. CASA CC 101
Published in Preparative Biochemistry & Biotechnology, 2021
Jeyakumar Balakrishnan, Kathiresan Shanmugam
Fatty acid desaturases (FADs) add a double bond to the growing fatty acid chain in omega-3 fatty acid metabolism. The mRNA expression of three desaturases Δ6Des, Δ5Des, and Δ4Des showed a significant difference in their pattern (Figure 3). Δ6Des is an important rate-limiting enzyme in the omega-3 pathway. There was no significant difference in the expression of Δ6Des between the two treatments. Furthermore, Δ5Des which add a double bond to eicosatetraenoic acid to form eicosapentaenoic acid (EPA) in the omega-3 pathway. The expression of Δ5Des was highly up-regulated in cultures grown in low temperature (18 °C) than the cultures grown in (22 °C) (Figure 3). Finally, Δ4Des adds a double bond to docosapentaenoic acid (DPA) to form DHA in the pathway. The expression of Δ4Des was highly up-regulated in cultures grown in low temperature (18 °C) than the cultures grown in (22 °C) (Figure 3). The expression of two front end desaturases (Δ4Des & Δ5Des) is highly favorable for the cultures grown at low temperature indicates the high demand of EPA and DHA at the cellular level for the maintenance of cell membrane. Temperature shift favors the synthesis of long-chain PUFAs particularly EPA and DHA in microalgae for the adaptation of membrane lipids and internal organelles toward changing environment. Interestingly the mRNA expression of respective desaturases was highly similar to the fatty acid profile of microalgal cells grown at low temperatures. In RSM treatments, microalga grown under low-temperature treatments (such as R3, R4, R6, and R20) showed higher accumulation of EPA and DHA in their fatty acid profile (Supplementary Table 1).