Abstract
Omega 3 fatty acid desaturases are involved in the production of α-linolenic acid (LNA) an essential omega 3 fatty acid, which is present in only traces in sesame seeds. LNA is the precursor for jasmonic acid which is the end product of octadecanoid pathway. This study was undertaken to analyze the key components of octadecanoid pathway and its relationship with fatty acid content in sesame. Fatty acid desaturation and membrane fluidity are modulated differentially in various stresses. Sesame seedlings were subjected to transient stress to analyse the octadecanoid pathway and its impact on fatty acid desaturation. The mRNA levels of omega 3 desaturases and LNA content were higher in cold stressed sesame seedlings than heat, drought and salinity stresses. The LOX activity and MDA content were higher in heat stressed sesame seedlings. Jasmonic acid content was higher in salinity stressed seedlings while abscisic acid registered the highest in drought stressed seedlings. Chloroplast fatty acid desaturase genes expression was found to increase the LNA content in cold stressed seedlings. The level of membrane damage measured by lipid peroxidation in terms of LOX activity and MDA content were found to be minimal in cold stressed seedling. This suggests a possible role of LNA in membrane fluidity and cold acclimation in sesame. A synergistic role of JA and ABA is also suspected in abiotic stress tolerance in sesame.
Highlights
Sesame (Sesamum indicum L.) is a major oil seed crop characterized with a maximum of 59.8% oil content and the oil is known to be resistant to oxidation and rancidity [1]
The amount of mRNA corresponding to omega3 desaturase genes FAD3, FAD7 and FAD8 present in cold, drought, heat, salt stressed
In soybean GmFAD3A, GmFAD3B and GmFAD3C mRNA levels and omega 3 (18:3) content were found to be higher in cool (20°C) than warm (30°C) growing conditions [29].Short term transient responses of cold stress in olive leaves were found to increase the expression of fatty acid desaturases [30]
Summary
Sesame (Sesamum indicum L.) is a major oil seed crop characterized with a maximum of 59.8% oil content and the oil is known to be resistant to oxidation and rancidity [1]. It is one of the first oil seeds recognized by humankind and more than 80% of the total fatty acids in the sesame oil is composed of oleic (C18:1) and linoleic (LA) (C18:2) acids and trace amounts of linolenic acid (LNA) (C18:3) [2]. Several reports indicate the effect of environmental stress over the lipid composition [9].Omega 3 fatty acid desaturases are enzymes responsible for formation of trienoic fatty acids. Trienoic fatty acid is the precursor of octadecanoid pathway which ends in jasmonic acid (JA) synthesis [10]
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