Omega-3 fatty acid desaturase gene family from two ω-3 sources, Salvia hispanica and Perilla frutescens: Cloning, characterization and expression

Abstract

Omega-3 fatty acid desaturase (ω-3 FAD, D15D) is a key enzyme for α-linolenic acid (ALA) biosynthesis. Both chia (Salvia hispanica) and perilla (Perilla frutescens) contain high levels of ALA in seeds. In this study, the ω-3 FAD gene family was systematically and comparatively cloned from chia and perilla. Perilla FAD3, FAD7, FAD8 and chia FAD7 are encoded by single-copy (but heterozygous) genes, while chia FAD3 is encoded by 2 distinct genes. Only 1 chia FAD8 sequence was isolated. In these genes, there are 1 to 6 transcription start sites, 1 to 8 poly(A) tailing sites, and 7 introns. The 5’UTRs of PfFAD8a/b contain 1 to 2 purine-stretches and 2 pyrimidine-stretches. An alternative splice variant of ShFAD7a/b comprises a 5’UTR intron. Their encoded proteins harbor an FA_desaturase conserved domain together with 4 trans-membrane helices and 3 histidine boxes. Phylogenetic analysis validated their identity of dicot microsomal or plastidial ω-3 FAD proteins, and revealed some important evolutionary features of plant ω-3 FAD genes such as convergent evolution across different phylums, single-copy status in algae, and duplication events in certain taxa. The qRT-PCR assay showed that the ω-3 FAD genes of two species were expressed at different levels in various organs, and they also responded to multiple stress treatments. The functionality of the ShFAD3 and PfFAD3 enzymes was confirmed by yeast expression. The systemic molecular and functional features of the ω-3 FAD gene family from chia and perilla revealed in this study will facilitate their use in future studies on genetic improvement of ALA traits in oilseed crops.

Chia Seed (Salvia hispanica L.) as a Source of Proteins and Bioactive Peptides with Health Benefits: A Review

“…The fatty acid desaturases 3, 7, and 8 (FAD3, FAD7, FAD8) are key enzymes responsible for producing α‐linolenic acid (ALA), also called omega‐3 in plants. The FAD3 catalyzes the introduction of a third double bond at the delta‐15/ omega‐3 carbon position of linoleic acid in the endoplasmic reticulum, and the FAD7 and FAD8 in plastids (Xue et al., ). Fatty acid desaturases 2 (FAD2) and 3 (FAD3) are the main enzymes responsible for the delta‐12 and delta‐15 desaturation in plants (Radovanovic, Thambugala, Duguid, Loewen, & Cloutier, ).…”

Identification and analysis of the FAD gene family in walnuts (Juglans regia L.) based on transcriptome data

“…Fatty acid desaturase (FAD) is widely present in organisms [6][7][8][9]. The main function of FAD is to remove hydrogen from carbon chains in the biosynthesis of unsaturated fatty acids to produce C=C bonds.…”

Alpha-linolenic acid content and expression of KASII and FAD3 in perilla seed associated with altitude of cultivation areas

“…In fact, the AP2 and B3 families not only have major roles in seed oil biosynthesis but also dominantly respond to drought, high-salt content, and temperature change in oil seeds 33 . As mentioned previously, the possibility that the increase of kasII and fad3 expression corresponding to the increment of ALA production may be associated with the altitude of growing sites and can be explained by the counteraction of perilla to environmental conditions such as drought and low temperature 27 .…”

“…As perilla is a short-day plant, it needs a long-night period to induce flowering and cold stress for polyunsaturated fatty acid production 26,27 . Thus during the growing season of shortday length, the terrain provides a proper low temperature and dry conditions 28 .…”

“…The exposure of plants to low temperatures during seed maturation and lipid accumulation could then shape the profile of polyunsaturated fatty acids in many developing oil seeds 10,29 . The production of ALA possibly resulted from the interaction of many factors including climate, soil types and conditions, agricultural conditions, genetic diversity, and the ability of plants to adapt to different environments 27,29,30 . In addition, future work should also focus on the question of geographical influences such as altitude, temperature, day-light hours, and humidity on perilla ALA production in more cultivation areas.…”