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

Abstract

Background: Walnut kernels contain a large amount of unsaturated fatty acids, such as linoleic acid and linolenic acid, which are essential fatty acids for humans and have important effects on growth and health. The main function of fatty acid desaturase (FAD), which is widely distributed in organisms, is to remove hydrogen from carbon chains in the biosynthesis of unsaturated fatty acids to generate C=C bonds.Results: By performing a series of bioinformatics analysis, 24 members of the JrFAD gene family were identified from the genome database of walnut, and then compared with the homologous genes from Arabidopsis. Phylogenetic analysis showed that JrFADs were classified into four subfamilies: the SAD desaturase subfamily, Δ7/Δ9 desaturase subfamily, Δ12/ω-3 desaturase subfamily and "front-end" desaturase subfamily. Meanwhile, the expression of fatty acid synthesis genes in walnut kernels at different developmental stages was analysed by transcriptome sequencing, with expression of JrFAD3-1, which encodes an enzyme involved in linolenic acid synthesis, being particularly prominent. The relative expression level of JrFAD3-1 changed dramatically with the kernel development stages and exhibited a Bell-Shaped Curve. A significant positive correlation was observed between the expression of JrFAD3-1 during 70-100 DAF (Days after flowering) and the content of alpha-linolenic acid during 100-130 DAF, with a correlation coefficient of 0.991. Additionally, JrFAD3-1 was proved closely related to homologous genes in Betula pendula and Corylus heterophylla, indicating that the conserved structure of FADs is consistent with classical plant taxonomy.Conclusion: Twenty-four members JrFADs in walnut were identified and classified into four subfamilies. JrFAD3-1 may play significant roles in the biosynthesis of polyunsaturated fatty acids in walnut.

Genome-Wide Identification and Transcriptional Expression Profiles of Transcription Factor WRKY in Common Walnut (Juglans regia L.)

“…The WRKY gene family in walnut can be divided into four groups, similar to the classification of WRKY genes in Musa acuminate and Musa balbisiana , Castor bean, pineapple, soybean, C. sinensis , C. clementina and C. unshiu , Eucalyptus grandis , Quinoa, Dimocarpus longan , Raphanus sativus , potato, moso bamboo, G. raimondii and G. arboretum , Cassava, willow, Oryza officinalis , peach and Dendrobium officinale . The division of the family in such a manner suggests that the results of our classification were reasonable and reliable [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. In view of the conserved motifs, motifs 5, 9, 1, 2, 8, 10 and 7 were the typical motifs of group I; motifs 1 and 2 were the typical motifs of group II; and motifs 4, 1 and 2 were the typical motifs of group III.…”

“…There is no previous study regarding the WRKY gene in common walnut ( J. regia ) [ 33 , 34 ]. In a recent publication of high-quality common walnut genome data, some gene families and transcript factors were reported in common walnut, such phenylalanine ammonialyase ( PAL) , F-box , fatty acid desaturase ( FAD) , heat stress transcription factors ( HSFs ), nascent polypeptide-associated complex protein ( NAC) and repressor of GAI; gibberellic acid-insensitive RGA and scarecrow SCR ( GRAS ) were also reported [ 35 , 36 , 37 , 38 , 39 , 40 ]. However, comprehensive information regarding the functional characterization of the WRKY gene family in common walnut is still unclear.…”

Insights Into Walnut Lipid Metabolism From Metabolome and Transcriptome Analysis

“…Qingxiang contained more linoleic acid (18:2), while Xin 2 contained more palmitic acid (16:0) and long-chain fatty acids such as behenic acid. FAD2 and FAD3 control, respectively, the conversion of oleic acid to linoleic acid and linoleic acid to linolenic acid (Liu et al, 2020). The expression levels of FAD2 and FAD3 in the transcriptome were higher than those of FAD6 and FAD7/8.…”

In Silico Analysis of Fatty Acid Desaturases Structures in Camelina sativa, and Functional Evaluation of Csafad7 and Csafad8 on Seed Oil Formation and Seed Morphology

“…Particularly, ω-3 fatty acid desaturases have been proven to use C18:2 as substrates to produce 18:3 in the plastid, where FAD7 and FAD8 are located, and in the ER where FAD3 are found [5]. In plants, the accumulation of 18:3 under the activity of ω-3 fatty acid desaturases, particularly FAD3 has been demonstrated in several studies, such as in soybean [108,109], in rice [110], in olive [111][112][113], in peanut [114], in flax [115], in walnuts [116], in cowpea [117], in alfalfa [118], in peach aphid [119] and now in C. sativa, according to the current study.…”