Abstract

Abscisic acid plays an important role in fruit development. However, the effect of ABA on fatty acid biosynthesis in oil palm is still unknown. In this study, ABA treatments (CK, A1–A4) were applied to oil palm fruit at 16 WAP (weeks after pollination), and fatty acids in the mesocarp at 24 WAP were analyzed by GC-MS. Results showed that linoleic acid content under treatment A2 (20 μM ABA) was significantly higher (slightly increased by 8.33%) than the control. Therefore, mesocarp samples of A2, and the control at 16, 20, and 24 WAP was sampled for RNA-Seq. KEGG pathway enrichment analysis showed that 43 genes were differentially expressed in the fatty acid biosynthesis pathway, of which expression of EgFAD2 (unigene 105050201) under 20 μM ABA treatment was 1.84-fold higher than in the control at 20 WAP. Further sequence analysis found that unigene 105050201 had more ABA-responsive elements (ABRE), complete conserved domains, and a C-terminal signaling motif among two FAD2 copies. Furthermore, WGCNA and correlation analysis showed co-expression of EgFAD2 (unigene 105050201) with transcription factors (TFs) (WRI1, AP2-EREBP, bZIP, bHLH, C2C2-Dof, MYB, NAC, and WRKY), ABA signaling genes (PYR, PP2C, SnRK, and ABI5), and other genes involved in fatty acid biosynthesis (FATA, FATB, LACS, SAD, Oleosins, and so on). These results indicated that ABA treatment promoted the expression of FAD2 and other genes involved in fatty acid biosynthesis, which possibly resulted in the accumulation of linoleic acid. This study will be helpful for understanding the possible mechanisms through which ABA affects fatty acid biosynthesis and their accumulation in the mesocarp of oil palm.

Highlights

  • Oil palm (Elaeis guineensis) is a valuable tropical oil crop, providing approximately 36% of edible oils globally (Zhou et al, 2020)

  • Fatty acids are synthesized from pyruvate, while pyruvate dehydrogenase complex (PDH), acetyl-CoA carboxylase (ACCase), malonyl-CoA (MAT), acyl carrier protein (ACP), ketoacyl-ACP synthase (KASI, KASII, and KASIII), ketoacylACP reductase (KAR), hydroxyacyl-ACP dehydrase (HAD), enoyl-ACP reductase (EAR), stearate desaturase (SAD), and acyl-ACP thioesterase (FATA, FATB) participate in the process

  • The content of myristic acid, stearic acid, 10-transnonadecenoate, linoleic acid, arachidonic acid, behenic acid, and lignoceric acid increased significantly in A2 compared to CK, while content of main fatty acids components, such as palmitic acid and oleic acid, had no significant changes (Figure 1 and Supplementary Table 1)

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Summary

Introduction

Oil palm (Elaeis guineensis) is a valuable tropical oil crop, providing approximately 36% of edible oils globally (Zhou et al, 2020). The fruit oil content of oil palm is high (about 50%), while unsaturated fatty acid content (about 50%) is lower than for other oil crops, such as rapeseed and ABA Improves Linoleic Acid Accumulation soybean. Previous reports have shown that fatty acid biosynthesis is mainly involved in carbon chain extension and desaturation. Carbon chain extension takes place within plastids. In this process, fatty acids are synthesized from pyruvate, while pyruvate dehydrogenase complex (PDH), acetyl-CoA carboxylase (ACCase), malonyl-CoA (MAT), acyl carrier protein (ACP), ketoacyl-ACP synthase (KASI, KASII, and KASIII), ketoacylACP reductase (KAR), hydroxyacyl-ACP dehydrase (HAD), enoyl-ACP reductase (EAR), stearate desaturase (SAD), and acyl-ACP thioesterase (FATA, FATB) participate in the process. TAG accumulates in the cytoplasm with the oil formed by caleosin and oleosins proteins

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