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.

DNA methylation is a process through which methyl groups are added to the DNA molecule, thereby modifying the activity of a DNA segment without changing the sequence. Increasing evidence has shown that DNA methylation is involved in various aspects of plant growth and development via a number of key processes including genomic imprinting and repression of transposable elements. DNA methylase and demethylase are two crucial enzymes that play significant roles in dynamically maintaining genome DNA methylation status in plants. In this work, 22 DNA methylase genes and six DNA demethylase genes were identified in rapeseed (Brassica napus L.) genome. These DNA methylase and DNA demethylase genes can be classified into four (BnaCMTs, BnaMET1s, BnaDRMs and BnaDNMT2s) and three (BnaDMEs, BnaDML3s and BnaROS1s) subfamilies, respectively. Further analysis of gene structure and conserved domains showed that each sub-class is highly conserved between rapeseed and Arabidopsis. Expression analysis conducted by RNA-seq as well as qRT-PCR suggested that these DNA methylation/demethylation-related genes may be involved in the heat/salt stress responses in rapeseed. Taken together, our findings may provide valuable information for future functional characterization of these two types of epigenetic regulatory enzymes in polyploid species such as rapeseed, as well as for analyzing their evolutionary relationships within the plant kingdom.

14-3-3s are general regulatory factors (GF14s or GRFs) involved in a variety of physiological regulations in plants, including the control of flowering time. However, there are poorly relevant reports in rapeseed so far. In this study, we identified a homologous 14-3-3 gene BnGF14-2c (AtGRF2_Like in Brassica napus) in rapeseed based on bioinformatic analysis by using the sequences of the flowering-related 14-3-3s in other plant species. Then, we found that overexpression of BnGF14-2c in the semi-winter rapeseed “93275” promoted flowering without vernalization. Moreover, both yeast two-hybrid and bimolecular fluorescence complementation analysis indicated that BnGF14-2c may interact with two vernalization-related flowering regulators BnFT.A02 and BnFLC.A10., respectively. qPCR analysis showed that the expression of BnFT (AtFT_Like) was increased and the expression of two selected vernalization-related genes were reduced in the overexpression transgenic plants. Further investigation on subcellular localization demonstrated that BnGF14-2c localized in the nucleus and cytoplasm. The results of RNA-seq analysis and GUS staining indicated that BnGF14-2c is ubiquitously expressed except for mature seed coat. In general, the interaction of 14-3-3 and FLC was firstly documented in this study, indicating BnGF14-2c may act as a positive regulator of flowering in rapeseed, which is worthy for more in-depth exploration.