Abstract
Peanut (Arachis hypogaea L.) is one of the major oil crops and is the fifth largest source of plant oils in the world. Numerous genes participate in regulating the biosynthesis and accumulation of the storage lipids in seeds or other reservoir organs, among which several transcription factors, such as LEAFY COTYLEDON1 (AtLEC1), LEC2, and WRINKLED1 (WRI1), involved in embryo development also control the lipid reservoir in seeds. In this study, the AtLEC1 gene was transferred into the peanut genome and expressed in a seed-specific manner driven by the NapinA full-length promoter or its truncated 230-bp promoter. Four homozygous transgenic lines, two lines with the longer promoter and the other two with the truncated one, were selected for further analysis. The AtLEC1 mRNA level and the corresponding protein accumulation in different transgenic overexpression lines were altered, and the transgenic plants grew and developed normally without any detrimental effects on major agronomic traits. In the developing seeds of transgenic peanuts, the mRNA levels of a series of genes were upregulated. These genes are associated with fatty acid (FA) biosynthesis and lipid accumulation. The former set of genes included the homomeric ACCase A (AhACC II), the BC subunit of heteromeric ACCase (AhBC4), ketoacyl-ACP synthetase (AhKAS II), and stearoyl-ACP desaturase (AhSAD), while the latter ones were the diacylglycerol acyltransferases and oleosins (AhDGAT1, AhDGAT2, AhOle1, AhOle2, and AhOle3). The oil content and seed weight increased by 4.42–15.89% and 11.1–22.2%, respectively, and the levels of major FA components including stearic acid, oleic acid, and linoleic acid changed significantly in all different lines.
Highlights
Peanut (Arachis hypogaea L.) is the fifth largest source of plant oil in the world, after soybean, rapeseed, cotton, and sunflower (de Paula et al, 2017)
Specific bands of ∼500 bp including 63-bp Napin A promoter fragment and of ∼450 bp including the AtLEC1 segment were observed upon polymerase chain reaction (PCR) analysis of the transgenic plants, whereas the untransformed control showed no amplification (Figure 2)
The results showed that the expression levels of AtLEC1 in seeds differed among the different transgenic lines, and the accumulation of mRNA in the lines with the FL Napin A (NapA) promoter was higher than for those with the 230-bp promoter (Figure 3), suggesting that the FL promoter had higher transcriptional activity than the truncated one
Summary
Peanut (Arachis hypogaea L.) is the fifth largest source of plant oil in the world, after soybean, rapeseed, cotton, and sunflower (de Paula et al, 2017). As the demand for plant oils has sharply increased, improving the oil content and quality of oilseed crops has become a major goal globally. Many genes encoding key FA biosynthesis- or lipid reservoir-related enzymes or enzyme subunits from different organisms have been transformed into plants and increased the levels of lipids in transgenic seeds to varying degrees (Shorrosh et al, 1995; Zou et al, 1997; Jako et al, 2001). In some cases the oil content was reduced, for example, by overexpressing the gene encoding spinach 3-ketoacyl-ACP synthase III (KAS III) in transgenic rapeseed seeds (Dehesh et al, 2001). Manipulating only one or a few genes in the pathway of FA synthesis and metabolism sometimes resulted in discordant changes of FA composition and lipid contents
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