Abstract
Oil palm is the most productive oil crop in the world and composes 36% of the world production. However, the molecular mechanisms of hybrids vigor (or heterosis) between Dura, Pisifera and their hybrid progeny Tenera has not yet been well understood. Here we compared the temporal and spatial compositions of lipids and transcriptomes for two oil yielding organs mesocarp and endosperm from Dura, Pisifera and Tenera. Multiple lipid biosynthesis pathways are highly enriched in all non-additive expression pattern in endosperm, while cytokinine biosynthesis and cell cycle pathways are highly enriched both in endosperm and mesocarp. Compared with parental palms, the high oil content in Tenera was associated with much higher transcript levels of EgWRI1, homolog of Arabidopsis thaliana WRINKLED1. Among 338 identified genes in lipid synthesis, 207 (61%) has been identified to contain the WRI1 specific binding AW motif. We further functionally identified EgWRI1-1, one of three EgWRI1 orthologs, by genetic complementation of the Arabidopsis wri1 mutant. Ectopic expression of EgWRI1-1 in plant produced dramatically increased seed mass and oil content, with oil profile changed. Our findings provide an explanation for EgWRI1 as an important gene contributing hybrid vigor in lipid biosynthesis in oil palm.
Highlights
Oil palm is the most productive oil crop in the world and composes 36% of the world production
As an initial step to know whether there is hybrid vigor of lipid biosynthesis in oil palm, we firstly performed the analysis for the fertile fruit yield per tree per year
Microscopy of 4.5 months after fertilization (MAF) oil palm mesocarp showed, most notably, cells with numerous and more obvious oil droplets were observed in Tenera than in Dura (Supplementary Figure S1A and B)
Summary
Oil palm is the most productive oil crop in the world and composes 36% of the world production. Our findings provide an explanation for EgWRI1 as an important gene contributing hybrid vigor in lipid biosynthesis in oil palm. Heterosis in plants of diverse species is associated with many superior agronomic characteristics, including larger plant stature, increased biomass, growth rate, grain yield, and tolerance to abiotic stresses These heterosis is frequently found in cereal crops such as maize (Zea mays) and rice (Oryza sativa), mainly as hybrids, and many other crops including bread wheat (Triticum aestivum), upland cotton (Gossypium hirsutum), and few in oil crop e.g. canola or rape seed (Brassica napus), are grown as allopolyploids. Identifying the specific molecular mechanisms that are responsible for the phenotypic differences between the hybrid and inbred parents remains a challenge, successes in other plants have been achieved, such as the demonstration of heterosis in yield by the effects of a single gene Single Flowering Truss in tomato[9]. Palm oil contains high levels of carotenoids and vitamin E, which are believed to counter the ravages of chronic diseases such as heart disease and cancer and to delay aging[15]
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