Ravigadevi Sambanthamurthi

Chemistry and biochemistry of palm oil

4. Biochemistry of palm oil ..................................................................................................................................... 510 4.1. Fruit development and oil deposition ...................................................................................................... 510 4.2. Changes in lipid class and fatty acid composition during development of the oil palm mesocarp .................................................................................................................................... 511 4.3. Key enzymes in regulation of fatty acid composition in the oil palm mesocarp ...................................... 514 4.4. Beta-Ketoacyl ACP Synthase II (KAS II)................................................................................................ 515 4.5. Acyl ACP thioesterases ............................................................................................................................ 515 4.6. Stearoyl ACP desaturase .......................................................................................................................... 517 4.7. Lipase activity in the oil palm mesocarp .................................................................................................. 517

Oil palm genome sequence reveals divergence of interfertile species in Old and New worlds

Oil palm is the most productive oil-bearing crop. Although it is planted on only 5% of the total world vegetable oil acreage, palm oil accounts for 33% of vegetable oil and 45% of edible oil worldwide, but increased cultivation competes with dwindling rainforest reserves. We report the 1.8-gigabase (Gb) genome sequence of the African oil palm Elaeis guineensis, the predominant source of worldwide oil production. A total of 1.535 Gb of assembled sequence and transcriptome data from 30 tissue types were used to predict at least 34,802 genes, including oil biosynthesis genes and homologues of WRINKLED1 (WRI1), and other transcriptional regulators, which are highly expressed in the kernel. We also report the draft sequence of the South American oil palm Elaeis oleifera, which has the same number of chromosomes (2n = 32) and produces fertile interspecific hybrids with E. guineensis but seems to have diverged in the New World. Segmental duplications of chromosome arms define the palaeotetraploid origin of palm trees. The oil palm sequence enables the discovery of genes for important traits as well as somaclonal epigenetic alterations that restrict the use of clones in commercial plantings, and should therefore help to achieve sustainability for biofuels and edible oils, reducing the rainforest footprint of this tropical plantation crop.

Loss of Karma transposon methylation underlies the mantled somaclonal variant of oil palm

Somaclonal variation arises in plants and animals when differentiated somatic cells are induced into a pluripotent state, but the resulting clones differ from each other and from their parents. In agriculture, somaclonal variation has hindered the micropropagation of elite hybrids and genetically modified crops, but the mechanism responsible remains unknown. The oil palm fruit ‘mantled’ abnormality is a somaclonal variant arising from tissue culture that drastically reduces yield, and has largely halted efforts to clone elite hybrids for oil production. Widely regarded as an epigenetic phenomenon, ‘mantling’ has defied explanation, but here we identify the MANTLED locus using epigenome-wide association studies of the African oil palm Elaeis guineensis. DNA hypomethylation of a LINE retrotransposon related to rice Karma, in the intron of the homeotic gene DEFICIENS, is common to all mantled clones and is associated with alternative splicing and premature termination. Dense methylation near the Karma splice site (termed the Good Karma epiallele) predicts normal fruit set, whereas hypomethylation (the Bad Karma epiallele) predicts homeotic transformation, parthenocarpy and marked loss of yield. Loss of Karma methylation and of small RNA in tissue culture contributes to the origin of mantled, while restoration in spontaneous revertants accounts for non-Mendelian inheritance. The ability to predict and cull mantling at the plantlet stage will facilitate the introduction of higher performing clones and optimize environmentally sensitive land resources.

The oil palm SHELL gene controls oil yield and encodes a homologue of SEEDSTICK

A key event in the domestication and breeding of the oil palm Elaeis guineensis was loss of the thick coconut-like shell surrounding the kernel. Modern E. guineensis has three fruit forms, dura (thick-shelled), pisifera (shell-less) and tenera (thin-shelled), a hybrid between dura and pisifera. The pisifera palm is usually female-sterile. The tenera palm yields far more oil than dura, and is the basis for commercial palm oil production in all of southeast Asia. Here we describe the mapping and identification of the SHELL gene responsible for the different fruit forms. Using homozygosity mapping by sequencing, we found two independent mutations in the DNA-binding domain of a homologue of the MADS-box gene SEEDSTICK (STK, also known as AGAMOUS-LIKE 11), which controls ovule identity and seed development in Arabidopsis. The SHELL gene is responsible for the tenera phenotype in both cultivated and wild palms from sub-Saharan Africa, and our findings provide a genetic explanation for the single gene hybrid vigour (or heterosis) attributed to SHELL, via heterodimerization. This gene mutation explains the single most important economic trait in oil palm, and has implications for the competing interests of global edible oil production, biofuels and rainforest conservation.

Oil palm vegetation liquor: a new source of phenolic bioactives

Waste from agricultural products represents a disposal liability, which needs to be addressed. Palm oil is the most widely traded edible oil globally, and its production generates 85 million tons of aqueous by-products annually. This aqueous stream is rich in phenolic antioxidants, which were investigated for their composition and potential in vitro biological activity. We have identified three isomers of caffeoylshikimic acid as major components of oil palm phenolics (OPP). The 2,2-diphenyl-1-picrylhydrazyl assay confirmed potent free radical scavenging activity. To test for possible cardioprotective effects of OPP, we carried out in vitro LDL oxidation studies as well as ex vivo aortic ring and mesenteric vascular bed relaxation measurements. We found that OPP inhibited the Cu-mediated oxidation of human LDL. OPP also promoted vascular relaxation in both isolated aortic rings and perfused mesenteric vascular beds pre-contracted with noradrenaline. To rule out developmental toxicity, we performed teratological studies on rats up to the third generation and did not find any congenital anomalies. Thus, these initial studies suggest that OPP is safe and may have a protective role against free radical damage, LDL oxidation and its attendant negative effects, as well as vascular constriction in mitigating atherosclerosis. Oil palm vegetation liquor thus represents a new source of phenolic bioactives.

Efficient Transformation of Oil Palm Protoplasts by PEG-Mediated Transfection and DNA Microinjection

Background Genetic engineering remains a major challenge in oil palm (Elaeis guineensis) because particle bombardment and Agrobacterium-mediated transformation are laborious and/or inefficient in this species, often producing chimeric plants and escapes. Protoplasts are beneficial as a starting material for genetic engineering because they are totipotent, and chimeras are avoided by regenerating transgenic plants from single cells. Novel approaches for the transformation of oil palm protoplasts could therefore offer a new and efficient strategy for the development of transgenic oil palm plants. Methodology/Principal Findings We recently achieved the regeneration of healthy and fertile oil palms from protoplasts. Therefore, we focused on the development of a reliable PEG-mediated transformation protocol for oil palm protoplasts by establishing and validating optimal heat shock conditions, concentrations of DNA, PEG and magnesium chloride, and the transfection procedure. We also investigated the transformation of oil palm protoplasts by DNA microinjection and successfully regenerated transgenic microcalli expressing green fluorescent protein as a visible marker to determine the efficiency of transformation. Conclusions/Significance We have established the first successful protocols for the transformation of oil palm protoplasts by PEG-mediated transfection and DNA microinjection. These novel protocols allow the rapid and efficient generation of non-chimeric transgenic callus and represent a significant milestone in the use of protoplasts as a starting material for the development of genetically-engineered oil palm plants.

The oil palm VIRESCENS gene controls fruit colour and encodes a R2R3-MYB

Oil palm, a plantation crop of major economic importance in Southeast Asia, is the predominant source of edible oil worldwide. We report the identification of the VIRESCENS (VIR) gene, which controls fruit exocarp colour and is an indicator of ripeness. VIR is a R2R3-MYB transcription factor with homology to Lilium LhMYB12 and similarity to Arabidopsis PRODUCTION OF ANTHOCYANIN PIGMENT1 (PAP1). We identify five independent mutant alleles of VIR in over 400 accessions from sub-Saharan Africa that account for the dominant-negative virescens phenotype. Each mutation results in premature termination of the carboxy-terminal domain of VIR, resembling McClintock’s C1-I allele in maize. The abundance of alleles likely reflects cultural practices, by which fruits were venerated for magical and medicinal properties. The identification of VIR will allow selection of the trait at the seed or early-nursery stage, 3-6 years before fruits are produced, greatly advancing introgression into elite breeding material.

Positive outcomes of oil palm phenolics on degenerative diseases in animal models

It is well established that plant phenolics elicit various biological activities, with positive effects on health. Palm oil production results in large volumes of aqueous by-products containing phenolics. In the present study, we describe the effects of oil palm phenolics (OPP) on several degenerative conditions using various animal models. OPP reduced blood pressure in a NO-deficient rat model, protected against ischaemia-induced cardiac arrhythmia in rats and reduced plaque formation in rabbits fed an atherogenic diet. In Nile rats, a spontaneous model of the metabolic syndrome and type 2 diabetes, OPP protected against multiple aspects of the syndrome and diabetes progression. In tumour-inoculated mice, OPP protected against cancer progression. Microarray studies on the tumours showed differential transcriptome profiles that suggest anti-tumour molecular mechanisms involved in OPP action. Thus, initial studies suggest that OPP may have potential against several chronic disease outcomes in mammals.

Opportunities for the Oil Palm via Breeding and Biotechnology

Historical records show that palm oil was initially traded for culinary purposes over 5,000 years ago (Zeven 1967). The oil palm (Elaeis guineensis) originated in West Africa, where it played an important role at the village scale for many centuries (Hardon, Rao and Rajanaidu 1985). Nevertheless, the exact centre of origin within Africa is not known (Corley 1976). In Southeast Asia, where it is one of the most important commercial crops (particularly in Malaysia and Indonesia), it has a rather short history. Four oil palm seedlings were brought from Africa via Mauritius and Amsterdam and planted in Bogor Botanical Gardens in Java (Indonesia) in 1848 (Fig. 11.1). The seedlings were subsequently distributed to Deli, Sumatra (Indonesia) in the 1870s (Whitmore 1973). In Malaysia, up to the late nineteenth century, oil palm was grown as ornamentals. In 1911 and 1912, palms of Deli origin were planted along the avenue in Rantau Panjang in the state of Selangor. Seedlings from the Rantau Panjang palms were planted in TenammaranEstate in 1917 and in Elmina Estate in 1920 in the state of Selangor, which marked the beginning of commercial oil palm cultivation in the country (Kushairi 1992). Ironically Malaysia’s foray into commercial planting of oil palm owes its beginning to unsuccessful coffee (Coffea sp) cultivation at the Tenammaran Estate due to disease and drop in the price of the commodity in the global market (Jagoe 1952). The switch from coffee to oil palm led to the beginning of the commercial cultivation of the latter in Malaysia. Growth of the Malaysian oil palm industry was initially slow, gaining momentum only in the early 1960s when the Government introduced the diversification policy to ease dependence on rubber (Hevea brasiliensis), the major crop then.

Lipid metabolism in oil palm (Elaeis guineensis and Elaeis oleifera) protoplasts

Abstract Protoplasts were enzymatically prepared from the mesocarp of two species of oil palm (Elaeis guineensis Jacq. and E. oleifera HBK and Cortes) 16–20 weeks after anthesis and from rapidly multiplying embryogenic cultures of E. guineensis. The protoplasts were purified by density gradient centrifugation in 20% (w/v) sucrose. Radioactive incorporation studies showed that the protoplasts metabolized [1-14C]acetate to lipids, water-soluble compounds and 14CO2. The [14C]fatty acids obtained consisted mainly of C16: 0, C18: 0 and C18: 1. C16: 1, a very minor fatty acid in palm oil, was also labelled and accounted for 8–39% of total fatty acids synthesized by the mesocarp and embryogenic culture protoplasts. The ratio of labelled C18: 0 to C18: 1 was found to vary with the age of the fruit from which the protoplasts were prepared. Thin layer chromatography (TLC) of the labelled lipids showed the presence of all neutral acylglycerol classes. However the distribution of radiolabel in the various classes differed from those previously reported for oil palm mesocarp [K.C. Oo et al. Lipids, 20 (1985) 205] and embryoid tissue slices [E. Turnham and D.H. Northcote, Phytochem., 23 (1984) 35]. Ozonolysis showed that all the labelled C18: 1 acid was vaccenic acid.