https://www.cell.com/molecular-plant/pdf/S1674-2052(15)00366-4.pdf

Amino Acid Catabolism in Plants

The genome sequence of the African oil palm, the main source of oil production, is used to predict at least 34,802 genes, including oil biosynthesis genes; comparison with the draft sequence of the South American oil palm reveals that the two species may have diverged in the New World and that segmental duplications of chromosome arms define the palaeotetraploid origin of palm trees. Two papers published in this issue of Nature deal with the genetics of two variants of one of the most important crops in use today — the African oil palm Elaeis guineensis and its South American cousin Elaeis oleifera. Palm oil accounts for almost half the edible oil consumed worldwide and is also a biofuel, although not without controversy, as in many areas palm oil monoculture has replaced valuable natural forest. Analyses of the 1.8-gigabase genome sequence of E. guineensis and draft sequence of E. oleifera provide insights into oil biosynthesis genes and their regulators, and a record of genome evolution. A key event in the domestication and breeding of the oil palm was loss of the thick, coconut-like shell. The second of the two papers identifies mutations the SHELL gene that specify the different fruit forms found in the oil palm and shows that SHELL gene mutations that originated in pre-colonial Africa are responsible for the single gene hybrid vigour and high yields attained by the oil palm. 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 regulators1, 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. guineensis2 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 plantings3, and should therefore help to achieve sustainability for biofuels and edible oils, reducing the rainforest footprint of this tropical plantation crop.

/pdf/oil-palm-genome-sequence-reveals-divergence-of-interfertile-2owj8qdf95.pdf

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

Biochemical pathways in seed oil synthesis

Compartmentation of Triacylglycerol Accumulation in Plants

Biogenesis and functions of lipid droplets in plants: Thematic Review Series: Lipid Droplet Synthesis and Metabolism: from Yeast to Man

Oil palm can accumulate up to 90% oil in its mesocarp, the highest level observed in the plant kingdom. In contrast, the closely related date palm accumulates almost exclusively sugars. To gain insight into the mechanisms that lead to such an extreme difference in carbon partitioning, the transcriptome and metabolite content of oil palm and date palm were compared during mesocarp development. Compared with date palm, the high oil content in oil palm was associated with much higher transcript levels for all fatty acid synthesis enzymes, specific plastid transporters, and key enzymes of plastidial carbon metabolism, including phosphofructokinase, pyruvate kinase, and pyruvate dehydrogenase. Transcripts representing an ortholog of the WRI1 transcription factor were 57-fold higher in oil palm relative to date palm and displayed a temporal pattern similar to its target genes. Unexpectedly, despite more than a 100-fold difference in flux to lipids, most enzymes of triacylglycerol assembly were expressed at similar levels in oil palm and date palm. Similarly, transcript levels for all but one cytosolic enzyme of glycolysis were comparable in both species. Together, these data point to synthesis of fatty acids and supply of pyruvate in the plastid, rather than acyl assembly into triacylglycerol, as a major control over the storage of oil in the mesocarp of oil palm. In addition to greatly increasing molecular resources devoted to oil palm and date palm, the combination of temporal and comparative studies illustrates how deep sequencing can provide insights into gene expression patterns of two species that lack genome sequence information.

/pdf/comparative-transcriptome-and-metabolite-analysis-of-oil-4mcc7z5g6y.pdf

Comparative transcriptome and metabolite analysis of oil palm and date palm mesocarp that differ dramatically in carbon partitioning.

The oil palm fruit mesocarp contains high lipase activity that increases free fatty acids and necessitates post-harvest inactivation by heat treatment of fruit bunches. Even before heat treatment the mesocarp lipase activity causes consequential oil losses and requires costly measures to limit free fatty acids quantities. Here we demonstrate that elite low-lipase lines yield oil with substantially less free fatty acids than standard genotypes, allowing more flexibility for post-harvest fruit processing and extended ripening for increased yields. We identify the lipase and its gene cosegregates with the low-/high-lipase trait, providing breeders a marker to rapidly identify potent elite genitors and introgress the trait into major cultivars. Overall, economic gains brought by wide adoption of this material could represent up to one billion dollars per year. Expected benefits concern all planters but are likely to be highest for African smallholders who would be more able to produce oil that meets international quality standards.

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers17-10/010060628.pdf

Improving palm oil quality through identification and mapping of the lipase gene causing oil deterioration

Comparative transcriptome and metabolite analysis of oil palm and date palm mesocarp that differ dramatically in carbon partitioning (Proceedings of the National Academy of Sciences of the United States of America (2011) 108, 30 (12527-12532) DOI: 10.1073/pnas.1106502108)

Fabienne Bourgis

Papers

Comparative transcriptome and metabolite analysis of oil palm and date palm mesocarp that differ dramatically in carbon partitioning.

Improving palm oil quality through identification and mapping of the lipase gene causing oil deterioration

Comparative transcriptome and metabolite analysis of oil palm and date palm mesocarp that differ dramatically in carbon partitioning (Proceedings of the National Academy of Sciences of the United States of America (2011) 108, 30 (12527-12532) DOI: 10.1073/pnas.1106502108)