Abstract
Summary Jatropha curcas (physic nut), a non‐edible oilseed crop, represents one of the most promising alternative energy sources due to its high seed oil content, rapid growth and adaptability to various environments. We report ~339 Mbp draft whole genome sequence of J. curcas var. Chai Nat using both the PacBio and Illumina sequencing platforms. We identified and categorized differentially expressed genes related to biosynthesis of lipid and toxic compound among four stages of seed development. Triacylglycerol (TAG), the major component of seed storage oil, is mainly synthesized by phospholipid:diacylglycerol acyltransferase in Jatropha, and continuous high expression of homologs of oleosin over seed development contributes to accumulation of high level of oil in kernels by preventing the breakdown of TAG. A physical cluster of genes for diterpenoid biosynthetic enzymes, including casbene synthases highly responsible for a toxic compound, phorbol ester, in seed cake, was syntenically highly conserved between Jatropha and castor bean. Transcriptomic analysis of female and male flowers revealed the up‐regulation of a dozen family of TFs in female flower. Additionally, we constructed a robust species tree enabling estimation of divergence times among nine Jatropha species and five commercial crops in Malpighiales order. Our results will help researchers and breeders increase energy efficiency of this important oil seed crop by improving yield and oil content, and eliminating toxic compound in seed cake for animal feed.
Highlights
Sustainable biofuel has been receiving increasing attention as an alternative energy source to fossil fuels due to increasing greenhouse gas emissions and energy consumption
To construct a genetic map, we genotyped 108 F2 lines derived from a cross between J. curcas Chai Nat (CN) and J. curcas M10 by genotyping-by-sequencing (GBS) (Elshire et al, 2011), with an average mapping depth of 159 (Data S2) (Li et al, 2009)
Core Eukaryotic Genes Mapping Approach (CEGMA) analysis showed that 85.9% of core eukaryotic gene sequences were complete (97.2% were partial), and Benchmarking Universal Single-Copy Orthologs (BUSCO) showed that 82.5% of embryophyta gene sequences were complete (87.8% were partial), in our assembly (Table S3; Parra et al, 2007; Sim~ao et al, 2015)
Summary
Sustainable biofuel has been receiving increasing attention as an alternative energy source to fossil fuels due to increasing greenhouse gas emissions and energy consumption. Jatropha curcas (physic nut), a non-edible oilseed crop, is one of the most promising biofuel feedstocks because it has high seed oil content, drought tolerance, rapid growth and adaptability to a wide range of climatic and soil conditions (Kumar and Sharma, 2008). Physic nut is a perennial, monoecious tree or shrub belonging to the Euphorbiaceae family, which includes many economically important crops such as rubber tree (Hevea brasiliensis), cassava (Manihot esculenta) and castor bean (Ricinus communis). It has very small chromosomes (1.24–1.71 lm) with 2n = 2x = 22 and a relatively small genome size (C = 416 Mb) (Carvalho et al, 2008).
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