Jatropha curcas, a biofuel crop: functional genomics for understanding metabolic pathways and genetic improvement

Abstract

Jatropha curcas is currently attracting much attention as an oilseed crop for biofuel, as Jatropha can grow under climate and soil conditions that are unsuitable for food production. However, little is known about Jatropha, and there are a number of challenges to be overcome. In fact, Jatropha has not really been domesticated; most of the Jatropha accessions are toxic, which renders the seedcake unsuitable for use as animal feed. The seeds of Jatropha contain high levels of polyunsaturated fatty acids, which negatively impact the biofuel quality. Fruiting of Jatropha is fairly continuous, thus increasing costs of harvesting. Therefore, before starting any improvement program using conventional or molecular breeding techniques, understanding gene function and the genome scale of Jatropha are prerequisites. This review presents currently available and relevant information on the latest technologies (genomics, transcriptomics, proteomics and metabolomics) to decipher important metabolic pathways within Jatropha, such as oil and toxin synthesis. Further, it discusses future directions for biotechnological approaches in Jatropha breeding and improvement.

Keywords: Biofuel; Breeding; Domestication; Purging nut.

Figure 1

The biosynthesis pathway of the FAs in plants. ACC, acetyl-CoA carboxylase; ACP, acyl carrier protein; CoA, coenzyme-A; CPT, CDP-choline:diacylglycerol cholinephosphotransferase; DAG, diacylglycerol synthase; DGAT, diacylglycerol acyltransferase (DGAT1;DGAT2); DHAP, dihydroxyacetone phosphate; FAD2, oleoyl-phosphatidylcholine Δ-12 desaturase; FAD3, linoleoyl-phosphatidylcholine ω-3 desaturase; FAD6, Δ-12 desaturase; FAD7/8, ω-3 desaturase; FATA, stearoyl-ACP thioesterase A ; FATB, Palmitoyl-ACP thioesterase; FBP, fructose bisphosphate; GA3P, glyceraldehyde-3-phosphate; G3P, glycerol-3-phosphate; GPAT, glycerol-3-phosphate O acyltransferase; GPDH, glycerol-3-phosphate dehydrogenase; LPA, lysophosphatidic acid; LPAT, lyso PA acyltransferase); LPCAT, lyso PC acyltransferase; LPAP, lyso PA phosphatase; MAT, ACP-S-malonyl transferase; MGDG, galactolipid monogalactosyldiacylglycerol; KAS, beta-ketoacyl-ACP synthase (KAS I; KASII; KAS III); PA, phosphatidic acid; PACPD, palmitoleoyl-ACP Δ9-desaturase; PC, phosphatidylcholine; PDCT, phosphatidylcholine:diacylglycerol cholinephosphotransferase; PDH, pyruvate dehydrogenase; PEP, phosphoenolpyruvate; PK, pyruvate kinase; Pyr; pyruvate; SACPD, stearoyl-ACP Δ9-desaturase; TAG, triacylglycerol; TPI, triose-phosphate isomerase.

Figure 2

The biosynthesis pathway of the major terpenoids in plants. AACT, acetoacetyl-CoA thiolase; AcAc-CoA, acetoacetyl-CoA; CDP-ME, 4-(cytidine 50-diphospho)-2-C-methyl-d-erythritol; CDP-ME2P, 4-(cytidine 50-diphospho)-2-C-methyl-d-erythritol phosphate; CMK, CDP-ME kinase; DMAPP, dimethylallyl diphosphate; DOXP, 1-deoxy-d-xylulose 5-phosphate; DXR, DOXP reductoisomerase; DXS, DOXP synthase; FDS, farnesyl diphosphate synthase; FPP, farnesyl diphosphate; GA3P, glyceraldehyde-3-phosphate; GDS, geranyl diphosphate synthase; GGDS, geranylgeranyl diphosphate synthase; GGPP, geranylgeranyl diphosphate; GPP, geranyl diphosphate; HDR, (E)-4-hydroxy-3-methylbut-2-enyl diphosphate reductase; HDS, (E)-4-hydroxy-3-methylbut-2-enyl diphosphate synthase; HMBPP, (E)-4-hydroxy-3-methylbut-2-enyl diphosphate; HMG-CoA, 3-hydroxy-3-methylglutaryl-CoA; HMGR, HMG-CoA reductase; HMGS, HMG-CoA synthase; IDI, isopentenyl diphosphate isomerase; IPP, isopentenyl diphosphate; MCT, 2-C-methyl-d-erythritol 4-phosphate cytidylyltransferase; MDS, 2-C-methyl-d-erythritol 2,4 cyclodiphosphate synthase; ME-2,4cPP, 2-C-methyl-d-erythritol 2,4-cyclodiphosphate; MEP, 2-C-methyl-d-erythritol 4-phosphate; MVA, mevalonic acid; MVAP, mevalonate-5-phosphate; MVAPP, mevalonate-5-pyrophosphate; MVD, mevalonate diphosphate decarboxylase; MVK, mevalonate kinase; PMK, phosphomevalonate kinase; TPS, terpene synthase.

Figure 3

Functional genomic analyses were applied by the Plant Biotechnology Unit to determine how and when oil and toxins are produced in developing seeds and to identify possible impacts on the strategies for Jatropha genetic improvement.