Development of SCAR marker specific to non-toxic Jatropha curcas L. and designing a novel multiplexing PCR along with nrDNA ITS primers to circumvent the false negative detection

Identification and validation of SNP markers linked to seed toxicity in Jatropha curcas L

Edible/non-toxic varieties of Jatropha curcas L. are gaining increasing attention, providing both oil as biofuel feedstock or even as edible oil and the seed kernel meal as animal feed ingredient. They are a viable alternative to the limitation posed by the presence of phorbol esters in toxic varieties. Accurate genotyping of toxic/non-toxic accessions is critical to breeding management. The aim of this study was to identify SNP markers linked to seed toxicity in J. curcas. For SNP discovery, NGS technology was used to sequence the whole genomes of a toxic and non-toxic parent along with a bulk of 51 toxic and 30 non-toxic F₂ plants. To ascertain the association between SNP markers and seed toxicity trait, candidate SNPs were genotyped on 672 individuals segregating for seed toxicity and two collections of J. curcas composed of 96 individuals each. In silico SNP discovery approaches led to the identification of 64 candidate SNPs discriminating non-toxic and toxic samples. These SNPs were mapped on Chromosome 8 within the Linkage Group 8 previously identified as a genomic region important for phorbol ester biosynthesis. The association study identified two new SNPs, SNP_J22 and SNP_J24 significantly linked to low toxicity with R² values of 0.75 and 0.54, respectively. Our study released two valuable SNP markers for high-throughput, marker-assisted breeding of seed toxicity in J. curcas.

Production of (Z)-11-(heptanoyloxy)undec-9-enoic acid from ricinoleic acid by utilizing crude glycerol as sole carbon source in engineered Escherichia coli expressing BVMO-ADH-FadL

Production of (Z)-11-(heptanoyloxy)undec-9-enoic acid from recinoleic acid was achieved by whole-cell biotransformation by Escherichia coli, utilizing crude glycerol as the sole carbon source. Whole-cell biotransformation resulted in ∼93% conversion of the substrate ricinoleic acid to (Z)-11-(heptanoyloxy)undec-9-enoic acid. We replaced the inducer-dependent promoter system (T7 and Rhm promotors) with a constitutive promoter system. This resulted in successful expression of ADH, FadL, and E6-BVMO, without costly inducer addition. Efficacy evaluation of the whole-cell biotransformation by inducer-free system by five different E. coli strains revealed that the highest product titer was accumulated in E. coli BW25113 strain. The engineered inducer-free system using crude glycerol as the sole carbon source showed competitive performance with induction systems. Optimized conditions resulted in the accumulation of 7.38 ± 0.42 mM (Z)-11-(heptanoyloxy)undec-9-enoic acid, and when 10 mM substrate was used as feed concentration, the product titer reached 2.35 g/L. The inducer-free construct with constitutive promoter system that this study established, which utilizes the waste by-product crude glycerol, will pave the way for the economic synthesis of many industrially important chemicals, like (Z)-11-(heptanoyloxy)undec-9-enoic acid.

DNA methylation and methylation polymorphism in ecotypes of Jatropha curcas L. using methylation-sensitive AFLP markers

We investigated DNA methylation and polymorphism in the methylated DNA using AFLP based methylation-sensitive amplification polymorphism (MS-AFLP) markers in ecotypes of Jatropha curcas L. growing in similar and different geo-ecological conditions. Three ecotypes growing in different geo-ecological conditions with environmental heterogeneity (Group-1) and five ecotypes growing in similar environmental conditions (Group-2) were assessed. In ecotypes growing in group-1, 44.32 % DNA was methylated and of which 93.59 % DNA was polymorphic. While in group-2, 32.27 % DNA was methylated, of which 51.64 % DNA was polymorphic. In site 1 and site 2 of group-1, overall methylation was 18.94 and 22.44 % respectively with difference of 3.5 %, while overall polymorphism was 41.14 and 39.23 % with a difference of 1.91 %. In site 1 and site 2 of group-2, overall methylation was 24.68 and 24.18 % respectively with difference of 0.5 %, while overall polymorphism was 12.19 and 12.65 % with a difference of 0.46 %. The difference of methylation percentage and percentage of methylation polymorphism throughout the genome of J. curcas at site 1 and 2 of group-1 is higher than that of J. curcas at site 1 and 2 of group-2. These results correlated the physico-chemical properties of soil at these sites. The variations of physico-chemical properties of soil at Chorwadla (site 1 in group-1 and site 2 in group-2) compared to the soil at Brahmapur (site 2 in group-1) is higher than that of soil at Neswad (site 1 in group-2). The study suggests that these homologous nucleotide sequences probably play important role in ecotype adaptation to environmental heterogeneity by creating epiallelic variations hence in evolution of ecotypes/clines or forms of species showing phenotypic/genotypic differences in different geographical areas.

Start codon targeted (SCoT) polymorphism in toxic and non-toxic accessions of Jatropha curcas L. and development of a codominant SCAR marker

Thirty six start codon targeted (SCoT) primers were used for characterization of 48 accessions of Jatropha curcas from different countries and include material with genetic variation for levels of phorbol esters, yield, seed oil content, test weight and plant type. SCoT analysis revealed high polymorphism and 74% of the primers generated polymorphic profiles. The SCoT6 primer discriminated edible and toxic accessions in a single reaction while the SCoT26 and 27 primers produced amplicons specific to toxic and non-toxic accessions, respectively. The polymorphic SCoT markers obtained with these three primers were converted to sequence characterized amplicon regions (SCARs) which resulted in codominant SCARs with SCoT6 primer and dominant SCARs with SCoT 26 and 27 primers. The codominant nature of SCoT6 primer and the resultant SCAR6 primer were validated on intraspecific hybrids derived from a cross between non-toxic and toxic accessions. The accession JP38 from Madagascar was found to be distinct and showed accession specific bands with 9 different SCoT primers. Sequence analysis of polymorphic amplicons obtained with SCoT6 primer showed a 65 bp deletion in accessions with low/zero phorbol esters. Diversity analysis separated the toxic and non-toxic accessions into two groups and the accessions JP29 and JP48 from Mexico formed a third cluster.