Jatropha curcas L. is an important non-edible oilseed crop with promising future in biodiesel production. However, factors like oil yield, oil composition, toxic compounds in oil cake, pests and diseases limit its commercial potential. Well established genetic engineering methods using cloned genes could be used to address these limitations. Earlier, 10,983 unigenes from Sanger sequencing of ESTs, and 3,484 unique assembled transcripts from 454 pyrosequencing of uncloned cDNAs were reported. In order to expedite the process of gene discovery, we have undertaken 454 pyrosequencing of normalized cDNAs prepared from roots, mature leaves, flowers, developing seeds, and embryos of J. curcas.

Background: Jatropha curcasL. is promoted as an important non-edible biodiesel crop worldwide. Jatropha oil, which is a triacylglycerol, can be directly blended with petro-diesel or transesterified with methanol and used as biodiesel. Genetic improvement in jatropha is needed to increase the seed yield, oil content, drought and pest resistance, and to modify oil composition so that it becomes a technically and economically preferred source for biodiesel production. However, genetic improvement efforts in jatropha could not take advantage of genetic engineering methods due to lack of cloned genes from this species. To overcome this hurdle, the current gene discovery project was initiated with an objective of isolating as many functional genes as possible fromJ. curcasby large scale sequencing of expressed sequence tags (ESTs).Results: A normalized and full-length enriched cDNA library was constructed from developing seedsof J. curcas. The cDNA library contained about 1 × 10⁶clones and average insert size of the clones was 2.1 kb. Totally 12,084 ESTs were sequenced to average high quality read length of 576 bp. Contig analysis revealed 2258 contigs and 4751 singletons. Contig size ranged from 2-23 and there were 7333 ESTs in the contigs. This resulted in 7009 unigenes which were annotated by BLASTX. It showed 3982 unigenes with significant similarity to known genes and 2836 unigenes with significant similarity to genes of unknown, hypothetical and putative proteins. The remaining 191 unigenes which did not show similarity with any genes in the public database may encode for unique genes. Functional classification revealed unigenes related to broad range of cellular, molecular and biological functions. Among the 7009 unigenes, 6233 unigenes were identified to be potential full-length genes.Conclusions: The high quality normalized cDNA library was constructed from developing seeds ofJ. curcasfor the first time and 7009 unigenes coding for diverse biological functions including oil biosynthesis were identified. These genes will serve as invaluable genetic resource for crop improvement in jatropha to make it an ideal and profitable crop for biodiesel production.

DNA barcoding is a desirable tool for medicinal product authentication. DNA barcoding is a method for species identification using short DNA sequences that are conserved within species, but variable between species. Unlike animals, there is no single universal DNA barcode locus for plants. Coding markers, matK and rbcL, and noncoding markers, trnH-psbA (chloroplast) and ITS2 (nuclear), have been reported to be suitable for the DNA barcoding of plants with varying degree of success. Sixty-four accessions from 20 species of the medicinal plant Cassia were collected, and analyzed for these 4 DNA barcoding markers. PCR amplification was 100% successful for all 4 markers, while intra-species divergence was 0 for all 4 Cassia species in which multiple accessions were studied. Assuming 1.0% divergence as the minimum requirement for discriminating 2 species, the 4 markers could only differentiate 15 to 65% of the species studied when used separately. Adding indels to the divergence increased the percentage of species discrimination by trnH-psbA to 90%. In 2-locus barcoding, while matK+rbcL (which is recommended by Consortium for the Barcoding of Life) discriminated 90% of the species, the other combinations of matK+ITS and rbcL+trnH-psbA showed 100% species discrimination. However, matK is plagued with primer issues. The combination of rbcL+trnH-psbA provided the most accurate (100% species ID) and efficient tiered DNA barcoding tool for the authentication of Cassia medicinal products.

Swarna is a popular cultivated indica rice variety with low glycemic index (GI) but its genetic basis is not known. The whole genome of Swarna was sequenced using Illumina’s paired-end technology and the reads were mapped to the Nipponbare reference genome. Overall, 65,984 non-synonymous SNPs were identified in 20,350 genes and in silico analysis predicted that 4,847 of them in 2,214 genes may have deleterious effect on protein functions. Polymorphisms were found in all the starch biosynthesis genes, except the gene for branching enzyme IIa. It was found that T/G SNP at position 246, ‘A’ at position 2,386 and ‘C’ at position 3,378 in the granule bound starch synthase I gene and C/T SNP at position 1,188 in the glucose-6-phosphate translocator gene may contribute to the low GI phenotype in Swarna. All these variants were also found in the genome of another low GI indica rice variety from Columbia, Fedearroz 50. The whole genome analysis of Swarna helped to understand the genetic basis of GI in rice, which is a complex trait involving multiple factors.