Natarajan et al. BMC Genomics 2010, 11:606 http://www.biomedcentral.com/1471-2164/11/606 R E S E A R C H A R T I C L E Open Access Gene discovery from Jatropha curcas by sequencing of ESTs from normalized and full-length enriched cDNA library from developing seeds Purushothaman Natarajan, Deepa Kanagasabapathy, Gnanasekaran Gunadayalan, Jasintha Panchalingam, Noopur shree, Priyanka Annabel Sugantham, Kavita Kumari Singh, Parani Madasamy* Abstract Background: Jatropha curcas L. 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 from J. curcas by large scale sequencing of expressed sequence tags (ESTs). Results: A normalized and full-length enriched cDNA library was constructed from developing seeds of J. curcas. The cDNA library contained about 1 × 106 clones 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 of J. curcas for 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. Background Jatropha curcas L., one of the 175 species in genus Jatropha of the family Euphorbiaceae is a perennial small tree or large shrub native to tropical America and is distributed throughout the tropics and subtropics of Asia and Africa [1]. Recently, jatropha oil is promoted as alternative transport fuel which can be directly blended with petro-diesel or transesterified with * Correspondence: hod.gn@ktr.srmuniv.ac.in Genomics Laboratory, Department of Genetic Engineering, SRM University, Chennai, Tamil Nadu, 603 203 India methanol and used as biodiesel. From a global food security point of view, jatropha being a non-edible crop which can be grown in areas not suitable for agriculture, is a preferred source for biodiesel feedstock as it does not compete with production of food crops. It reduces the dependence on fossil fuel which is often imported by using precious foreign currency. Its decentralized production will provide income for a large number of small and marginal farmers. Biodiesel is also less harm- ful to the environment in that its production and com- bustion reduces emission of greenhouse gases by 41% relative to fossil fuel [2]. It is reported that biodiesel © 2010 Natarajan et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.