The peanut (Arachis hypogaea L.), also known as the groundnut, is an important oilseed crop in the tropical and subtropical regions of the world. It is grown on six continents but mainly in Asia, Africa and America. Peanuts are cultivated on 23.51 million hectares worldwide, with a total global production of approximately 35.52 million tons (the weight includes the shell). China is the largest producer in the world, accounting for 37.6% (13.34 million tons) of the total world production (FAO, 2009, http://faostat.fao.org).
Peanuts have a desirable fatty acid profile and are rich in vitamins, minerals and bioactive materials, including several known heart-healthy nutrients, such as monounsaturated and polyunsaturated fatty acids, potassium, magnesium, copper niacin, arginine, fibre, α-tocopherol, folates, phytosterols, and flavonoids. Indeed, peanut consumption has been associated with an improvement in the overall quality of the diet and nutrient [1–4].
In China, almost 60% of the peanuts are used to produce peanut oil . Peanut oil, due to its high monounsaturated fat content, is considered healthier than saturated oils and is resistant to rancidity. Monounsaturated fat, much of which is oleic acid, is a healthy type of fat that has been implicated in the health of skin  and has been demonstrated to reduce cardiovascular disease risk and/or risk factors in both epidemiological and clinical studies [1, 2, 7].
The development of the peanut seed has been studied intensely to understand the physiological, biochemical, and molecular characteristics that determine the oil quality and their beneficial nutritional contributions. However, the development of the peanut seed is a complex process involving a cascade of biochemical changes, which involve the transcriptional modulation of many genes, yet little is known about these transcriptional changes and their regulation. To date, little research in this area has been reported. Bi  developed a seed cDNA library for the peanut to analyse gene expression levels during seed development, and 17,000 expressed sequence tags (ESTs) were sequenced and used for microarray analysis. Recently, the development of next-generation high-throughput DNA sequencing technology has provided a novel method for both mapping and quantifying transcriptomes (RNA-seq) . RNA-seq technology has been successfully applied quite ubiquitously to species such as humans, yeast, mice, grape, Arabidopsis, rice, soybeans, sesame, and sweetpotato [9–19]. Moreover, RNA-seq data are highly reproducible, with few systematic discrepancies among technical replicates . The latest paired-end tag sequencing strategy of RNA-seq further improves the DNA sequencing efficiency and expands short-read lengths, providing a better depiction of transcriptomes . Transcriptomic information is used in a wide range of biological studies and provides fundamental insight into biological processes and applications, such as the levels of gene expression , the gene expression profiles during development [13, 17] or after experimental treatments , gene discovery , SSR mining [10, 11, 25], and SNP discovery [12, 25–27]. However, transcriptomic information is lacking for the peanut plant because this information is difficult to obtain and, to date, there has been little interest in such data.
Chen  reported that the accumulation of seed oil in peanuts could be divided into three stages based on phenotype, namely, the initial accumulation stage, the fast accumulation stage and the steady accumulation stage. As we are interested in identifying genes that are expressed in the seed during the fast accumulation period, we carried out a global analysis of the peanut transcriptome during seed development using the Illumina RNA-seq method. We also present an overview of the RNA-seq data for the peanut as a potential model for future RNA-seq analyses and to establish a biotechnological platform for peanut research.