Construction and characterization of a full-length cDNA library and identification of genes involved in salinity stress in wild eggplant (Solanum torvum Swartz)

The objectives of this paper were to construct a full-length cDNA library and to isolate genes that confer salt tolerance from the leaves of salinity-tolerant wild eggplant variety, 'Torvum Vigor' (Solanum torvum Swartz). A full-length cDNA library from the leaves was successfully constructed by a switching mechanism at 5'-end of RNA transcript (SMART) approach and a long-distance PCR (LD-PCR) technique. The titer of the primary cDNA library was 3.6 × 10∨6 cfuㆍmL-¹ and that of the amplified library was 1.2 × 10∨10 cfuㆍmL-¹ Gel electrophoresis results showed that most of the cDNA inserts ranged from 0.40 to 2.5 kb, with a recombination rate of 99%. A total of 427 randomly selected positive clones were sequenced. After removing the unsuccessful reads, 364 datasets were obtained and have been submitted to the NCBI Nucleotide Sequence Database under GenBank accession numbers JK265131-JK265494. Among the 364 submitted sequences, 74.45% of them contained full-length coding regions. BLASTX analysis revealed that 62.36% of the 'Torvum Vigor' expressed sequence tags (ESTs) possessed homology to known or putative proteins of other organisms. Seven genes that might be responsible for the encoding of known proteins in other organisms were identified to confer salt tolerance. This evidence demonstrated that the cDNA library constructed was a full-length library of high quality. It could be a useful resource for further research in the cloning of stress-related genes, which could be utilized in the genetic improvement of vegetable crops using transgenic technology.