Identification of low-light induced genes in cucumber (Cucumis sativus) seedlings by suppression subtractive hybridization

Cucumber is one of the most important vegetables that are very sensitive to low-light stress. The specific mechanism involved is poorly understood. Here we investigate the expression profile of genes induced by low-light stress in Cucumis sativus seedlings with suppression subtractive hybridization (SSH). cDNA prepared from cucumber seedlings treated with 100 μmol m⁻² s⁻¹ light intensity as testers and cDNA from unstressed cucumber seedlings with 800 μmol m⁻² s⁻¹ light intensity as drivers. A forward subtractive cDNA library was constructed, from which 768 recombinant colonies were picked and amplified. Through differential screening of the subtractive cDNA library, 246 clones were identified as low-light stress induced. After sequencing, 64 unique expressed sequence tags (ESTs) were obtained by clustering and blast analysis, which included some functionally unknown transcripts. Of the 64 ESTs, 50 ESTs identity to their homolog in GenBank, 14 ESTs were expected to be novel genes. The ESTs with significant protein homology were sorted into 16 groups according to the functional categories of the Arabidopsis proteins.