Suppression subtractive hybridization reveals differential gene expression in sunflower grown in high P.

Sunflower (Helianthus annuus L.) is a commercially important oilseed crop. Previous studies proved that this crop is a promising plant species for phytoextraction of excess soil phosphorus (P) because of its superior P accumulating characteristics. Suppression subtractive hybridization (SSH) strategy was employed to isolate and characterize genes that are induced in response to high P in this crop. SSH library was prepared using cDNA generated from plants treated with high P as the 'tester'. Based on the results of dot blot analysis, 360 positive cDNA clones were selected from the SSH library for sequencing. A total of 89 non-redundant expressed sequence tags (ESTs) were identified as high P-responsive genes and they were classified into 6 functional groups. Several genes involved in metabolism showed markedly preferential expression in the library. For further confirmation, thirteen of the representative ESTs were selected from all categories for RT-PCR analysis and the results showed up-regulation of these genes in response to high P-treatment. The gene expression data derived from this study suggested that several of the up-regulated genes identified under high P-treatment might be involved in P-accumulation and tolerance in this plant.