Identification of differentially expressed sequences in bud differentiation of oriental hybrid lily cultivar ‘Sorbonne’ via suppression subtractive hybridization

Abstract

The developmental process of lily flower bud differentiation has been studied in morphology thoroughly, but the mechanism in molecular biology is still ambiguous and few studies on genetic expression have been carried out. Little is known about the physiological responses of flower bud differentiation in Oriental hybrid lily ‘Sorbonne’ (Lilium spp.) during the stages of flower bud differentiation and the genes involved in these responses. In this study, the differences in gene expression between two stages of lily bud differentiation: the stage before bud differentiation (SB) and the stage of bud differentiation (SD) were studied. The suppression subtractive hybridization (SSH) method conducted to generate large-scale expressed sequence tags (EST) was designed to identify gene candidates related to the morphological and physiological differences between the stage before bud differentiation and the stage of bud differentiation of lily. The results showed that the SD could induce differential expression of the genes related to lily flower bud differentiation. EST were isolated, cloned, sequenced and identified using BlastN and BlastX, and indicated that at the stage of the flower bud differentiation, there is an activation of a floral development response at a molecular level, mainly related to low temperature and post-transcriptional regulation of nucleic acids. 24.1% of the isolated sequences are not yet described which showed the lack of genomic information currently available for lily. Sequence analysis revealed that most of the differentially expressed genes are related to metabolism and regulation such as protein synthesis and catabolism of carbohydrate related to flower formation. Some genes also encoded transcription factors. These genes showed high mRNA transcript levels in the stage of flower bud differentiation. This study revealed that unknown genes are putatively involved in the stage of lily flower bud differentiation, which serve as a starting point for understanding the differentiation of lily flower bud.

Keywords: Lily flower bud differentiation, gene expression, suppression subtractive hybridization (SSH)