Identification of differentially expressed genes in dormant (banjhi) bud of tea (Camellia sinensis (L.) O. Kuntze) using subtractive hybridization approach.

Growth regulation associated with dormancy is an essential element in plant's life cycle that leads to changes in expression of large number of genes. Forward and reverse suppression subtractive hybridization (SSH) libraries were developed to identify and characterize the genes associated with bud (banjhi) dormancy in tea (Camellia sinensis (L.) O. Kuntze). Efficiency of subtraction was confirmed by comparing the abundance of β-actin gene. A total of 17 and 45 unique sequences were obtained from forward and reverse SSH library respectively. Many of the differentially regulated genes have unknown (41.1% and 26.7%) or hypothetical functions (11.7% and 2.2%) in forward and reverse SSH library respectively, while others have a role in cell growth and metabolism. Further, semi-quantitative RT-PCR was carried out for selected genes to validate the quality of ESTs from SSH library. Gene Ontology analysis identified a greater association of these ESTs in cellular metabolic pathways and their relevance to bud dormancy. Based on the EST data, the putative role of identified genes from tea is discussed in relation to dormancy, which includes various metabolic and signalling pathways. We demonstrated that SSH is an efficient tool for enriching up- and down-regulated genes related to bud dormancy in tea. This study represents an attempt to investigate banjhi dormancy in tea under field conditions, and the findings indicate that there is a potential to develop new approaches to modulate dormancy in this species.