Barvkar et al. BMC Genomics 2012, 13:175 http://www.biomedcentral.com/1471-2164/13/175 Page 7 of 13 and seed developmental stages from fertilization to seed maturation. Eukaryotic translation initiation factor 5A (ETIF5A GenBank ID GR508912) was selected as a reference gene after confirming the stability of this gene across all the tissue types used in the study [17]. Single dissociation curves were observed for all the flax UGT genes and ETIF5A, confirming amplification specificity of the primers. The ΔCT method [18] was used to express the results relative to the reference gene. A validation experiment was conducted to ensure similar amplification efficiencies of all the genes analyzed. Relative transcript abundance of 10 flax UGT genes was profiled and is graphically represented in Figure 4. All the selected genes had EST expression evidence and covered six phylogenetic groups. The LuUGT71M1 transcript was detected in mature leaves, stem, etiolated seedling and 48 DAF; however, the relative expression level compared to other UGT genes was very low. LuUGT94G1 expressed constitutively in almost all tissues types; specifically it showed maximum expression in stem. Its expression was also supported by ESTs from stem peel library. LuUGT72N1 expressed in flower, 4 and 8 DAF with peak at 4 DAF. LuUGT85Q2 had 54 ESTs mapped from flower EST library and RT-qPCR analysis confirmed its high expression in flower. Expression of LuUGT89B3 was observed in later stages of seed development viz. 30 and 48 DAF and supported by two EST clones identified in torpedo seed coat stage. LuUGT72M2 expressed in ma- ture leaves, flowers and early seed developmental stages whereas LuUGT72R1 and LuUGT712B1 were highly expressed in various seed developmental stages. LuUGT85Q1 belonged to family 85 which is known to be involved in glycosylation of cyanogenic compounds [19]. The abundance of cyanogenic compounds and higher Figure 4 RT-qPCR expression profile of 10 selected flax UGT genes in 12 different tissue types. Tissue types analysed for LuUGT expression include; mature leaves (ML), stem (ST), root (RT), etiolated seedling (ES), flower (FL) and seed developmental stages (4, 8, 12, 16, 22, 30, 48 DAF). These graphs show the relative transcript abundance of each gene in comparison with the reference gene, Linum usitatissimum ETIF5A (GR508912). Expression values are reported as the average of three biological and two technical replicates. Values correspond to the mean and standard error of biological triplicates.