Expression of sesquiterpene synthase genes in different sunflower tissues. (a) RT-PCR analyses of germacrene A synthases, HaCS, farnesyl diphosphate synthase, and ubiquitin gene expression. Total RNA was extracted from roots (R), stems (S), cotyledons (C), young leaves (YL), old leaves (OL), ray flowers (RF), and capitate glandular trichomes (T). The constitutively expressed gene for ubiquitin was used as cDNA loading control and internal standard. Due to high sequence similarity differentiation between HaGAS1 and HaGAS2 was not possible by PCR. (b) Detection of the expressed genes for HaGAS1 and HaGAS2 in trichomes (left) and roots (right) by selective restriction digestion of full length HaGAS1/2 cDNA (◂). HaGAS1 contains a PauI but no DraI recognition site while HaGAS2 contains a DraI site but no PauI recognition site.DraI specifically cuts the amplicon of HaGAS1 (1680 bp) into a 1406 bp (•) and 274 bp (▪) fragment. PauI specifically cuts the 1680 bp HaGAS2 amplicon into 1105 (*) and 575 bp (+) fragments. ND: undigested control. L: marker.