The Expression Of Key Enzyme Genes In Paclitaxel Synthesis Of Japanese Yew Seedlings Under Different Light Conditions

Five-year-old Japanese yew seedlings were taken as experimental materials to study the expression in different time scales of five key enzyme genes (geranylgeranyl pyrophosphate synthase gene, GGPPs; taxadiene synthase gene, TASY; taxadiene 5a hydroxylase gene, T5aH; phenylalanine aminomutase gene, PAM; 3’-N-debenzoyl-2-deoxytaxol-N-benzoyltransferase gene, DBTNBT) in paclitaxel biosynthesis under three different light conditions, including 30% of full light,60% of full light and 100% of full light. To provide a theoretical basis for the relationship between the key enzyme genes expression in paclitaxel biosynthesis and the paclitaxel content.(1) The results under diurnal changes scale from 6:00 to next day 6:00:The gene of GGPPs and T5aH expression changes were had the similar trends. The genes under 30% light condition was reached the peak value at 18:00, that under 60% light condition was reached the peak value at 14:00 and then reduced gradually. The former were 1.4 times and 1.8 times of the latter. The gene of TASY expression under 30% and 60% light were both reached the high level at 18:00, the latter was 1.3 times of the former. The gene of DBTNBT expression under 30% and 60% light were both reached the high level at 14:00, the former was 1.7 times of the latter. The gene expression level of PAM under 30% and 60% light conditions were similar and the expression under the two light conditions were reached the peak value at 18:00 and 10:00 respectively, but the whole expression level was low. The five genes under 100% light condition were all in the low expression level. The relative expression level under 100% light condition was less than 1. In a word, TASY gene was response to the highest degree under the three light conditions and the expression level was also the highest, the expression level of GGPPs, T5aH and DBTNBT genes were inhibited by different levels under the 60% light condition.(2) The results under monthly changes scale from July 17th to August 23rd:Under 30% light condition, the expression level of TASY gene which was in the highest expression level of the diurnal variation was still the highest more than a month later and was 3.7 times of the peak value in the diurnal variation.The followed were GGPPs, T5aH and DBTNBT genes, the expression level was 3.7 times,5.7 times and 10.7 times of the peak value in the diurnal variation respectively. The expression of PAM gene was still in the lowest level after a month. Under 60% light condition, the expression of four genes except PAM gene were fluctuated greatly during the month, the expression level was in the valley in July 17th and August 4th. The expression level of TASY gene was still the highest more than a month later and was 1.9 times of the peak value in the diurnal variation. The followed were T5aH, DBTNBT and GGPPs genes, the expression level was 16.1 times,20.1 times and 3.4 times of the peak value in the diurnal variation respectively. The expression of PAM gene was still in the lowest level after a month. Under 100% light condition, the expression level of five genes was lower than that under the 30% and 60% light conditions after a month. The gene of TASY expression was reached the peak value in July 26th and the value was 404.8, the gene of DBTNBT expression peak value was 136.5. The gene of GGPPs, T5aH, PAM expression peak value were 55.6,35.2,6.7.Overall, TASY gene was response to the highest degree and PAM gene was response to the lowest degree under the three light conditions. The expression level of five genes during the monthly changes were higher than the expression level of the genes during the diurnal variation of the same light conditions.