Figure 9.

Model for the effects of altered chlorophyll synthase expression on tocopherol concentrations in Arabidopsis leaves. As indicated, HPT, which catalyzes the initial reaction in tocopherol biosynthesis, competes for the PDP substrate with chlorophyll synthase. Based on results from RNAi and cosuppression lines, reduced expression of CHLSYN increases PDP concentrations for HPT, leading to enhanced tocopherol production in Arabidopsis leaves (A). Conversely, based on results from overexpression lines, increased expression of CHLSYN decreases PDP concentrations for HPT, leading to reduced tocopherol production in Arabidopsis leaves (B).