Without the CHI gene, the single expression of the CHS, F3H,
and FLS genes were also not effective. The concomitant expression
of the 4 genes was required to increase the flavonol content
of the flesh (Colliver and others 2002). In northern blot analysis,
Muir and others (2001) detected no expression of endogenous
CHI in tomato flesh. However, onion CHI was amplified
by RT-PCR (Figure 2). Thus, ectopic expression of CHI produced
higher flavonol content in the flesh than diffusion from the
peel to the flesh. However, the increase in flavonol content in the
CHI transgenic tomato was significantly lower than in the flesh of
the Del/Ros1 transgenic tomatoes. Further experimentation with
other cultivars will be needed to explain this result. Differential
increases in flavonol content corresponding to different cultivars
were reported by Luo and others (2008) in transgenic tomatoes by
expressing AtMYB12, resulting in approximately twice as much
rutin and Kaempferol rutinoside in the Micro Tom cultivar compared
with the Money Maker cultivar. The difference in flavonol
content between wild-type cultivars was greater than that between
transgenic cultivars (Luo and others 2008).