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Figure 6 | BMC Research Notes

Figure 6

From: Expression level of a flavonoid 3′-hydroxylase gene determines pathogen-induced color variation in sorghum

Figure 6

Role of F3′H in the 3-deoxyanthocyanidin pathway. Flavonoid compounds share the same basic skeleton of a flavan nucleus consisting of two aromatic rings with six carbon atoms (rings A and B), which are interconnected by a heterocyclic ring with three carbon atoms (ring C). Flavanone 3′-hydroxylase (F3′H) introduces a hydroxyl group at the 3′ position of ring B of naringenin. Expression of F3′H thus adds the step that leads to the production of luteolinidin. The expression level of F3′H matches the color exhibited on the areas of each sorghum plant infected with Bipolaris sorghicola. High-level expression of F3′H may depend on the action of Tan1 transcription factor. Flavanone 3-hydroxylase (F3H) catalyzes C-3 hydroxylation of the C ring of naringenin, leading ultimately to anthocyanidin production. However, F3H was not expressed in the sorghum cultivars we studied (dotted arrow). Naringenin is the common intermediate for apigeninidin, luteolinidin, or the anthocyanidins.

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