1a.Objectives (from AD-416):
To develop transgenic lines overexpressing phenylpropanoid biosynthetic enzymes.
In year 1, we will assemble T-DNA transformation vectors to transgenic overexpression of phenylpropanoid metabolic genes in sorghum. In years 2 and 3, complete the transformation and characterization of these transgenic lines. This objective will provide transgenic lines that over-express all 10 gene products in sorghum monolignol biosynthesis for specific objectives 2-5.
1b.Approach (from AD-416):
To increase carbon flux through the phenylpropanoid pathway, we will introduce seven constitutive expression cassettes under control of the maize ubiquitin promoter. We will constitutively express the genes encoding 7 enzymes in the sorghum monolignol pathway: cinnamate 4-hydroxylase, 4-coumarate-CoA ligase, hydroxycinnamoyl CoA:shikimate/quinate transferase, caffeoyl CoA O-methyltransferase, ferulate 5-hydroxylase, caffeic acid O-methyltransferase and cinnamyl alcohol dehydrogenase in RTx430 sorghum. Agrobacterium-mediated transformation will be used coupled to npt II selectable marker. For each transgenic cassette a minimum of 10 independent events will be generated.
Seven expression cassettes containing genes involved in lignin biosynthesis were designed and constructed. The plant transformation experiments are nearly complete. These transgenic plants produced from these experiments will be used to study how modifying a critical biochemical pathway, lignin synthesis, will affect susceptibility of sorghum plants to insect pests and fungal pathogens that cause significant crop losses. Resulting information will be critical for deployment decisions of sorghum and other bioenergy grasses, because lignin is a major target for bioenergy crop improvement.