Controlled silencing of 4-coumarate:CoA ligase alters lignocellulose composition without affecting stem growth

Many bioenergy feedstocks are not easily converted to fermentable substrates due to of high proportions of lignin, which impedes the degradation of cell wall polysaccharides to fermentable sugars. To reduce lignin levels during plant growth, we generated transgenic Arabidopsis plants that contain a gene that confers inducible silencing of both 4CL1 and 4CL2 genes; these genes play a compensatory role in normal development of Arabidopsis, including in mechanisms of stem growth. To alter lignocellulose composition at specific times in plant development, genes were silenced at bolting, immature stages (5-7 cm high), and intermediate stages (10-15 cm high). The stems of induced plants at all stages of development exhibited increased cellulose content and reduced amounts of total lignin when compared with non-induced stems. Furthermore, treating plants at advanced stages of development (the immature and intermediate stages) had little impact on plant growth and development while plants treated at the bolting stage exhibited modest abnormal development. Our results suggest that it is possible to alter lignocellulose composition in plants without negative effects on plant growth.