TALEN-Mediated Mutagenesis of Large Number of COMT Copies in Sugarcane

Sugarcane is the world's most efficient feedstock for commercial production of bioethanol. In previous studies, RNAi suppression of the lignin biosynthetic gene, caffeic acid O-methyltransferase (COMT) have improved ethanol production from lignocellulosic biomass. However, sugarcane's highly polyploid genome presents quite a challenge for genetic modification techniques. Baskaran Kannan of University of Florida in the US targeted COMT with a single pair of Transcription Activator-Like Effector Nuclease (TALEN) for multi-allelic mutagenesis to modify lignin biosynthesis in sugarcane.

COMT mutants showed up to 19.7% lignin reduction and had significantly improved saccharification efficiency. Biomass production of COMT mutant lines with superior saccharification efficiency also did not differ significantly from the original cultivar under replicated field conditions.

Analysis revealed that mutations in 107 of the 109 COMT copies in the progeny of mutant lines using a single TALEN pair. The mutant line combined altered cell wall composition and greatly improved saccharification efficiency with good agronomic performance.

This study confirms the feasibility of mutating a very large number of target alleles for improvement of crops with complex genomes.

For more on this study, read the article in Plant Biotechnology Journal.