• DOI:10.1038/nplants.2016.50
• Corpus ID: 3462127

Role of bifunctional ammonia-lyase in grass cell wall biosynthesis

@article{Barros2016RoleOB,
  title={Role of bifunctional ammonia-lyase in grass cell wall biosynthesis},
  author={Jaime Barros and Juan Carlos Serrani-Yarce and Fang Chen and David Baxter and Barney J. Venables and Richard A. Dixon},
  journal={Nature Plants},
  year={2016},
  volume={2}
}

• J. Barros, J. C. Serrani-Yarce, +3 authors R. Dixon
• Published 9 May 2016
• Biology
• Nature Plants

L-Phenylalanine ammonia-lyase (PAL) is the first enzyme in the biosynthesis of phenylpropanoid-derived plant compounds such as flavonoids, coumarins and the cell wall polymer lignin. The cell walls of grasses possess higher proportions of syringyl (S)-rich lignins and high levels of esterified coumaric acid compared with those of dicotyledonous plants, and PAL from grasses can also possess tyrosine ammonia-lyase (TAL) activity, the reason for which has remained unclear. Using phylogenetic, transcriptomic and in vitro biochemical analyses, we identified a single homotetrameric bifunctional ammonia-lyase (PTAL) among eight BdPAL enzymes in the model grass species Brachypodium distachyon. 13C isotope labelling experiments along with BdPTAL1-downregulation in transgenic plants showed that the TAL activity of BdPTAL1 can provide nearly half of the total lignin deposited in Brachypodium, with a preference for S-lignin and wall-bound coumarate biosynthesis, indicating that PTAL function is linked to the characteristic features of grass cell walls. Furthermore, isotope dilution experiments suggest that the pathways to lignin from L-phenylalanine and L-tyrosine are distinct beyond the formation of 4-coumarate, supporting the organization of lignin synthesis enzymes in one or more metabolons.