title: Characterisation of the willow phenylalanine ammonia-lyase (PAL) gene family reveals expression differences compared with poplar.
abstract: Willow is an important biomass crop for the bioenergy industry, and therefore optimal growth with minimal effects of biotic and abiotic stress is essential. The phenylpropanoid pathway is responsible for the biosynthesis of not only lignin but also of flavonoids, condensed tannins, benzenoids and phenolic glycosides which all have a role in protecting the plant against biotic and abiotic stress. All products of the phenylpropanoid pathway are important for the healthy growth of short rotation cropping species such as willow. However, the phenylpropanoid pathway in willow remains largely uncharacterised. In the current study we identified and characterised five willow phenylalanine ammonia-lyase (PAL) genes, which encode enzymes that catalyse the deamination of l-phenylalanine to form trans-cinnamic acid, the entry point into the phenylpropanoid pathway. Willow PAL1, PAL2, PAL3 and PAL4 genes were orthologous to the poplar genes. However no orthologue of PAL5 appears to be present in willow. Moreover, two tandemly repeated PAL2 orthologues were identified in a single contig. Willow PALs show similar sub-cellular localisation to the poplar genes. However, the enzyme kinetics and gene expression of the willow PAL genes differed slightly, with willow PAL2 being more widely expressed than its poplar orthologues implying a wider role for PALs in the production of flavonoids, condensed tannins, benzenoids, and phenolic glycosides, in willow.
authors.affiliation: AgroEcology Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom. Electronic address: femke.dejong@rothamsted.ac.uk.
authors.forename: Femke
authors.initials: F
authors.lastname: de Jong
authors.affiliation: AgroEcology Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom. Electronic address: steve.hanley@rothamsted.ac.uk.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Hanley
authors.affiliation: Plant Biology and Crop Sciences Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom. Electronic address: mike.beale@rothamsted.ac.uk.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Beale
authors.affiliation: AgroEcology Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom. Electronic address: angela.karp@rothamsted.ac.uk.
authors.forename: Angela
authors.initials: A
authors.lastname: Karp
mesh_terms: D003066:Coenzyme A Ligases / Q000378:metabolism; D005419:Flavonoids / Q000096:biosynthesis; D007527:Isoenzymes; D008031:Lignin / Q000378:metabolism; D015394:Molecular Structure; D010649:Phenylalanine / Q000378:metabolism; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000201:enzymology* / Q000235:genetics; D031308:Salicaceae / Q000201:enzymology / Q000235:genetics; D032108:Salix / Q000201:enzymology* / Q000235:genetics; D050564:Trans-Cinnamate 4-Monooxygenase / Q000378:metabolism
chemical_list: D005419:Flavonoids; D007527:Isoenzymes; D010649:Phenylalanine; D008031:Lignin; D050564:Trans-Cinnamate 4-Monooxygenase; D010650:Phenylalanine Ammonia-Lyase; D003066:Coenzyme A Ligases; C019943:4-coumarate-CoA ligase
keywords: Enzyme kinetics; Gene expression; Gene family; Phenylpropanoid metabolism; Salix viminalis (willow); Subcellular localisation; l-Phenylalanine ammonia-lyase (PAL)