Fig. 4: Grasses have a feedback insensitive DHS1b enzyme that is expressed in internodes.

a Phylogeny of plant DHS proteins (outgroup: Marchantia polymorpha). Sequences highlighted in blue have been characterized in this study. Bootstrap test values (based on 1000 replications) below 50 have been omitted. Scale bar indicates number of amino acid substitutions per site. Species abbreviations not introduced in Fig. 3a include: Cucsa, Cucumis sativus; Gorai, Gossypium raimondii, GSMUA, Musa acuminata. b Expression patterns of Brachypodium DHS genes in different organs and developmental stages compared to BdTyrA1, BdPTAL, and other genes of the lignin pathway. Enzyme abbreviations: 4CL, 4-coumarate:CoA ligase; C3’H, 4-Coumarate 3-hydroxylase; COMT, caffeic acid/5-hydroxyferulic acid O-methyltransferase. c Inhibition of recombinant Brachypodium BdDHS1a, BdDHS1b, and BdDHS2 by 0.5 mM of aromatic amino acids. Data presented as the average of n = 3 replicates from three independent experiments; error bars = SD. d IC₅₀ determination curve of tryptophan inhibition in Brachypodium DHS1a (cyan, squares), DHS1b (purple, circles) and DHS2 (pink, triangles). Data presented as the average of n = 2 technical replicates e Effect of 0.5 mM of intermediates of AAA pathway(s) on Brachypodium DHSs. Data presented as the average of n = 3 replicates from three independent experiments; error bars = SD. f IC₅₀ determination curve of arogenate inhibition in Brachypodium DHSs (figure legend as in d) Data presented as the average of n = 2 technical replicates. Source data for panels c–f are provided within the Source Data File.