Fig. 1: Plants have several ways to produce indole.
From: A pseudoenzyme enables indole biosynthesis in eudicot plants
a, Occurrence of BXD-producing species and indole biosynthetic enzymes among plant families. Phylogenetic tree of plant families, based on the Kew Gardens tree of life dataset54. Plant families comprising BXD-producing species are colored in green. Types of IGP lyase enzymes present are indicated on the side. b, Indole as a precursor for BXDs is produced by BX1 in monocots and basal eudicots or, as reported here, by TSA–TSB-like complexes in core eudicots. BX2, BX3, BX4, BX5 and BX8 enzymes convert indole into the BXD HBOA-Glc and DIBOA-Glc. c, BX1 and TSB-like from different species provide indole as a precursor for BXDs. Bx1 genes from Z. mays and C. orientalis, TSA genes from L. galeobdolon and A. squarrosa, TSB-like genes from A. squarrosa, L. galeobdolon, P. trichocarpa, A. thaliana and N. benthamiana and the INS gene from A. thaliana were transiently expressed in N. benthamiana along with the BXD biosynthetic genes Bx2, Bx3, Bx4, Bx5 and Bx8 from Z. mays. The negative control (neg ctr) consisted of lines expressing only Bx2, Bx3, Bx4, Bx5 and Bx8. Bar graphs represent the mean ± s.d. for three independent biological replicates (n = 3 plants). Columns labeled with different letters represent statistically significant differences (P < 0.05, one-way analysis of variance (ANOVA) with Tukey’s correction for multiple comparisons). FW, fresh weight. d, AsTSB-like promotes the formation of indole. MRM showing indole accumulation upon transient expression of AsTSB-like or AsTSA in N. benthamiana. The chromatogram scale (y axis, peak intensity) is equalized across all chromatograms. e, AsTSA and AsTSB-like transiently expressed in N. benthamiana colocalize in the chloroplast. AsTSA–mCyan, AsTSB-like–eYFP and chloroplast autofluorescence are displayed. Left: larger sections of bright field images with superimposed fluorescence channels. Dashed box (top) indicates dimensions of bottom image. Dashed box (bottom) indicates dimensions of fluorescence images.
