Figure 1.
Illustration of floral mimicry produced by the pseudoflower-forming rust fungus Puccinia monoica.
(A) Picture of uninfected flowering Boechera stricta plant (left) and a close up picture of its light pink flowers (right). (B) Pictures of vegetative tissues of B. stricta plants that produce pseudoflowers upon infection with Puccinia monoica (left) and a close up of a yellow P. monoica pseudoflower (right). Samples from B. stricta (A) and pseudoflowers (B) were collected near Gunnison, Colorado, United States of America.
Figure 2.
Differentially expressed genes in pseudoflowers and uninfected Boechera stricta flowers using rank products (RP) analysis.
(A) Volcano plots showing changes in gene expression in Puccinia monoica-induced pseudoflowers (‘Pf’) vs. uninfected Boechera stricta plant stems and leaves (‘SL’). (B) Volcano plots showing changes in gene expression in uninfected B. stricta flowers (‘F’) vs. uninfected B. stricta stems and leaves (‘SL’). Each point in the volcano plot represents changes in gene expression from a single Arabidopsis thaliana gene. Red points indicate genes that are significantly up or down-regulated with a RP FDR value < 0.05. X-axis correspond the log2 ratio (‘Pf’/’SL’ or ‘F’/’SL’ comparison) and the y-axis correspond to the –log10 of RP FDR value. (C) Venn diagram showing number of genes that are differentially regulated specifically in ‘Pf’ vs. ‘SL’ and ‘F’ vs. ‘SL’ comparisons.
Figure 3.
qRT-PCR validation of differentially expressed genes in pseudoflowers.
Quantitative Real Time PCR (qRT-PCR) on a panel of seven genes was used to verify the transcriptional changes observed by microarray analysis. Consistent with the microarray results, expression of TEOSINTE BRANCHED1, CYCLOIDEA, and PCF TRANSCRIPTION FACTOR3 (TCP3, At1g53230), SUGAR TRANSPORTER1 (SWEET1, At1g21460), SUGAR TRANSPORTER15 (SWEET15, At5g13170) and TYROSINE TRANSAMINASE enzyme encoding gene (TT, At4g23590) genes was up-regulated in Puccinia monoica-induced pseudoflowers (‘Pf’) compared to B. stricta stems and leaves (‘SL’), while ALTERED MERISTEM PROGRAMMING1 (AMP1, At3g54720), KNOTTED-LIKE1 (KNAT1, At4g08150) and FLOWERING LOCUS T (FT, At1g65480) genes was down-regulated (see Table 1). In addition, SWEET15 and FT genes were confirmed to be down-regulated in uninfected B. stricta flowers (‘F’) compared to ‘SL’ as shown by microarray analysis (see Table S2). To indicate the mode of regulation we used two symbols: ‘*’ for significant up-regulation and ‘#’ for significant down-regulation. The number of symbols indicates level of significance: one for P < 0.05, two for P < 0.01 and three for P < 0.001. The error bars represents standard error of the mean.
Figure 4.
Overview of biological processes altered in pseudoflowers.
(A) Simplified gene ontology biological processes (GOBP) network showing processes enriched among genes with expression altered in Puccinia monoica-induced pseudoflowers (‘Pf’) compared to uninfected Boechera stricta stems and leaves (’SL’) and B. stricta flowers (‘F’) compared to ‘SL’. Node size with average GOBP fold induction (average of log2 ratios of all genes within a GOBP in ‘Pf’/’SL’ and ‘F’/’SL’, respectively) from green for average induction folds < 0 that indicates down-regulation to red for average induction folds > 0 that indicates up-regulation (node color). Some nodes and edges have been omitted for clarity. (B) Detailed GOBP network showing processes enriched among genes with expression altered in ‘Pf’ vs. ‘SL’. Genes highlighted in the text are indicated with diamonds connected to dashed lines to the processes they are involved in. This network shows same topology as in (A).
Figure 5.
Altered expression in pseudoflowers of genes involved in the biosynthesis of aromatic compounds.
(A) Down-regulation of genes involved in terpene (monoterpenes and sesquiterpenes) biosynthetic pathway: TERPENE SYNTHASE10 (TPS10, At2g24210) and 21 (TPS21, At2g23960). (B) Up-regulation of genes involved in phenylethanol biosynthetic pathway: TYROSINE TRANSAMINASE enzyme encoding gene (TT, At4g23590). Pathway diagrams were obtained from AraCyc and PlantCyc browsers (http://plantcyc.org/). Blocks represent genes involved in the production of particular compounds within the metabolic pathway. The color of the block indicates relative gene fold induction (from green for average induction folds < 0 that indicates down-regulation to red for average induction folds > 0 that indicates up-regulation) in Puccinia monoica-induced pseudoflowers (‘Pf’) compared to uninfected Boechera stricta stems and leaves (‘SL’).