Plant Direct

O_LIRationale: Xylem morphology in annual monocots is important for water use strategies in many agronomically important species. C_LIO_LIMethods: We assess how xylem perforation plates affect water use strategies in maize (Zea mays L.) through in silico modeling, empirical studies under water deficit in controlled environments, and in the field. C_LIO_LIKey Result: Significant genotypic variation for the prominence and frequency of perforation plates was observed in maize germplasm. Perforation plate phenotypes had high heritability, were associated with several QTL, and were pleiotropic across leaves, aerial nodal roots, and subterranean nodal roots. Perforation plate phenotypes did not affect vulnerability to cavitation, but modeling predicted that they should affect axial water transport, which was supported by in situ measurements of root segments. Metaxylem vessel length was correlated with the rate of root elongation, root depth, and deep-water utilization in mesocosms. Under drought stress in the field, variation in xylem vessel length was associated with leaf roll, leaf temperature, transpiration, photosynthesis, and grain yield. C_LIO_LIMain Conclusion: Phenotypic variation for xylem perforation plate phenotypes in maize directly affects axial water conductance and is part of a pleiotropic syndrome with greater root elongation and deeper rooting that improves adaptation to water deficit stress. C_LI

Epicuticular wax blooms are associated with improved drought resistance in many species, including Sorghum bicolor. While the role of wax in drought resistance is well known, we report new insights into how light and drought dynamically influence wax production. We investigated how wax quantity and composition are modulated over time and in response to different environmental stressors, as well as the molecular and genetic mechanisms involved in such. Gas chromatography-mass spectrometry and photographic results showed that sorghum leaf sheath wax load and composition were altered in mature plants grown under drought and simulated shade, though this phenomenon appears to vary by sorghum cultivar. We combined an in vitro wax induction protocol with GC-MS and RNA-seq measurements to identify a draft signaling pathway for wax bloom induction in sorghum. We also explored the potential of spectrophotometry to aid in monitoring wax bloom dynamics. Spec-trophotometric analysis showed primary differences in reflectance between bloom-rich and bloomless tissue surfaces in the 230-500nm range of the spectrum, corresponding to the blue color channel of photographic data. Our smartphone-based system detected significant differences in wax production between control and shade treatment groups, demonstrating its potential for candidate screening. Overall, our data suggest that wax extrusion can be rapidly modulated in response to light, occurring within days compared to the months required for the changes observed under greenhouse drought/simulated shade conditions. These results highlight the dynamic nature of wax modulation in response to varying environmental stimuli, especially light and water availability. Significance StatementAgricultural crops require significant freshwater for irrigation, making food security vulnerable to drought. Epicuticular wax blooms are associated with drought tolerance in many plants, including Sorghum bicolor. We investigated how environmental factors like light and drought influence wax production in sorghum. Wax production, composition, and gene expression were compared between sorghum exposed to different environmental stressors, reavealing dynamic modulation of wax production in response to environmental stress as well as signaling genes potentially involved in regulating wax production. These findings broaden our understanding of wax-related drought tolerance mechanisms, providing a foundation for future efforts to enginner crops with improved climate resilience.

Plant root systems provide critical functions to enable plant survival. From anchoring the plant in the soil to finding and acquiring water and nutrients, these organs are essential for plant productivity. Despite a variety of root functions, research typically focuses on defining only one function. In this study, we explore a trade-off hypothesis, that the optimization of one root function (i.e. anchorage) may negatively impact another root function (i.e. nitrogen uptake). Previous work has demonstrated that larger roots are stronger, but may also have a diminished capacity for nutrient acquisition due to a reduced surface area to volume ratio. Using maize brace roots that had entered the soil, we show here that larger roots are both stronger and take up more nitrogen. Despite this general relationship, there are subtle trade-offs between mechanics and uptake that occur when assessing individual genotypes. These trade-offs represent an opportunity to optimize one root function without compromising other root functions. Together these data demonstrate that our original trade-off hypothesis was incorrect for maize brace roots, and that larger roots are both stronger and take up more nitrogen.

Increasing the diversity of biofuel crops can help meet energy demands while also stabilizing the domestic biofuel market. Sorghum bicolor is a promising feedstock for bioethanol production due to its sugar accumulation and storage in the stem in addition to its cellulosic biomass. Sorghum also exhibits high tolerance to abiotic stresses like extreme temperatures and drought. However, sorghums sugar production falls short when compared to current bioethanol feedstocks like maize and sugarcane. Therefore, to improve sorghum for the bioethanol market, an autotetraploid sorghum line was induced using colchicine treatments to increase cell size for greater sugar production and storage. Induced autotetraploid sorghum lines were validated with flow cytometry and screened using stomatal prints to detect larger stomatal cells. Two separate autotetraploid sorghum lines that were derived from the same M1 plant were characterized and evaluated for sugar production in a two-year field trial. The two autotetraploid lines displayed equal or improved performance when compared to their diploid equivalents for multiple juicing traits. Altogether, the data illustrate sorghums tolerance for autopolyploidy induction in an inbred background and suggest an opportunity for further improvements through progressive heterosis. SIGNIFICANCE STATEMENTPolyploidy has played a significant role in the improvement of some crop species. The characterization of a novel autotetraploid sweet sorghum line demonstrates the potential of increased sugar production in polyploids for biofuel applications.

The Arabidopsis thaliana genome contains twenty genes that are analogous to mammalian ionotropic glutamate receptors. There are sixteen mammalian glutamate receptors, which are best known for their roles in neuroplasticity, learning, and memory. The large number of glutamate receptors in A. thaliana suggests they play important roles in the plants growth and development, possibly serving to regulate function like they do in non-excitable mammalian tissues. A specific glutamate receptor, GLR3.3, is highly expressed in root tissue of plants, and has been found to promote stronger, more coordinated curvature development during the process of gravitropism. Gravitropism is the ability of a plant to change its orientation to that of the gravity vector when displaced from its gravitational set point angle (GSPA). A previous association study identified six candidate genes which were correlated with the same phenotypic characteristics of gravitropism as GLR3.3. Utilizing real time RT-PCR (qRT-PCR) expression profiles were created for each candidate gene, including GLR3.3. A qRT-PCR method was developed to provide a more quantitative and sensitive way for measuring gene expression than traditional PCR methods. Furthermore, MIQE (Minimum Information for Publication of Quantitative Real-Time PCR Experiments) guidelines were followed to ensure data robustness. Expression profiles that were similar to GLR3.3 were hypothesized to be good candidates as cell signaling components of this novel pathway. This is the beginning of a process that will identify a GLR-dependent pathway, the role of this novel pathway in the gravitropic response, and the influence of GLRs in plant physiology.

Cotton (Gossypium hirsutum) is an economically important crop, but it faces increasing pest outbreaks, especially in non-irrigated areas. In this study, 20 cotton farms using center-pivot irrigation were sampled in southern Georgia to assess chemical differences between non-irrigated and irrigated areas. Proton (1H) nuclear magnetic resonance (NMR) data were obtained from cotton leaves, and Principal Component Analysis (PCA) was performed to assess differences in chemical composition. Across all samples, farm site accounted for most of the variability, but within each farm site, the PCA scores plots showed clear separation between non-irrigated and irrigated conditions in 10 sites. Inspecting the PCA loadings revealed significant resonances resembling a lipid-like signal. After reverse-phase fractionation, we observed that many of these resonances appeared together in later fractions, suggesting a lipid, specifically a fatty acid such as linoleic acid. We hypothesized that differences in net lipid saturation level may drive separation between non-irrigated and irrigated samples. Six farm sites had a significantly or marginally significantly higher degree of unsaturation in irrigated samples, while one farm site had significantly higher unsaturation in non-irrigated samples. Our results indicate that drought stress likely affects lipid profile composition, which could be driving higher herbivorous pest densities in drought-stressed crops.

In a screen for mutations that alter cell morphology and adhesion as a marker for cell wall composition alterations, an Arabidopsis seedling with root hairs that fail to elongate was identified. Root hairs are rounded and bubble-like, and the mutation was named Bubbles or bbl1. No other visible whole plant phenotypes were observed. Using backcrosses with wild type, and genomic sequencing of pooled F2 individuals with the Bubbles phenotype, 14 candidates for the mutant allele were identified. T-DNA alleles of one of these candidates showed a similar but partial phenotype to bbl1, and indicate that bbl1 is an allele of AT2G39110 previously identified as PBL38 (AvrPphB SUSCEPTIBLE1-LIKE38), a member of receptor kinase subfamily VII. PBL38 has been associated with the response to pathogens. bbl1 is a point mutation that causes a Glutamic acid to Lysine change at position 140, and is complimented by a C-terminal GFP fusion to the coding region of AT2G39110, indicating that the BBL1 gene (PBL38) is involved in correct root hair formation. AT2G39110 is expressed only in roots early in seedling maturation, and the GFP fusion protein localizes to the cell surface, consistent with the prediction that the gene encodes a receptor-like protein kinase. In bbl1 root hairs, the actin cytoskeleton does not form, while in bbl1 roots and other tissues normal actin cytoskeleton is observed.

Improving nitrogen use efficiency in rice would provide economic and environmental benefits, but little is known about root morphological and anatomical responses to low nitrogen. In this study, two sets of rice genotypes, one set from the RDP1 panel, and one set of recombinant inbred lines, were used to characterize responses to gradual nitrogen depletion by plant uptake and movement of nitrogen to deeper soil strata as a result of leaching, so that more nitrogen was available at depth in aerobic soil mesocosms in a greenhouse. There was significant genetic variation in shoot biomass reductions in response to low nitrogen. The root to shoot biomass ratio was increased by low nitrogen in both sets of genotypes. Relative investment in nodal root number was accentuated with low nitrogen, and shoot biomass was correlated with numbers and lengths of nodal and large lateral roots. There was genetic variation for nodal root number and length in both sets of genotypes. Anatomical responses to low nitrogen were assessed in nodal roots of the RILs, where root cross-sectional area, stele area, and metaxylem vessel number were reduced by low nitrogen, and root diameter was reduced in the RDP1 genotypes. There were significant interactions of nitrogen with genotype for stele area and percent aerenchyma in the RILs. Genetic variation for low nitrogen responses may be useful for selection of rice lines with greater nitrogen acquisition under nitrogen-leaching conditions.

Cannabis is well known for its pungent, skunk-like aroma. Recent chemical studies have identified prenylated and C6 volatile sulfur compounds as contributors to its skunky and citrus-like aromas, but the pathways that produce these compounds remain unknown. This gap limits efforts to explain variation in sulfur-aroma traits and to selectively enhance or reduce those traits. To address this gap, we used the known chemistry of sulfur-containing volatiles in Cannabis and characterized sulfur and volatile biosynthetic pathways in other plant species to select candidate enzyme groups. Because the GMO cultivar is anecdotally associated with a pronounced sulfurous aroma, reference protein sequences and profile hidden Markov models were used to search its version 1 (v1) primary high-confidence protein set of 55,790 sequences. These searches recovered 975 unique proteins. Sequence screening retained 941 candidates across 20 reporting categories; 939 contained all expected domains, while the two candidates assigned to the methionine gamma-lyase (MGL)-nearest category had no category-specific expected-domain rule. The largest reporting category comprised 359 proteins containing a cytochrome P450 domain, recovered through a search motivated by cytochrome P450 family 74 (CYP74) enzymes involved in oxylipin and plant volatile formation. Thirteen of these proteins were also recovered by at least one full-length CYP74 reference search. Other large reporting categories included 218 sugar-transferase, 83 glutathione-transferase, and 61 alcohol dehydrogenase candidates. Comparison with the Cannabis Expression Atlas linked 168 candidates to 128 annotated genes through 100%-identity amino-acid matches spanning at least 80% of each GMO v1 candidate protein. Twenty-nine genes were tissue-specific, including 13 root-specific and 6 trichome-specific genes. These results define candidates for biochemical testing and direct searches for additional enzymes acting upstream and downstream in Cannabis sulfur-volatile pathways.

Auxin is a hormone that is required for hypocotyl elongation during seedling development. In response to auxin rapid changes in transcript and protein abundance occur in hypocotyls and some auxin responsive gene expression is linked to hypocotyl growth. To functionally validate proteomic studies, a reverse genetics screen was performed on mutants in auxin-regulated proteins to identify novel regulators of plant growth. This uncovered a long hypocotyl mutant, which we called slim shady, in an annotated insertion line in IMMUNOREGULATORY RNA-BINDING PROTEIN (IRR). Overexpression of the IRR gene failed to rescue the slim shady phenotype and characterization of a second T-DNA allele of IRR found that it had a wild-type hypocotyl length. The slim shady mutant has an elevated expression of numerous genes associated with the brassinosteroid-auxin-phytochrome (BAP) regulatory module compared to wild-type, including transcription factors that regulate brassinosteroid, auxin and phytochrome pathways. Additionally, slim shady seedlings fail to exhibit a strong transcriptional response to auxin. Using whole genome sequence and transcriptomics data for SALK_015201C we determined that a novel single nucleotide polymorphism in PHYTOCHROME B was responsible for the slim shady phenotype. This is predicted to convert induce a frameshift and premature stop codon at leucine 1125, within the histidine kinase-related domain of the carboxy terminus of PHYB, which is required for phytochrome signaling and function. Genetic complementation analyses with phyb-9 confirmed that slim shady is a mutant allele of PHYB. This study advances our understanding of the molecular mechanisms in seedling development, by furthering our understanding of how light signaling is linked to auxin dependent cell elongation. Furthermore, this study highlights the importance of confirming the genetic identity of research material before attributing phenotypes to known mutations sourced from T-DNA stocks.

Research ConductedTo elucidate the functions of glycosylceramides, we generated and characterized mutants deficient in multiple steps contributing to their assembly in the model moss Physcomitrium patens. We mutagenized SPHINGOLIPID {Delta}8-DESATURASE, whose products are preferentially incorporated into glycosylceramides, and a suite of higher-order mutants combining sphingolipid {Delta}4-desaturase and glycosyl ceramide synthase. MethodsWe used targeted lipidomics to describe the chemotypes of all mutants. We used quantitative phenotype analysis, transcriptomics, and phytohormone profiling to understand the effects of these chemotypes on development and physiology. Key ResultsThese mutants present a range of phenotypes that collectively indicate that in P. patens (1) glycosylceramide deficiency impairs development, largely due to imbalance in free ceramide homeostasis (2) the synthesis of glycosylceramides is dependent upon the presence of a specific free ceramide profile (3) the {Delta}4-, but not the {Delta}8-desaturation, is strictly required for glycosylceramide synthesis, (4) cell division and differentiation, but not cell expansion, are affected by sphingolipid imbalance, and (5) sphingolipid imbalance results in oxylipin accumulation. ConclusionCollectively, our results elucidate the assembly and functions of glycosylceramides in a model bryophyte, and highlight conserved and specialized aspects of sphingolipid metabolism among plants.

Expansins are vital proteins that facilitate cell wall loosening, playing a crucial role in plant growth and development. This study investigates the structural and functional characteristics of the alpha-expansin precursor (GenBank ID: AAL79710.1) in Oryza sativa (Japanese rice). Through bioinformatics analyses, including ProtParam, CELLO, and conserved domain identification, we identified key biochemical properties, such as a molecular weight of approximately 28 kDa, a basic isoelectric point (pI 9.40), and significant levels of alanine and glycine. The CELLO analysis predicted the proteins localization primarily in the extracellular space, consistent with its role in modifying the cell wall. Homology searches revealed high similarity to expansin-A29 proteins in related species, while phylogenetic analysis indicated a close evolutionary relationship among monocots. Structural modeling predicted a well-folded protein, though refinement is necessary to address certain discrepancies highlighted in the QMEANDisCo analysis. Our findings underscore the evolutionary conservation of alpha-expansins and their integral role in plant physiology, particularly in cell wall dynamics and stress responses. This research enhances our understanding of alpha-expansins in rice and lays the groundwork for future studies aimed at manipulating these proteins to improve crop resilience and yield under changing environmental conditions.

Filamentous structures were observed in purified extracts from chrysanthemum, gerbera, sunflower and zinnia. When purified filament proteins were subjected to SDS-PAGE, the major protein associated with filaments from all three species has an apparent molecular mass of {approx}25 kDa. Protein bands from chrysanthemum, gerbera, and zinnia were subjected to N-terminal protein sequencing while proteins from sunflower were sequenced by CID MS/MS. All of the sequences shared highest similarity to the kunitz trypsin inhibitor family. The sequencing results indicated that the proteins lacked the signal sequences. We tested the gerbera filament protein for glycosylation and found that it was a glycoprotein. Together these results indicate that the filaments are composed of mature KTI protein. This is the first report of a KTI assembling into filaments and the first report of a filament forming Asteraceae enzyme.

Plants make diverse metabolites to outcompete neighboring organisms for space and resources. Some of these toxic metabolites broadly disrupt conserved molecular mechanisms, such as protein biosynthesis. Nonproteogenic amino acids (NPAAs) are a structurally diverse class of metabolites that interfere with protein biosynthesis. The proline (Pro) analog azetidine-2-carboxylic acid (Aze) inhibits plant growth through misincorporation during protein biosynthesis. However, it is unknown if a cascade of downstream stress responses is triggered following Aze misincorporation. Here, we investigate the morphological and stress responses in Arabidopsis grown on Aze. Investigation of root morphological responses show not only reduced root growth, but increased root branching following growth on Aze. Altered root morphology is coupled with a reduced gravitropic response. Aboveground organs were also affected by Aze, including reduced chlorophyll content, reduced photosynthetic efficiency, and increased anthocyanin content. We then tested whether Aze induces reactive oxygen species (ROS) accumulation using multiple approaches and observed both immediate and sustained accumulation of general ROS and H2O2 following treatment with Aze. When plants were grown on Aze supplemented with Pro, ROS levels were restored to normal levels, suggesting that reducing misincorporation events results in less downstream stress responses. In summary, we find that following Aze treatment a cascade of downstream stress responses is induced that exacerbates the effects of toxic NPAAs. This study sheds light on the mechanism of action of NPAAs and provides information on the downstream consequences of translational errors.

Screening a transposon-mutagenized soybean population led to the discovery of a recessively inherited chlorotic phenotype. This "vir1" phenotype results in smaller stature, weaker stems, and a smaller root system with smaller nodules. Genome sequencing identified 15 candidate genes with mutations likely to result in a loss of function. Amplicon sequencing of a segregating population was then used to narrow the list to a single candidate mutation, a single-base change in Glyma.07G102300 that disrupts splicing of the second intron. Single cell transcriptomic profiling indicates that this gene is expressed primarily in mesophyll cells and RNA sequencing data indicates it is upregulated in germinating seedlings by cold stress. Previous studies have shown that mutations to Os05g34040, the rice homolog of Glyma.07G102300, produced a chlorotic phenotype that was more pronounced in cool temperatures. Growing soybean vir1 mutants at lower temperatures also resulted in a more severe phenotype. In addition, transgenic expression of wild type Glyma.07G102300 in the knockout mutant of the Arabidopsis homolog At4930720 rescues the chlorotic phenotype, further supporting the hypothesis that the mutation in Glyma.07G102300 is causal of the vir1 phenotype.

A strategy to improve agricultural water productivity is to increase water use efficiency (WUE) at the level of plant transpiration through genetic selection. This requires detectable genetic variability in WUE and the ability to phenotype and select plants with higher WUE within a population. A proxy for phenotyping leaf level WUE by measuring carbon isotope signature ({delta}13Cleaf) has been supported by theory and data in C4 species. However, the functional relationship of {delta}13Cleaf and WUE in C4 species can be driven by genetics and environment. Therefore, a wide survey of existing natural variation is needed to quantify the heritability and identify various genetic factors that influence {delta}13Cleaf and WUE. In this study a genome-wide association panel was used to quantify the heritability of {delta}13Cleaf. We measured {delta}13Cleaf across a population of 360 genetically diverse lines of the C4 species Sorghum bicolor with single nucleotide polymorphic (SNP) markers determined from whole-genome resequencing. This analysis was conducted on two independent field environments where heritability of {delta}13Cleaf was evident and was driven by small genetic effects from loci that were consistently identified across environments. Candidate genes are presented that offer insights on future targets to manipulate and explore the functional relationship between {delta}13Cleaf and WUEi in C4 plants.

Sorghum is a crop that has become more relevant in recent years due to its uses and properties (biofuel, gluten-free flours) as well as its versatility to grow in unfavorable environmental conditions. Salinity is one of the main abiotic stresses affecting crop production and yield worldwide. The aim of this work was to study the response of sorghum seedlings to soil salinity in two genotypes with known performance to cope with water stress. Physiological parameters related to plant water status as well as the sodium content in the plant were analyzed. We studied the possible role of pricklet and microhairs in the response to salt conditions. Our results showed a differential response to salinity, probably denoting different mechanisms that involve internal water redistribution (in 200 mM NaCl) and a specific replacement of silicon by sodium (when the NaCl reaches 300 mM). The main result was that sodium was absent in all analyzed hairs and leaf surface. Surprisingly, we detected the presence of silicon inside the pricklet at 300 mM NaCl after 24 hours, but not in the microhair. NIPs aquaporins could be involucrate in silicon transport. Our novel results provide further evidence regarding the role of silicon in the response to salt stress. HighlightGrain sorghum has a different strategy to deal with salinity stress depending on the salt concentration, that involves the leaves pricklets and the migration of silicon.

I.Almond (Prunus dulcis [Mill.] D.A.Webb) exhibits an age-related disorder called non-infectious bud-failure (BF) affecting vegetative bud development and nut yield. The underlying cause of BF remains unknown but is hypothesized to be associated with heritable epigenetic mechanisms. To address this disorder and its epigenetic components, we utilized a monozygotic twin study model profiling genome-wide DNA methylation and gene expression in two sets of twin almonds discordant for BF-exhibition. Analysis of DNA methylation patterns show that BF-exhibition and methylation, namely hypomethylation, are not independent phenomena. Transcriptomic data generated from the twin pairs also shows genome-wide differential gene expression associated with BF-exhibition. After identifying differentially methylated regions (DMRs) in each twin pair, a comparison revealed 170 shared DMRs between the two twin pairs. These DMRs and the associated genetic components may play a role in BF-exhibition. A subset of 52 shared DMRs are in close proximity to genes involved in meristem maintenance, cell cycle regulation, and response to heat stress. Annotation of specific genes included involvement in processes like cell wall development, calcium ion signaling, and DNA methylation. Results of this work support the hypothesis that BF-exhibition is associated with hypomethylation in almond, and identified DMRs and differentially expressed genes can serve as potential biomarkers to assess BF-potential in almond germplasm. Our results contribute to an understanding of the contribution of epigenetic disorders in agricultural performance and biological fitness of perennials. II. SignificanceThis study examines epigenetic components underlying noninfectious bud failure, an aging-related disorder affecting almond. Results from this work contribute to our understanding of the implications of DNA methylation on agricultural production, namely perennial fruit and nut production, due to effects on growth, development, and reproduction. Describing the methylome of discordant, monozygotic twin almonds enables the study of genomic features underlying noninfectious bud failure in this economically important crop.

Radial expansion is a classic response of roots to mechanical impedance that has generally been assumed to aid penetration. We analysed the response of maize nodal roots to impedance to test the hypothesis that radial expansion is not related to the ability of roots to cross a compacted soil layer. Genotypes varied in their ability to cross the compacted layer, and those with a steeper approach to the compacted layer or less radial expansion in the compacted layer were more likely to cross the layer and achieve greater depth. Root radial expansion was due to cortical cell size expansion, while cortical cell file number remained constant. Genotypes and nodal root classes that exhibited radial expansion upon encountering the compacted soil layer also thickened in response to exogenous ethylene in hydroponic culture, i.e. radial expansion in response to ethylene was correlated with the thickening response to impedance in soil. We propose that ethylene insensitive roots, i.e. those that do not thicken and are able to overcome impedance, have a competitive advantage under mechanically impeded conditions as they can maintain their elongation rates. We suggest that prolonged exposure to ethylene could function as a stop signal for axial root growth.

Recent studies have demonstrated the presence of kynurenine (KYN) and kynurenic acid (KYNA) in several plant species, but the metabolic function of these metabolites remains undefined. We hypothesized that KYN and KYNA are metabolites of auxin and play a role in plant morphogenesis. To test our hypothesis, we developed a plant tissue-culture-based bioassay using Hypericum perforatum (St. Johns wort; SJW), a model system for auxin and indoleamine metabolism and pharmacological inhibitors (PF-04859989, RO-61-8048, and KMO inhibitor II, JM6) of human kynurenine pathways enzymes. SJW is an interesting model system because explants root in the absence of plant growth regulators but supplementation of the culture media with 10 M IAA induces a callus response without de novo root organogenesis. Supplementation of the culture media with 10 M KYN increased root number and internodal length relative to basal media. We used a previously validated high-resolution mass spectrometry analytical method to quantify KYN, KYNA, and 3-hydroxyanthranilic acid (3-HAA). KYN, KYNA and 3-HAA were quantified in roots and shoots of SJW grown on basal media. Supplementation of the culture media with 10 M KYN increased the concentration of KYN, KYNA and 3-HAA in roots and shoots. Treatment with 10 M IAA increased KYN and 3-HAA concentration in shoots. Three pharmaceutical candidates that are kynurenine pathway inhibitors in humans were taken up into the tissues from the culture media and increased KYN content as compared to basal control. Together, these data propose a role for KYN in IAA metabolism, shoot and root organogenesis. HighlightsO_LIKynurenine metabolites are detected and accumulate in H. perforatum tissue culture C_LIO_LIIAA redirects metabolism towards accumulation of KYN and 3-HAA in shoots C_LIO_LIExogenous KYN promotes KYNA accumulation C_LIO_LIPharmacological inhibition alters kynurenine pathway metabolite profiles in a tissue-specific manner C_LIO_LIKynurenine and IAA differentially regulate root development C_LI