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Flax ( L.) is an economically important crop that is highly susceptible to f. sp. (Foln). While phytohormones are key regulators of defence, their interaction with polyamines during infection remains poorly understood. This study aimed to characterise hormonal dynamics in flax under Foln infection and the modulatory role of spermidine (Spd). Targeted UPLC-MS/MS profiling quantified over 30 hormone-related compounds, including auxins, cytokinins, gibberellins, jasmonates, salicylic acid, and abscisic acid, in shoots and roots of healthy, infected, and Spd-treated plants. Two Spd concentrations (10 and 100 mM) were applied under controlled in vitro conditions. Foln infection triggered tissue- and time-specific hormonal shifts, with early activation of jasmonate and auxin metabolism in shoots and later accumulation of salicylic acid and gibberellins in roots. Spd, particularly at 10 mM, reshaped these responses by reinforcing cytokinin and salicylic acid responses, stabilising auxin homeostasis, and enhancing jasmonate and abscisic acid responses. Spermidine coordinates hormone crosstalk, enabling balanced and efficient defence activation. The results highlight its potential as a priming agent enhancing flax resilience to .

The function of the plant hormone jasmonic acid (JA) in the development of tomato (Solanum lycopersicum) flowers was analyzed with a mutant defective in JA perception (jasmonate-insensitive1-1, jai1-1). In contrast with Arabidopsis (Arabidopsis thaliana) JA-insensitive plants, which are male sterile, the tomato jai1-1 mutant is female sterile, with major defects in female development. To identify putative JA-dependent regulatory components, we performed transcriptomics on ovules from flowers at three developmental stages from wild type and jai1-1 mutants. One of the strongly downregulated genes in jai1-1 encodes the MYB transcription factor SlMYB21. Its Arabidopsis ortholog plays a crucial role in JA-regulated stamen development. SlMYB21 was shown here to exhibit transcription factor activity in yeast, to interact with SlJAZ9 in yeast and in planta, and to complement Arabidopsis myb21-5. To analyze SlMYB21 function, we generated clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR associated protein 9 (Cas9) mutants and identified a mutant by Targeting Induced Local Lesions in Genomes (TILLING). These mutants showed female sterility, corroborating a function of MYB21 in tomato ovule development. Transcriptomics analysis of wild type, jai1-1, and myb21-2 carpels revealed processes that might be controlled by SlMYB21. The data suggest positive regulation of JA biosynthesis by SlMYB21, but negative regulation of auxin and gibberellins. The results demonstrate that SlMYB21 mediates at least partially the action of JA and might control the flower-to-fruit transition.

Cytokinins, which are central regulators of cell division and differentiation in plants, are adenine derivatives carrying an isopentenyl side chain that may be hydroxylated. Plants have two classes of isopentenyltransferases (IPTs) acting on the adenine moiety: ATP/ADP isopentenyltransferases (in Arabidopsis thaliana, AtIPT1, 3, 4-8) and tRNA IPTs (in Arabidopsis, AtIPT2 and 9). ATP/ADP IPTs are likely to be responsible for the bulk of cytokinin synthesis, whereas it is thought that cis-zeatin (cZ)-type cytokinins are produced possibly by degradation of cis-hydroxy isopentenyl tRNAs, which are formed by tRNA IPTs. However, these routes are largely hypothetical because of lack of in vivo evidence, because the critical experiment necessary to verify these routes, namely the production and analysis of mutants lacking AtIPTs, has not yet been described. We isolated null mutants for all members of the ATP/ADP IPT and tRNA IPT gene families in Arabidopsis. Notably, our work demonstrates that the atipt1 3 5 7 quadruple mutant possesses severely decreased levels of isopentenyladenine and trans-zeatin (tZ), and their corresponding ribosides, ribotides, and glucosides, and is retarded in its growth. In contrast, these mutants possessed increased levels of cZ-type cytokinins. The atipt2 9 double mutant, on the other hand, lacked isopentenyl- and cis-hydroxy isopentenyl-tRNA, and cZ-type cytokinins. These results indicate that whereas ATP/ADP IPTs are responsible for the bulk of isopentenyladenine- and tZ-type cytokinin synthesis, tRNA IPTs are required for cZ-type cytokinin production. This work clarifies the long-standing questions of the biosynthetic routes for isopentenyladenine-, tZ-, and cZ-type cytokinin production.

One of the most long-lived models in plant science is the belief that the long-distance transport and ratio of two plant hormones, auxin and cytokinin, at the site of action control major developmental events such as apical dominance. We have used in vivo deuterium labeling and mass spectrometry to investigate the dynamics of homeostatic cross talk between the two plant hormones. Interestingly, auxin mediates a very rapid negative control of the cytokinin pool by mainly suppressing the biosynthesis via the isopentenyladenosine-5′-monophosphate-independent pathway. In contrast, the effect of cytokinin overproduction on the entire auxin pool in the plant was slower, indicating that this most likely is mediated through altered development. In addition, we were able to confirm that the lateral root meristems are likely to be the main sites of isopentenyladenosine-5′-monophosphate-dependent cytokinin synthesis, and that the aerial tissue of the plant surprisingly also was a significant source of cytokinin biosynthesis. Our demonstration of shoot-localized synthesis, together with data demonstrating that auxin imposes a very rapid regulation of cytokinin biosynthesis, illustrates that the two hormones can interact also on the metabolic level in controlling plant development, and that the aerial part of the plant has the capacity to synthesize its own cytokinin independent of long-range transport from the root system.

Dinoflagellate inhabitants of the reef-building corals exchange nutrients and signals with host cells, which often benefit the growth of both partners. Phytohormones serve as central hubs for signal integration between symbiotic microbes and their hosts, allowing appropriate modulation of plant growth and defense in response to various stresses. However, the presence and function of phytohormones in photosynthetic dinoflagellates and their function in the holobionts remain elusive. We hypothesized that endosymbiotic dinoflagellates may produce and employ phytohormones for stress responses. Using the endosymbiont of reef corals Breviolum minutum as model, this study aims to exam whether the alga employ analogous signaling systems by an integrated multiomics approach. We show that key gibberellin (GA) biosynthetic genes are widely present in the genomes of the selected dinoflagellate algae. The non-13-hydroxylation pathway is the predominant route for GA biosynthesis and the multifunctional GA dioxygenase in B. minutum has distinct substrate preference from high plants. GA biosynthesis is modulated by the investigated bleaching-stimulating stresses at both transcriptional and metabolic levels and the exogenously applied GAs improve the thermal tolerance of the dinoflagellate. Our results demonstrate the innate ability of a selected Symbiodiniaceae to produce the important phytohormone and the active involvement of GAs in the coordination and the integration of the stress response.

The triterpenoid plant hormones brassinosteroids (BRs) are believed to influence almost every aspect of plant growth and development. We have developed a sensitive mass spectrometry-based method for the simultaneous profiling of twenty-two naturally occurring brassinosteroids including biosynthetic precursors and the majority of biologically active metabolites. Using ultra-high performance liquid chromatographic (UHPLC) analysis, the run time was reduced up to three times (to 9 min) in comparison to standard HPLC BRs analyses, the retention time stability was improved to 0.1–0.2 % RSD and the injection accuracy was increased to 1.1–4.9 % RSD. The procedures for extraction and for two-step purification based on solid-phase extraction (SPE) were optimised in combination with subsequent UHPLC analysis coupled to electrospray ionisation tandem mass spectrometry (ESI–MS/MS) using Brassica flowers and Arabidopsis plant tissue extracts. In multiple reaction monitoring (MRM) mode, the average detection limit for BRs analysed was close to 7 pg, and the linear range covered up to 3 orders of magnitude. The low detection limits for this broad range of BR metabolites enabled as little as 50 mg of plant tissue to be used for quantitative analyses. The results of determinations exploiting internal standards showed that this approach provides a high level of practicality, reproducibility and recovery. The method we have established will enable researchers to gain a better understanding of the dynamics of the biosynthesis and metabolism of brassinosteroids and their modes of action in plant growth and development.

As a result of the findings of scientists working on the biosynthesis and metabolism of steroids in the plant and animal kingdoms over the past five decades, it has become apparent that those compounds that naturally occur in animals can also be found as natural constituents of plants and vice versa, i.e., they have essentially the same fate in the majority of living organisms. This review summarizes the current state of knowledge on the occurrence of animal steroid hormones in the plant kingdom, particularly focusing on progesterone, testosterone, androstadienedione (boldione), androstenedione, and estrogens.

Gibberellins (GAs) and brassinosteroids (BRs) are important phytohormones that control plant development and responses to environmental cues by involving DELLA proteins and BRASSINAZOLE-RESISTANT1 (BZR1) respectively as key transcription factors. Here, we reveal a new role for JUNGBRUNNEN1 (JUB1) as a transcriptional regulator of GA/BR signalling in Arabidopsis thaliana . JUB1 directly represses the hormone biosynthesis genes GA3ox1 and DWARF4 ( DWF4 ), leading to reduced levels of GAs and BRs and typical GA/BR deficiency phenotypes exhibiting short hypocotyls, dwarfism, late flowering and male sterility. JUB1 also directly represses PHYTOCHROME INTERACTING FACTOR4 ( PIF4 ), a transcription factor connecting hormonal and environmental stimuli. On the other hand, JUB1 activates the DELLA genes GA INSENSITIVE ( GAI ) and RGA-LIKE 1 ( RGL1 ). In addition, BZR1 and PIF4 act as direct transcriptional repressors upstream of JUB1 , establishing a negative feedback loop. Thus, JUB1 forms the core of a robust regulatory module that triggers DELLA accumulation, thereby restricting cell elongation while concomitantly enhancing stress tolerance. Crosstalk in plant hormone signalling is important for growth and development. The Arabidopsis transcription factor JUB1 is at the core of a gibberellin/brassinosteroid transcriptional network that controls cell elongation and stress tolerance.

Cellular organisms use chemical signals for intercellular communication to coordinate their growth, development, and responses to environmental cues. The skeletons of majority of plant signaling molecules, mediators of plant intercellular ‘broadcasting’, are built from C₅ units of isoprene and therefore belong to a huge and diverse group of natural substances called isoprenoids (terpenoids). They fill many important roles in nature. This review summarizes current knowledge of the biosynthesis and biological importance of a group of isoprenoid-derived plant signaling compounds.

Many substances of secondary plant metabolism have often attracted the attention of scientists and the public because they have certain beneficial effects on human health, although the reason for their biosynthesis in the plant remains unclear. This is also the case for alkaloids. More than 200 years have passed since the discovery of the first alkaloid (morphine), and several thousand substances of this character have been isolated since then. Most often, alkaloid-rich plants are part of folk medicine with centuries-old traditions. What is particularly important to monitor for these herbal products is the spectrum and concentrations of the present active substances, which decide whether the product has a beneficial or toxic effect on human health. In this work, we present a fast, reliable, and robust method for the extraction, preconcentration, and determination of four selected alkaloids with an indole skeleton, i.e., harmine, harmaline, yohimbine, and ajmalicine, by ultra-high performance liquid chromatography coupled with tandem mass spectrometry. The applicability of the method was demonstrated for tobacco and Tribulus terrestris plant tissue, the seeds of Peganum harmala, and extract from the bark of the African tree Pausinystalia johimbe.