Koichi Yoneyama

• PhD
• Professor Emeritus at Utsunomiya University

Strigolactones (SLs) are butenolide-type plant hormones that play several roles in plants, such as suppressing shoot branching and promoting arbuscular mycorrhizal symbiosis. Recently, SLs have been reported to positively regulate disease resistance in plants. In this study, we analyzed the effect of the synthetic SL analog rac -4-bromodebranon ( r...

Plants have evolved elaborate mechanisms to detect neighboring plants, which typically involve the perception of “cues” inadvertently produced by the neighbor.¹ Strigolactones are hormonal signaling molecules²,³ that are also exuded into the rhizosphere by most flowering plant species to promote arbuscular mycorrhizal symbioses.⁴ Since flowering pl...

Strigolactones are low-molecular-weight phytohormones that play several roles in plants, such as regulation of shoot branching and interactions with arbuscular mycorrhizal fungi and parasitic weeds. Recently, strigolactones have been shown to be involved in plant responses to abiotic and biotic stress conditions. Herein, we analyzed the effects of...

Most plants interact with arbuscular mycorrhizal fungi, which enhance disease resistance in the host plant. Because the effects of resistance against bacterial pathogens are poorly understood, we investigated the effects of mycorrhizal colonization on virulent and avirulent pathogens using phytopathological and molecular biology techniques. Tomato...

The root parasitic weed broomrapes, Phelipanche spp., cause severe damage to agriculture all over the world. They have a special host-dependent lifecycle and their seeds can germinate only when they receive chemical signals released from host roots. Our previous study demonstrated that 2-phenylethyl isothiocyanate is an active germination stimulant...

Chickpea (Cicer arietinum L.) is a major pulse crop in Israel grown on about 3000 ha spread, from the Upper Galilee in the north to the North-Negev desert in the south. In the last few years, there has been a gradual increase in broomrape infestation in chickpea fields in all regions of Israel. Resistant chickpea cultivars would be simple and effec...

Root parasitic plants such as Striga, Orobanche, and Phelipanche spp. cause serious damage to crop production world‐wide. Deletion of the Low Germination Stimulant 1 (LGS1) gene gives a Striga‐resistance trait in sorghum (Sorghum bicolor). The LGS1 gene encodes a sulfotransferase‐like protein, but its function has not been elucidated. Since the pro...

Strigolactones (SLs) in the root exudates can be detected by germination assays with root parasitic weed seeds, but precise and accurate evaluation and quantification are possible only by chemical analysis with the liquid chromatography–tandem mass spectrometry (LC-MS/MS). Here we describe methods for root exudate collection, sample preparation, an...

Strigolactones (SLs) are a group of plant apocarotenoids that act as rhizosphere signaling molecules for both arbuscular mycorrhizal fungi and root parasitic plants. They also regulate plant architecture as phytohormones. The model legume Lotus japonicus (synonym of Lotus corniculatus) produces canonical 5-deoxystrigol (5DS) and non-canonical lotus...

Strigolactones (SLs) are essential host recognition signals for both root-parasitic plants and arbuscular mycorrhizal (AM) fungi in the rhizosphere, and in planta SLs or their metabolites function as a novel class of plant hormones that regulate various aspects of plant growth through crosstalk with other hormones. Although nutrient availability is...

Strigolactones (SLs) regulate important aspects of plant growth and stress responses. Many diverse types of SL occur in plants, but a complete picture of biosynthesis remains unclear. In Arabidopsis thaliana, we have demonstrated that MAX1, a cytochrome P450 monooxygenase, converts carlactone (CL) into carlactonoic acid (CLA) and that LBO, a 2‐oxog...

Strigolactones (SLs) are plant secondary metabolites derived from carotenoids. SLs play important roles in the regulation of plant growth and development in planta and coordinate interactions between plants and other organisms including root parasitic plants, and symbiotic and pathogenic microbes in the rhizosphere. In the 50 years since the discov...

Strigolactones (SLs) regulate important aspects of plant growth and stress responses. Many diverse types of SL occur in plants, but a complete picture of biosynthesis remains unclear. In Arabidopsis thaliana, we have demonstrated that MAX1, a cytochrome P450 monooxygenase, converts carlactone (CL) into carlactonoic acid (CLA), and that LBO, a 2-oxo...

Strigolactones (SLs) are a group of plant apocarotenoids that act as rhizosphere signaling molecules for both arbuscular mycorrhizal fungi and root parasitic plants. They also regulate plant architecture as phytohormones. The model legume Lotus japonicus produces canonical 5-deoxystrigol (5DS) and non-canonical lotuslactone (LL). The biosynthesis p...

Parasitic plants in the genus Striga, commonly known as witchweeds, cause major crop losses in sub-Saharan Africa and pose a threat to agriculture worldwide. An understanding of Striga parasite biology, which could lead to agricultural solutions, has been hampered by the lack of genome information. Here, we report the draft genome sequence of Strig...

Strigolactones (SLs) are carotenoid‐derived plant secondary metabolites that play important roles in various aspects of plant growth and development as plant hormones, and in rhizosphere communications with symbiotic microbes and also root parasitic weeds. Therefore, sophisticated regulation of the biosynthesis, perception and functions of SLs is e...

Root exudates from Lotus japonicus were found to contain at least three different hyphal branching-inducing compounds for the arbuscular mycorrhizal (AM) fungus Gigaspora margarita, one of which had been previously identified as (+)-5-deoxystrigol (5DS), a canonical strigolactone (SL). One of the two remaining unknown hyphal branching inducers was...

The response of plant root development to nutrient deficiencies is critical for crop production. Auxin, nitric oxide (NO), and strigolactones (SLs) are important regulators of root growth under low-nitrogen and -phosphate (LN and LP) conditions. Polar auxin transport in plants, which is mainly dependent on auxin efflux protein PINs, creates local a...

Strigolactones (SLs) can be classified into two structurally distinct groups: canonical and non-canonical SLs. Canonical SLs contain the ABCD ring system, and non-canonical SLs lack the A, B, or C ring but have the enol ether-D ring moiety which is essential for biological activities. The simplest non-canonical SL is the SL biosynthetic intermediat...

Strigolactones (SLs) can be classified into two structurally distinct groups: canonical and non-canonical SLs. Canonical SLs contain the ABCD ring system, and non-canonical SLs lack the A, B, or C ring but have the enol ether–D ring moiety which is essential for biological activities. The simplest non-canonical SL is the SL biosynthetic intermediat...

One of the germination stimulants for root parasitic weeds produced by maize (Zea mays) was isolated and named methyl zealactonoate (1). Its structure was determined to be methyl (2E,3E)-4-((RS)-3,3-dimethyl-2-(3-methylbut-2-en-2-yl)-5-oxotetrahydrofuran-2-yl)-2-((((R)-4-methyl-5-oxo-2,5-dihydrofran-2-yl)oxy)methylene)but-3-enoate using by 1D and 2...

Jasmonic acid (JA) is involved in a variety of physiological responses in seed plants. However, the detection and role of JA in lycophytes, a group of seedless vascular plants, have remained elusive until recently. This study provides the first evidence of 12-oxo-phytodienoic acid (OPDA), JA, and jasmonoyl-isoleucine (JA-Ile) in the model lycophyte...

In the present study, characterization of strigolactones (SLs) produced by some Tunisian faba bean genotypes partially resistant to Orobanche foetida Poir. and O. crenata Forsk. was conducted by LC–MS/MS and the results were compared with that of a susceptible genotype. Among the eight partially resistant genotypes grown hydroponically, only the ge...

A high-throughput screen in the model plant Arabidopsis unveils leads for potential agents to combat Striga, a devastating root parasitic weed that affects food crops in Sub-Saharan Africa.

The root holoparasitic angiosperm sunflower broomrape (Orobanche cumana) specifically affects sunflower (Helianthus annuus) growth and causes severe damage all over the world. This investigation was designed to examine the protective effects of salicylic acid (SA) treatment to the seeds of an O. cumana-susceptible cultivar of sunflower (TK0409). Su...

Root parasitic weeds (i.e. Phelipanche and Orobanche spp.) are a group of unwanted and highly damaging plants with a unique mechanism of action. They are completely dependent on attaching themselves to the host’s roots to consume photosynthates, nutrients and water. Seed germination is a key phase of their life cycle which is stimulated by secondar...

Significance Strigolactone hormones regulate many plant growth and developmental processes and are particularly important in regulating growth in response to nonoptimal conditions. Plants produce a range of bioactive strigolactone-like compounds, suggesting that the biosynthesis pathway is complex. Despite this complexity, only one type of enzyme,...

Strigolactones (SLs) are carotenoid-derived signaling molecules that mediate symbiotic and parasitic communications in the rhizosphere and plant hormones that regulate the growth and development of plants through crosstalk with other hormones. Natural SLs are classified into two groups based on the stereochemistry of the B–C ring junction. Rice and...

The response of the root system architecture to nutrient deficiencies is critical for sustainable agriculture. Nitric oxide (NO) is considered a key regulator of root growth, although the mechanisms remain unknown. Phenotypic, cellular, and genetic analyses were undertaken in rice to explore the role of NO in regulating root growth and strigolacton...

BACKGROUND Seed germination is a key phase of the parasitic plant life cycle which is stimulated by the secondary metabolites, mainly strigolactones (SLs), secreted by the host roots. Interventions during this stage would be particularly suitable for parasitic weed management practices since blocking these chemical signals would prevent seed germin...

Strigolactones (SLs) mainly produced in roots move upward to shoots and inhibit axillary bud outgrowth. However, SLs were not detected by LC-MS/MS in xylem saps collected from rice, tomato, cucumber, tobacco, sorghum, and Arabidopsis. d1-Orobanchol and d6-4-deoxyorobanchol that were fed to roots of rice plants were detected in shoots harvested 20 h...

Leafy gall syndrome is the consequence of modified plant development in response to a mixture of cytokinins secreted by the biotrophic actinomycete Rhodococcus fascians. The similarity of the induced symptoms with the phenotype of plant mutants defective in strigolactone biosynthesis and signalling prompted an evaluation of the involvement of strig...

Background and aims: Strigolactones (SLs) and their derivatives are plant hormones that have recently been identified as regulating root development. This study examines whether SLs play a role in mediating production of adventious roots (ARs) in rice (Oryza sativa), and also investigates possible interactions between SLs and auxin. Methods: Wil...

Root parasitic weeds in Orobanchaceae cause serious damage to worldwide agriculture. Germination of the parasites requires host-derived germination stimulants, such as strigolactones, as indicators of host roots within reach of the parasite's radicles. This unique germination process was focused on to identify metabolic pathways required for germin...

Strigolactones released from plant roots trigger both seed germination of parasitic weeds such as Striga spp. and hyphal branching of the symbionts arbuscular mycorrhizal (AM) fungi. Generally, strigolactone composition in exudates is quantitatively and qualitatively different among plants, which may be involved in susceptibility and host specifici...

Significance Strigolactones (SLs) are plant hormones that inhibit shoot branching and are parasitic and symbiotic signals toward root parasitic plants and arbuscular mycorrhizal fungi, respectively. Therefore, the manipulation of SL levels potentially improves the yield of crops. To achieve this goal, the biosynthesis pathway of SLs must be fully u...

Nitrogen and phosphorus fertilization in one side of split-root sorghum plants systemically reduced root contents of strigolactones in both sides of the split roots. Shoot-derived signals other than auxin appeared to be involved in this process. Strigolactones (SLs) are a novel class of plant hormones regulating both shoot and root architectures an...

Cucumber (Cucumis sativus) plants were found to exude at least 12 germination stimulants for root parasitic weeds including 5 known strigolactones, 7-oxoorobanchol, 7-oxoorobanchyl acetate, orobanchol, orobanchyl acetate, and 4-deoxyorobanchol. Two novel germination stimulants were purified from cucumber root exudates and their structures were dete...

Root exudates from the allelopathic plant, black oat (Avena strigosa Schreb.), were found to contain at least six different germination stimulants for root parasitic plants, but no known strigolactones (SLs). One of these germination stimulants was purified and named avenaol. Its HR-ESI-TOFMS analysis indicated that the molecular formula of avenaol...

Faba bean yield is severely constrained in Mediterranean region and Middle East by the parasitic weeds Orobanche crenata, O. foetida and Phelipanche aegyptiaca. Seed germination of these weeds is triggered upon recognition of host root exudates. Only recently faba bean accessions have been identified with resistance based in low induction of parasi...

Background In saffron (Crocus sativus), new corms develop at the base of every shoot developed from the maternal corm, a globular underground storage stem. Since the degree of bud sprouts influences the number and size of new corms, and strigolactones (SLs) suppress growth of pre-formed axillary bud, it was considered appropriate to investigate SL...

Esters of 3-nitrophloroglucinecarboxylic acid were found to be active photosystem II (PS II) inhibitors, as were the amides, indicating that, in their structures, the substituted phloroglucinol nuclei themselves plays a major roles in PS II inhibition. Among the phenylureidoalkyl esters tested, 3, 4-dichlorophenylurea compound having two amino hydr...

Studies on structure/activity relationships of phloroglucinol derivatives that had been designed based on the structures of grandinol and homograndinol potent photosystem II (PS II) inhibitors in Eucalyptus grandis, revealed that two electron-withdrawing groups which differ by their electron-withdrawing power on a phloroglucinol nucleus were essent...

Through the studies on structure-activity relationships of 5-acyl-3-(l-aminoalkylidene)-4-hydroxy-2 H-pyran-2,6(3 H)-dione derivatives in photosystem II (PS II) inhibition, overall lipophilicity of the molecule was found to be a major determinant for the activity. In the substituted N-benzyl derivatives, not only the lipophilicity but also the elec...

3-Acy1-5-(1-aminoalkylidene)-4-hydroxy-2 1 -aminoalkylidene)-4-hydroxy-2 H-pyran-2 H-pyran-2 derivatives carrying lipophilic amino groups were found to be highly potent inhibitors of photosynthetic electron transport, and both the acyl and the aminoalkylidene groups on the pyran ring appeared to be indispensable for high activity. The structural fe...

The seeds of Monochoria vaginalis require light to germinate. However, they are able to germinate in darkness in the presence of rice hulls. The mechanism of this phenomenon was investigated in this study, in which only the unsterilized seeds of Monochoria were induced to germinate by the presence of a rice hull extract. The rice hull extract was a...

Momilactones A and B in rice straw harvested at different growth stages were quantified by HPLC-MS-MS. They increased to their maximal levels at the heading stage and then gradually decreased. In addition, these phytotoxins were found to be relatively easily extracted with water.

Strigolactones (SLs) or their derivatives have recently been defined as novel phytohormones that regulate root development. However, it remains unclear whether SLs mediate root growth in response to phosphorus (P) and nitrogen (N) deficiency. In this study, the responses of root development in rice (Oryza sativa L.) to different levels of phosphate...

Germination is the first crucial step in the life cycle of obligate root parasitic Orobanchaceae, which cannot survive on their own. Therefore, germination of the tiny seeds with minimal reserves should occur only near host roots. These parasites detect the presence of hosts by using root-derived signalling molecules belonging to several distinct c...

Rice grassy stunt virus (RGSV) is a serious threat to rice production in Southeast Asia. RGSV is a member of the genus Tenuivirus, and it induces leaf yellowing, stunting, and excess tillering on rice plants. Here we examined gene responses of rice to RGSV infection to gain insight into the gene responses which might be associated with the disease...

Strigolactones (SLs) are essential host recognition signals for both root parasitic plants and arbuscular mycorrhizal fungi, and SLs or their metabolites function as a novel class of plant hormones regulating shoot and root architecture. Our previous study indicated that nitrogen (N) deficiency as well as phosphorus (P) deficiency in sorghum enhanc...

Strigolactones (SLs) are carotenoid-derived plant terpenes which function in the rhizosphere and in planta. In the rhizosphere, SLs induce seed germination in root parasitic plants and hyphal branching in arbuscular mycorrhizal (AM) fungi, therefore mediating both parasitic and symbiotic interactions with SL-producing plants and root parasitic plan...

Strigolactones (SLs) are plant secondary metabolites derived from carotenoids. SLs were originally isolated as germination stimulants for root parasitic plants witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.), and then found as host recognition signals for arbuscular mycorrhizal (AM) fungi with which >80% land plants form a...

(+)-Strigone was described earlier in a paper on isolation of strigol and then recently examined for hyphal branching activity in arbuscular mycorrhizal fungi as a strigolactone. Herein, it was isolated from root exudates of Houttuynia cordata, and its structure was confirmed by direct comparison with synthetic standards in LC-MS/MS, GC-MS, and (1)...

Major strigolactones (SLs) produced by rice (Oryza sativa L. cv. Nipponbare) and tobacco (Nicotiana tabacum L. cv. Michinoku No. 1) were purified and their stereochemical structures were determined by comparing with optically pure synthetic standards for their NMR and CD data and retention times and mass fragmentations in ESI-LC/MS and GC-MS. SLs p...

New roles for the recently identified group of plant hormones, the strigolactones, are currently under active investigation. One of their key roles is to regulate plant symbioses. These compounds act as a rhizosphere signal in arbuscular mycorrhizal symbioses and as a positive regulator of nodulation in legumes. The phosphorous and nitrogen status...

The aims of this study were to investigate the appearance of strigolactones in the green lineage and to determine the primitive function of these molecules. • We measured the strigolactone content of several isolated liverworts, mosses, charophyte and chlorophyte green algae using a sensitive biological assay and LC-MS ⁄ MS analyses. In parallel, s...

Strigolactones are a class of bioactive natural metabolites produced by plant roots and released into the rhizosphere. They were discovered as signals indispensable for the induction of germination of seeds of root parasitic weeds, but since then, interestingly, many other biological, physiological and ecological roles have been described. This has...

Phelipanche ramosa is a major parasitic weed of Brassica napus. The first step in a host-parasitic plant interaction is stimulation of parasite seed germination by compounds released from host roots. However, germination stimulants produced by B. napus have not been identified yet. In this study, we characterized the germination stimulants that acc...

Plants exude strigolactones (SLs) to attract symbiotic arbuscular mycorrhizal fungi in the rhizosphere. Previous studies have demonstrated that phosphorus (P) deficiency, but not nitrogen (N) deficiency, significantly promotes SL exudation in red clover, while in sorghum not only P deficiency but also N deficiency enhances SL exudation. There are d...

2,6-Diisopropylphenoxyacetic acid (DIPA) as well as gibberellins (GAs) was found to promote shoot growth and flowering in a perennial paddy weed Saggitaria pygmaea. In this paper, plant growth regulators, which have phytohonnonal activities including 2,4-D, S-abscisic acid (S-ABA), ethephon and benzyladenine (BA) or inhibitors of GA biosynthesis (p...

For the first time the strigolactone composition in root exudates of host plants of rare Orobanche spp. occurring in the spontaneous flora have been investigated by LC-MS/MS analysis. The obtained results were discussed in the context with host specificity of Orobanche spp. The results show host plant specific qualitative differences in the composi...

Nine-cis-epoxycarotenoid dioxygenase (NCED), belonging to the family of carotenoid-cleaving dioxygenases (CCDs), is the ratelimiting step in the abscisic acid (ABA) biosynthetic pathway in plants. Abamine is the first reported abscisic acid biosynthesis inhibitor to target NCED. Its utility has also been considered in the inhibition of other enzyme...

A number of studies have established that plant growth and development in oilseed rape (Brassica napus L.) are hampered by salinity stress. Nowadays, researchers have focused on the use of plant growth regulators to increase plant tolerance against salinity. An experiment was performed to evaluate the effects of 5-aminolevulinic acid (ALA, 30mgl−1)...

Strigolactones are apocarotenoids regulating shoot branching. They are also known to be exuded by plant roots at very low concentrations, stimulating hyphal branching of arbuscular mycorrhizal fungi and germination of root parasitic weed seeds. We show that strigolactones play a major role in host specificity of Orobanche and Phelipanche (the broom...

Strigolactones are a novel class of plant hormones controlling shoot branching in seed plants. They also signal host root proximity during symbiotic and parasitic interactions. To gain a better understanding of the origin of strigolactone functions, we characterised a moss mutant strongly affected in strigolactone biosynthesis following deletion of...

Strigolactones (SLs), originally characterized as germination stimulants for root parasitic weeds, are now recognized as hyphal branching factors for symbiotic arbuscular mycorrhizal fungi and as a novel class of plant hormones inhibiting shoot branching. In the present study, SLs in root exudates of 13 Asteraceae plants including crops, a weed, an...

The parasitic flowering plants of the genera Orobanche and Phelipanche (broomrape species) are obligatory chlorophyll-lacking root-parasitic weeds that infect dicotyledonous plants and cause heavy economic losses in a wide variety of plant species in warm-temperate and subtropical regions. One of the most effective strategies for broomrape control...

Eleven naturally occurring strigolactones (SLs) were examined for their germination-stimulating activity on the seeds of a root parasitic plant Orobanche minor Sm. Based on their activity, SLs are classified into 3 groups (A-C). Group A, the most active germination stimulant, consists of 3 monohydroxy-SLs, orobanchol, 2'-epiorobanchol, and sorgomol...

Among parasitic angiosperms, witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.) are the two most devastating root parasitic plants, causing enormous crop losses around the world. These root parasites have evolved special strategies to ensure their survival; the seeds germinate only when they are within the host rhizosphere so...

Salinity is one of the major constraints in oilseed rape (Brassica napus L.) production. One of the means to overcome this constraint is the use of plant growth regulators to induce plant tolerance. To study the plant response to salinity in combination with a growth regulator, 5-aminolevulinic acid (ALA), oilseed rape plants were grown hydroponica...

Witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.) are the two most devastating root parasitic plants belonging to the family Orobanchaceae and are causing enormous crop losses throughout the world. Seeds of these root parasites will not germinate unless they are exposed to chemical stimuli, ‘germination stimulants’ produced b...

Several triazole-containing chemicals have previously been shown to act as efficient inhibitors of cytochrome P450 monooxygenases. To discover a strigolactone biosynthesis inhibitor, we screened a chemical library of triazole derivatives to find chemicals that induce tiller bud outgrowth of rice seedlings. We discovered a triazole-type chemical, TI...

Strigolactones (SLs) were originally isolated from plant root exudates as germination stimulants for root parasitic plants of the family Orobanchaceae, including witchweeds (Striga spp.), broomrapes (Orobanche and Phelipanche spp.), and Alectra spp., and so were regarded as detrimental to the producing plants. Their role as indispensable chemical s...

The effects of seed coat removal and chilling on the germination of seeds of ten cultivars of ornamental peach (Prunus persica Batsch) were investigated. Seeds were rinsed in running tap water for 48 h in order to facilitate seed coat removal. Only a few non-chilled, intact seeds germinated (e.g., 6% of 'Hito' seeds). Seed coat removal and no chill...

Allelochemicals are the chemicals released from donor organisms into the environment and affect growth and development of receiver organisms. Allelochemicals involved in the plant–plant interactions can be classified according to their chemistries: alkaloids, terpenoids, phenolic compounds, benzoxazinoids, glucosinolates and isothiocyanates, and ot...

Strigolactones are considered a new group of plant hormones. Their role as modulators of plant growth and signalling molecules for plant interactions first became evident in Arabidopsis, pea, and rice mutants that were flawed in strigolactone production, release, or perception. The first evidence in tomato (Solanum lycopersicon) of strigolactone de...

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