Jasmonic acid (JA) and its biologically active form jasmonoyl isoleucine (JA-Ile) regulate plant growth, development, and defense responses to disease and wounding stresses. First, we attempted to elucidate JA signaling in rice. We focused on a rice JA-responsive bHLH transcription factor RERJ1 and found that the expression of RERJ1 is tightly regulated by JA accumulation in rice leaves treated with wounding or drought stresses. We also identified JA-responsive cis-elements in the upstream region of OsChia4a, which encodes a rice chitinase, suggesting that a bHLH transcription factor regulates its inductive expression. In addition, we revealed that RERJ1 regulates defense response against insect herbivores. These results indicated the contribution of RERJ1 on rice JA signaling.

In contrast to vascular plants, not JA but 12-oxo-phytodienoic acid (OPDA) and its related compounds are bioactive in bryophytes. We found that OPDA and its related compounds have biological activity in momilactone-producing moss Calohypnum plumiforme. We also showed that OPDA signaling components are conserved in C. plumiforme, as in the other bryophytes. This review summarizes our studies regarding the signal transduction of JA and its related compounds in disease and wounding stress responses.

In the canonical strigolactone (SL) biosynthesis, the ring-closing reaction of carlactonoic acid (CLA) and subsequent modification of the A- and B-ring are thought to generate structurally diverse SLs. It was found that VuCYP722C and SlCYP722C in cowpea and tomato, respectively, are involved in the direct conversion of CLA to orobanchol without passing through 4-deoxyorobanchol. Knocking out this gene in tomato resulted in no detection of canonical SLs in root exudates, whereas the knockout plants did not show the branching phenotypes, suggesting that an active hormone that inhibits shoot branching is derived from non-canonical SLs. The study also revealed that GaCYP722C of cotton catalyzes the conversion of CLA to 5-deoxystrigol (5DS). Therefore, members of CYP722C subfamily, which is widely conserved in dicot plants, are key enzymes involved in the canonical SL biosynthesis. Additionally, the enzymes responsible for the structural diversification of canonical SLs in sorghum were investigated, and SbCYP728B35 was identified as sorgomol synthase that introduces a hydroxy group at C-9 of 5DS. These results indicate that cytochrome P450 is deeply involved in the canonical SL biosynthesis and reveal a part of the structural diversification mechanism in SL biosynthesis.

In plant science, small molecules with biological activities are widely used to elucidate and understand biological systems. For example, plant hormones are essential for normal plant growth, and regulating their functions leads to significant changes in plant phenotypes. Strigolactones (SLs) are carotenoid-derived small molecules that have a broad spectrum of functions, including plant hormone activities and chemical mediation of rhizosphere communication with root parasitic weeds and arbuscular mycorrhizal fungi. Therefore, chemicals that regulate the SL functions would be widely used in agriculture. For example, a variety of compounds with SL-like activity have been developed to reduce the seed banks of root parasitic weeds in the field. Other compounds with SL-like activity selectively suppress shoot branching while weakly or not stimulating germination of root parasitic weeds. Inhibitors of SL receptors, conversely, can induce increased shoot branching and dormancy of root parasitic weeds. Small molecules that bind to SL biosynthetic enzymes inhibit SL biosynthesis, thus mimicking mutations in SL biosynthesis and perception, leading to increased shoot branching and seed dormancy of root parasitic weeds. In recent years, some SL function regulators have been designed based on the reaction mechanisms of SL biosynthetic enzymes and SL perception. Here, we overview the SL function regulators reported to date and discuss their potential applications in agriculture.

Plants synthesize a huge array of metabolites that contribute to adaptation to various environments. Recently, it has been revealed that these plant specialized metabolites (PSMs) shape and modulate the rhizosphere microbiota, which play important roles in plant growth and fitness. This review summarizes the roles of PSMs in the interactions with microbiota analyzed by the methods of direct application of PSMs to soil and discusses perspectives in this research field.

Vascular system is essential for transporting water and nutrients throughout the plant body. During secondary growth, vascular stem cells located in the cambium undergo cell proliferation to give rise to xylem and phloem cells. For ensuring the permanent secondary growth, robust regulation of vascular stem cell maintenance is required. A peptide hormone tracheary element differentiation inhibitory factor (TDIF) and its receptor TDIF RECEPTOR (TDR) play central roles in controlling vascular stem cell maitenance. Further studies have uncovered the downstream cascade of the TDIF-TDR signaling. Based on these findings, Vascular cell Induction culture System Using Arabidopsis Leaves (VISUAL) was developed for molecular genetic studies of vascular cell differentiation. By utilizing VISUAL system, it is found that TDIF competes with a plant hormone brassinosteroid to regulate xylem cell differentiation by controlling their common downstream transcription factor BRI1-EMS-SUPPRESSOR (BES1). Moreover, molecular studies reveal the competitive relationship among BES family members in the regulation of vascular cell differentiation, suggesting the existence of signaling cross-talks at various signaling processes. Here I summarize the importance of cross-talk among various plant hormones including TDIF in the robust regulation of vascular stem cell maintenance.

Cyanobacteria perform oxygenic photosynthesis, and so have developed highly organized photoresponsive systems to acclimate to changing light environments. Among various photoreceptors, linear tetrapyrrole-binding cyanobacteriochrome photoreceptors play central roles for these systems. The cyanobacteriochrome photoreceptors are distant relative of the plant phytochromes showing red/far-red reversible photoconversion. In the case of the cyanobacteriochrome photoreceptors, the spectral properties are highly diversified to sense various light colors covering UV and visible light regions. In recent years, we have focused on quite unique cyanobacterium Acaryochloris marina which utilizes not chlorophyll a but chlorophyll d for reaction center pigment of photosystems. Because chlorophyll d absorbs longer wavelength far-red light than chlorophyll a, we assumed that A. marina might have photorecetors to sense longer wavelength far-red light. In fact, we could expectedly identify novel cyanobacteriochrome photoreceptors to sense far-red light by incorporating unique chromophores. In addition, we could serendipitously discover various novel photoreceptors with unique spectral properties. In this review, we will introduce details of these findings and applicative potentials of the discovered molecules for optogenetic control and fluorescence bioimaging.

ANAC071 and its homolog ANAC096 are plant-specific transcription factors required to initiate cell division during tissue reunion of incised flowering stems and hypocotyl grafting in Arabidopsis thaliana;their mechanisms remain unknown. This study showed that both ANAC071 and ANAC096 were expressed at these sites before the wound-induced cambium formation. We also found that the anac-multiple mutants significantly reduced wound-induced cambium formation in incised stems and reduced the conversion of mesophyll cells to cambium cells in an ectopic vascular cell induction culture system using Arabidopsis leaves (VISUAL). These results suggest that ANAC071 and ANAC096 are involved in the process of “cambialization,” the transformation of differentiated cells into cambium-like cells and that these cambium-like cells proliferate and repair wounded tissues during the process of tissue-reunion.

N-Allylglycine and choline chloride are known to promote photosynthesis of wheat protoplasts. To clarify whether N-allylglycine promotes plant growth, Arabidopsis thaliana was grown in a medium containing N-allylglycine. Dry weight of Arabidopsis thaliana was increased about 1.2-fold by treatment of N-allylglycine and choline chloride. N-Allylglycine also increased the dry weight of Brassica rapa by about 1.4 times. To examine the mechanism of growth promotion by N-allylglycine, Brassica rapa genes whose expression was altered by treatment with N-allylglycine and choline chloride were examined by RNAseq analysis. The transcriptome analysis revealed that treatment with N-allylglycine and choline chloride commonly up-regulated the expression of genes encoding proteins in the photosystem. These results suggest that the growth promotion by N-allylglycine and choline chloride may be due to the activation of photosystem II.

Anesthesia was firstly discovered in the 19th century and has been essential for many medical treatments such as surgery. Nevertheless, the action of anesthetics on nerve cells how the drugs induce the state of unconsciousness remains largely unclear. One of the big mysteries is that many anesthetic molecules share no or little similarities in atoms and structures. Even chemically-inert xenon gas is known to be an excellent anesthetic. It makes the study of anesthetics challenging to find out the target of the drug molecules in the biological systems. Besides animals, narcotic drugs have a broad effect on living organisms, including plants. French physiologist Claude Bernard performed the immobilization of the mimosa plant with diethyl ether anesthesia in the late 19th century. I reproduced the experiments of Bernard and tried to see what happens in living plant cells under anesthesia using current research techniques. Here I would like to introduce my results and discuss the possible action of anesthetics.

Agricultural production has suffered a lot of losses from herbivorous pests, as well as from viral infections that they transmit. Many of these pests have acquired resistance to insecticides, and there is an urgent need to break away from traditional chemical control. Jasmonic acid is a type of plant hormone and plays an important role in promoting the aging of plants, suppressing the growth of plants, the dormancy breaking, and in defensive responses to injuries and feeding of herbivorous insects. Therefore, it has been reported so far that some pests avoid some plants treated with jasmonic acid. Prohydrojasmon is a derivative of jasmonic acid, and an agrochemical registration as a pest repellent was obtained in March 2021 with the purpose of alleviating the harmful effects of thrips on tomatoes. Prohydrojasmon can be used continuously in agricultural production because of its low environmental impact and its low potential for development of resistance by insects.