Plant Biotechnology最新文献

Plant-microbe interactions encompass a continuum from mutualism and commensalism to parasitism. Mutualists confer benefits such as nutrient acquisition or stress tolerance, whereas pathogens compromise host health, and commensals coexist without detectable harm or benefit. Importantly, these relationships are not fixed but are dynamic, shifting between interaction modes in response to host physiology, microbial adaptation, and environmental conditions. Such shifts can influence plant health, agricultural productivity, and ecosystem stability. This review synthesizes the mechanisms underlying these functional transitions and discusses how understanding the drivers of interaction shifts can inform sustainable agriculture and ecosystem management.

Sugars in root exudates play a pivotal role in shaping plant-microbe interactions in the rhizosphere, serving as carbon sources and signaling molecules that orchestrate microbial behavior, community structure, and plant resilience. Recent research has shed light on the dynamics of sugar levels in root exudates, the factors that influence their secretion, and the mechanisms by which these sugars drive microbial colonization and community assembly in the rhizosphere. Microbial communities, in turn, contribute to plant physiological changes that enhance growth and stress tolerance. While well-studied sugars such as glucose, sucrose, and fructose are known to promote chemotaxis, motility, and biofilm formation, emerging evidence suggests that less-studied sugars like arabinose and trehalose may also play significant roles in microbial interactions and stress resilience. Key challenges remain, including the accurate measurement of labile sugars that are rapidly metabolized by microbes, and the elucidation of genetic mechanisms underlying rhizosphere metabolic interactions in both host plants and microbes. Addressing these challenges will advance our understanding of sugar-mediated interactions and inform the development of sustainable agricultural innovations.

Pseudomonas protegens and related strains exert protective effects in plants by producing a wide range of secondary metabolites and extracellular enzymes that contribute to the suppression of plant pathogens in the rhizosphere. Our genomic and metabolomic studies on P. protegens demonstrated that intracellular low-molecular-weight effectors, such as guanosine tetraphosphate, fumarate, and γ-aminobutyrate, function as important signals in niche adaptation to plant roots. Extra- and intracellular levels of fumarate and succinate correlated with the regulation of secondary metabolism. We then investigated the involvement of exogenous amino acids in plant protection by P. protegens against Pythium damping off and root rot in cucumber. Among the amino acids tested, glutamate exerted positive effects on the efficacy of plant protection by P. protegens. The promoter activities of genes involved in the regulation of functions were characterized in detail, and we noted the dose-dependent regulation of functions in response to exogenous glutamate. In this mini-review, we introduce our previous findings on pseudomonads in terms of effective and ecological applications of this bacterium. The effective regulation of root-colonizing pseudomonads in the rhizosphere using extracellular signals that affect biocontrol activity will lead to advances in research on plant-microbe interactions.

The phyllosphere, referring to the leaf-dominated aerial parts of plants, represents a vast yet challenging habitat for plant-associated bacteria. A growing body of evidence indicates that phyllosphere bacteria provide host plants with a variety of beneficial effects, including growth promotion, enhanced stress tolerance, and pathogen resistance, garnering significant attention for their potential in biotechnological applications. However, our understanding of the molecular mechanisms underlying these bacterial functions in plant growth and health remains limited. Enhancing the beneficial effects of phyllosphere bacteria requires a deeper understanding of how they adapt to the harsh leaf environment, characterized by limited and unstable water and nutrient availability as well as host-induced defense responses. Moreover, recent studies are beginning to unravel the complex interplay among host plants and members of leaf bacterial communities, which serves as a key driver of the emergence of bacterial functions in the phyllosphere. In this review, we synthesize both early and recent advancements in our understanding of bacterial functions and adaptations in the phyllosphere at the levels of individual strains and communities and propose future research directions to harness phyllosphere bacteria for plant biotechnological applications.

The phyllosphere is a major microbial habitat, where resident communities promote plant growth, suppress pathogens, and induce disease resistance. Here we examined how rice growth stages influence microbial colonization by analyzing bacterial communities in the phyllospheres of three growth stages (panicle initiation, heading, harvesting) across three genotypes: 'Koshihikari' and two introgression lines. Bacterial communities were similar among genotypes in both leaves and stems at heading but became distinct at harvesting, indicating that growth stages and plant organ play primary roles in shaping community structure. Full-length 16S rRNA gene amplicon sequencing further revealed significant shifts in species composition, with Pseudomonas species, such as Pseudomonas brenneri and Pseudomonas helmanticensis, were consistently present across organs and stages, while Enterobacter species showed stage-specific colonization. These findings highlight the dynamic nature of phyllosphere microbial communities throughout plant development and underscore the importance of organ- and stage-specific factors in shaping plant-microbe interactions.

Wheat (Triticum aestivum L.) consists of three genomes, and notable mutant phenotypes can be observed when all homoeologs are knocked out due to functional redundancy among the homoeologous gene copies. Therefore, high editing efficiency is required to rapidly obtain loss-of-function mutants in wheat. The endogenous tRNA processing system of CRISPR/Cas9 genome editing enables the expression of multiple single-guide RNA (sgRNAs) under the control of a single promoter, facilitating simultaneous multiple genome editing in an organism. Here, we evaluated the genome editing efficiency of multiple sgRNA expressions with the tRNA processing system. At first, using sgRNA of quantitative trait locus for seed dormancy 1, polycistronic tRNA-sgRNA vectors were introduced into immature embryos, and genome editing efficiency was evaluated in the transformed T₁ plants. In the use of three sgRNA modules, there was no difference in the efficiency of genome editing among the positions of the sgRNAs. We subsequently tested simultaneous genome editing of multiple homoeologous loci. Simultaneous expression of six sgRNAs per gene to target all homoeologous loci increased the editing efficiency of all homoeologous loci up to 100%. Our study indicates that the tRNA processing system is highly effective at simultaneous genome editing of homoeologous loci of wheat.

For ornamental plants, inflorescence architecture is one of the most important traits to determine their commercial values. However, molecular mechanisms of inflorescence architecture determination have not yet been fully elucidated. LEAFY (LFY), which encodes a plant-specific transcriptional factor, has been shown to play a key role in the switch from vegetative to reproductive phases. Recent studies have demonstrated that LFY is involved not only in floral meristem induction but also in inflorescence architecture determination. Tricyrtis spp., which belong to the family Liliaceae, show two different types of inflorescence architecture: T. hirta produces both apical and lateral flowers, whereas T. formosana produces only apical flowers. In the present study, we isolated LFY-homologous genes from T. hirta and T. formosana (designated as ThirLFY and TforLFY, respectively) and analyze their functions and expression patterns as a first step toward elucidation of molecular mechanisms of inflorescence architecture determination in Tricyrtis spp. Alignment analysis based on amino acid sequences showed that both ThirLFY and TforLFY have functional motifs of LFY, and only three amino acid differences are found between them. Transgenic Arabidopsis thaliana plants overexpressing ThirLFY or TforLFY showed early flowering and production of secondary inflorescences, and no functional differences were observed between ThirLFY and TforLFY. In situ hybridization analysis showed that ThirLFY was expressed in both apical and lateral buds of T. hirta, whereas TforLFY was only expressed in apical buds of T. formosana. Thus, two different types of inflorescence architecture in Tricyrtis spp. may be caused by different expression patterns of LFY-homologous genes.

Histochemical detection of suberin lamellae has remarkably advanced our understanding of the roles of the apoplastic diffusion barrier in the root endodermis and the oxygen diffusion barrier in the root exodermis. Fluorol yellow 088 detects the aliphatic component of suberin and is one of the most reliable stains for detecting suberin lamellae in the endodermis and exodermis. Although fluorol yellow 088 staining can detect suberin lamellae in various plant roots by a simple procedure, conventional methods are time-consuming, as they need a long time to prepare the solution, stain, and wash the samples. Here, we propose a rapid method to minimize the time required to achieve suberin staining using root cross-sections. While conventional methods use polyethylene glycol-glycerol or lactic acid as the solvent, we found that fluorol yellow 088 readily dissolves into ethanol. This modification remarkably shortened the time required to prepare the solution, stain, and wash root cross-sections. Thus, our method will enhance the study of root anatomy and the histological development of plant roots.

Uncaria plants, belonging to the Rubiaceae family, develop characteristic hooks at their leaf axils. In the Japanese Pharmacopoeia, the hooks from three Uncaria species, including U. rhynchophylla, are collectively defined as "Uncaria Hook" and are widely used as medicinal materials. The pharmacological properties of the diverse bioactive metabolites in U. rhynchophylla, particularly monoterpenoid indole alkaloids (MIAs), have been extensively studied. In this study, we aimed to establish sterile cultures of U. rhynchophylla as models for investigating MIA biosynthesis. LC-MS/MS-based untargeted metabolomic analysis revealed that the metabolomic profiles of stems from cultured plants showed strong similarity to those of medicinal parts from mature plants, specifically the hooks and stems. Furthermore, the analysis indicated that the contents of oxindole and indole alkaloids exhibited distinct variations depending on the plant part and developmental stage, both in sterile plant cultures and mature plants. Our findings demonstrate that U. rhynchophylla can be maintained under sterile conditions while stably producing MIAs. These cultured plants can serve as a model system not only for studying MIA biosynthetic pathways but also for ensuring quality control of Uncaria Hook in medicinal applications. This model system would contribute to the fundamental research by enhancing our understanding of the biosynthetic mechanisms and facilitating applications such as metabolic control of the contents of bioactive compounds in Uncaria Hook.

Paeonia lactiflora, the roots of which are used as a crude drug, is one of the most widely used and important medicinal plants. The long cultivation period and low proliferation rate of P. lactiflora makes it difficult to propagate large numbers of plants within a short period. We developed a bio-nursery system using plant tissue culture techniques to contribute to the supply of P. lactiflora seeds and seedlings in Japan. Here, we report on the improved tissue culture and acclimation conditions for a more stable and efficient bio-nursery system. We investigated the effect of culture conditions on shoot proliferation and the effect of calcium concentration during root induction and acclimation of cultured plantlets. The results demonstrated that the number of shoots increased under the 15/5°C diurnal temperature changing treatment [15°C, 12 h light (fluorescent light, 80-130 µmol m^-2 s^-1)/5°C, 12 h dark] compared to a constant temperature of 15°C. A higher calcium concentration (6 mM Ca²⁺) during root induction resulted in more vigorous growth after transplantation to the soil. In addition, it was found that planting in a closed greenhouse at a constant temperature of 20°C after cold treatment was suitable for acclimation of cultured plantlets. These findings are expected to contribute to the future seedling supply of P. lactiflora.