Jul 2026· Journal of Experimental Botany· 0 citations
Medicine
TL;DR
The current understanding of SL biosynthesis and transport in Arabidopsis thaliana and Oryza sativa is summarized and the physiological functions of different SL species as plant hormones and rhizosphere signaling molecules are discussed, which largely remain unresolved.
Abstract
Strigolactones (SLs) are a class of plant hormones that regulate diverse developmental processes and environmental responses. SLs also play important roles as allelochemicals in interactions with arbuscular mycorrhizal fungi (AMF) and root parasitic plants in the rhizosphere. Since their discovery as plant hormones nearly 20 years ago, SL biosynthesis, transport, and signaling have been extensively studied, primarily by characterizing mutants with increased shoot branching and by utilizing reverse genetic approaches in various plant species. Emerging evidence has revealed a series of new components of SL biology, expanding our knowledge of how a single plant species produces various types of SLs with diverse chemical structures and how SLs are released from roots into the soil. However, the bioactive forms of SLs that function as plant hormones and the mechanisms underlying their root-to-shoot transport have not yet been clearly elucidated. In this review, we summarize the current understanding of SL biosynthesis and transport in Arabidopsis thaliana and Oryza sativa. In addition, we discuss the physiological functions of different SL species as plant hormones and rhizosphere signaling molecules, which largely remain unresolved.
This study proposes a research and breeding roadmap progressing from molecular validation to medium- and short-term characterization in model trees and finally to multisite long-term ecological assessment, and presents a multiscale theoretical framework and testable pathways for translating SLs research from model plants to forestry applications.
Zhong-Zheng Ma, Wanxin Li, Qi Guo et al.· Physiologia Plantarum : An I...· 0 citations
Molecular insights of host–pathogen interactions offer decoding of sustainable strategies for developing resilient cultivars and effective management of false smut disease, highlighting stage-specific pathogenicity genes and rice defense mechanisms that control false smut disease development.
P. Parmar, B. Bashyal· Plant Molecular Biology· 0 citations
Karrikin (KAR) signaling plays crucial roles in plant development, regulating key traits such as photomorphogenesis, root hair development, and arbuscular mycorrhizal symbiosis. SUPPRESSOR OF MAX2 1 (SMAX1), a key negative regulator of the KAR pathway, has been functionally studied in several plant species. However, the SMAX1 protein remains poorly understood in Medicago truncatula, an important model legume, which limits the comprehensive understanding and application of the KAR pathway in legumes. In this study, we identified the single SMAX1 ortholog MtSMAX1 in M. truncatula. Sequence alignment and structural modeling analyses revealed that MtSMAX1 is highly conserved with SMAX1 homologs from other plant species. Yeast two-hybrid assays demonstrated that MtSMAX1 interacts with two KAR signaling receptors KARRIKIN INSENSITIVE 2 (MtKAI2a/b). In addition, both MtKAI2a/b interact with the F-box protein MORE AXILLARY GROWTH 2 (MtMAX2), suggesting a conserved KAR signaling pathway in M. truncatula. To further investigate the biological functions of MtSMAX1, we generated two distinct CRISPR-edited mutant lines. The loss-of-function mutant Mtsmax1, which carries a premature termination mutation, displays defective phenotypes including reduced seed size, dwarfism, and delayed flowering. In contrast, the Mtsmax1ΔQ210 mutant, harboring a single glutamine deletion at position 210, exhibits specific defects only in seed development. These phenotypic differences indicate a previously unreported role of MtSMAX1 in regulating legume seed development, with the conserved Q210 residue potentially involved in this process. Furthermore, MtSMAX1 overexpression lines exhibit phenotypes opposite to those of the mutants, further validating the biological functions of MtSMAX1. Gene expression analysis of key developmental marker genes revealed altered expression levels in MtSMAX1 mutants, which are tightly consistent with the corresponding phenotypic variations. These results suggest that MtSMAX1 likely functions as an important transcriptional regulator to modulate the expression of downstream developmental genes. Collectively, our findings establish MtSMAX1 as a pivotal regulator of multiple developmental processes in legumes and provide a foundation for elucidating the broader biological functions and regulatory mechanisms of the KAR signaling pathway.
Wanyuan Li, Hui Song, Miao Xie et al.· Plant physiology and biochem...· 0 citations
ABSTRACT Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with plant roots, profoundly shaping root system architecture (RSA) and influencing nutrient acquisition in crops. This modulation begins during the early pre‐symbiotic stage, when plants and fungi interact without physical contact. Root formation is orchestrated by signaling molecules, including hormones such as auxin (IAA) and strigolactones (SLs), as well as reactive nitrogen species such as nitric oxide (NO). However, the mechanisms by which AMF spores modulate these pathways to influence root development in rice remain largely unexplored. Here, we investigated the effects of Rhizophagus irregularis spores on root formation in Oryza sativa L., focusing on IAA, SLs, and NO modulation. Exposure to both live and autoclaved spores enhanced lateral root formation in adventitious roots, whereas only live spores promoted elongation and secondary branching of large lateral roots (LLRs), a rice‐specific feature. These effects were correlated with increased IAA levels, transcriptomic changes, and decreased SL accumulation, revealing an integrated signaling network controlling LLR development. Histochemical analyses revealed NO accumulation in the root elongation zone and apex, accompanied by the upregulation of the high‐affinity nitrate transporter OsNRT2.1 in LLRs. Together, our findings reveal a root‐type‐specific involvement of IAA, SLs, and NO in shaping RSA during the pre‐symbiotic stage of AMF interactions. This study provides new insights into early signaling events that mediate host discrimination and regulate root architecture during the pre‐symbiotic phase of AMF establishment.
Giulia Raffaele, Marilena Ronzan, E. Del Dottore et al.· Physiologia Plantarum : An I...· 0 citations
Thidiazuron (TDZ) is a synthetic growth regulator with cytokinin-like activity, widely used in biotechnology, but its physiological effects during the early stages of plant development are not yet fully understood. In this study, the impact of increasing concentrations of TDZ on the germination and early development of Arabidopsis thaliana was evaluated, with particular attention to physiological responses and their dose-dependent patterns. Seeds of the Col-0 ecotype were germinated in the presence of TDZ and analyzed using integrated approaches including morphological observations, photosynthetic efficiency measurements, and metabolic and hormonal profile analysis. The results show that low concentrations of TDZ do not significantly alter the main physiological parameters, while higher doses induce progressive alterations in cotyledon vascular pattern, hormonal imbalances, and a reduction in photosynthetic efficiency, indicating a functional impairment. Transcriptomic analysis revealed coordinated modulation of genes involved in hormonal regulation, energy metabolism, and stress responses, consistent with the observed phenotypes. Overall, the study demonstrates that TDZ exerts distinct and highly dose-dependent physiological effects, delineating a continuum ranging from responses compatible with normal development to those indicative of impaired development to conditions of physiological stress, and providing useful insights for a critical assessment of the benefits and risks associated with the use of this compound.
E. Campo, Federica de Marchi, Giulia Giovanna Salerno et al.· Plant physiology and biochem...· 0 citations
The discovery of the apocarotenoid growth regulator zaxinone has fundamentally expanded the current understanding of plant growth, development, and hormone signaling. Synthesized in rice by Zaxinone Synthase (ZAS), this metabolite functions as a regulator of plant physiology, metabolism and hormone homeostasis, thereby modulating plant growth, architecture and rhizosphere communication. Recent genetic, structural and biochemical analyses have revealed its impact on primary metabolism, interference with hormonal signaling and role in determining the level of key plant hormones, including strigolactones, cytokinins and abscisic acid. Exogenous application and genetic approaches, including OsZAS1 overexpression, have demonstrated that elevated endogenous zaxinone levels promote rice growth and productivity. These studies also unveiled the complex role of zaxinone in regulating the establishment and development of arbuscular mycorrhization. To overcome the limited accessibility of zaxinone, highly efficient mimics of zaxinone (MiZax) have been developed and evaluated for their bioactivity and utility for agricultural applications. MiZax have been shown to retain the key biological activities and physiological responses of zaxinone, including the promotion of crop growth and productivity, enhancement of fertilizer usage efficiency, suppression of root parasitic weed infestation, as well as transient effects on root-associated microbial communities. This Expert View provides insights into how the discovery of zaxinone expands our conceptual landscape of plant growth substances, lays the foundation for a new type of biostimulants, and identifies the critical open questions for guiding future research into apocarotenoid-mediated growth regulation.
Mohamed A. Salem, Juan C. Moreno, Sondos Abozahra et al.· Journal of Experimental Bota...· 0 citations
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