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
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
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