Kitaoka, N. | bioRxiv Science

bioRxiv2025

Two phytohormones synergistically induce parasitic weeds seed germination via KAI2d receptors

Root parasitic plants can severely decrease global crop production. The germination of their seeds is induced by host root-derived strigolactones (SLs). Considering this unique germination system, a "suicidal germination" method has been proposed to control root parasitic plants. However, this method requires the cost-effective production of germination inducers. In this study, we determined that jasmonates and SLs can synergistically induce the seed germination of root parasitic plants (Orobanche minor and Striga hermonthica). Biochemical analyses indicated that jasmonates and SLs cooperatively activate multiple divergent KARRIKIN INSENSITIVE 2 receptors. Our findings have elucidated the host recognition systems associated with these highly duplicated promiscuous receptors, with potential implications for developing a new strategy to protect crops against root parasitic plants.

plant biology↗

bioRxiv2025

(3R, 7S)-11-hydroxy-jasmonic acid is a major oxidative shunt product of jasmonate catabolism in Arabidopsis thaliana

Jasmonoyl-L-isoleucine (JA-Ile) is a pivotal oxylipin plant hormone that regulates numerous physiological processes and stress responses. Because JA-Ile is synthesized from jasmonic acid (JA), the cellular level of JA is tightly controlled. Although the oxidative catabolism of JA to 12-hydroxy-JA (12-OH-JA) is well-characterized, the biosynthesis, accumulation dynamics, and biological functions of 11-hydroxy-JA (11-OH-JA) remain poorly understood. Here, we conducted a comprehensive investigation of 11-OH-JA in Arabidopsis thaliana, encompassing its chemical synthesis, accumulation patterns, biological activity, and biosynthetic pathways. Using chemically synthesized 11-OH-JA of naturally occurring (3R,7S)-stereochemistry, we identified 11-OH-JA as the predominant hydroxylated JA derivative that accumulates following wounding. Enzymatic assays and in silico docking studies revealed that JOX1/2/3/4 exclusively catalyze the conversion of JA to 11-OH-JA, whereas 12-OH-JA is produced by distinct pathways. Notably, the quadruple mutant joxQ completely abolished 11-OH-JA accumulation without affecting 12-OH-JA levels. Furthermore, 11-OH-JA exhibited no binding affinity for the COI1-JAZ co-receptor, indicating that it acts as a biologically inactive shunt product of JA catabolism. Our findings establish JOX-mediated 11-hydroxylation of JA as a primary inactivation pathway, separate from 12-hydroxylation. Parallel, non-redundant inactivation routes deliver layered signal termination of costly defense signals. This study provides new insights into JA catabolism, highlighting 11-OH-JA as a crucial factor in the attenuation of jasmonate signaling, and thereby redefining the framework of JA turnover in A. thaliana.

plant biology↗