Plants, Vol. 14, Pages 3246: Unveiling the GA4-Ferulic Acid Regulatory Axis: Redox-Mediated Suberization Governs Adventitious Rooting Recalcitrance in Pinus massoniana

Plants doi: 10.3390/plants14213246

Authors:
Yin Wang
Ruiling Yao

Pinus massoniana, a critically important afforestation species in subtropical China, shows severe adventitious rooting recalcitrance linked to endogenous gibberellin (GA) dysregulation. Our study reveals a GA4-mediated regulatory network that coordinates hormonal crosstalk, redox homeostasis, and cell wall remodeling. Treatment with the GA biosynthesis inhibitor paclobutrazol (PBZ, 100 mg·L−1) shortened rooting time by 32.5% and increased rooting success by 79.5%. We found that PBZ redirected GA flux by upregulating GA3-oxidase (GA3OX), leading to GA4 accumulation. However, elevated GA4 levels impaired root development by triggering suberization through ferulic acid (FA)-mediated redox imbalance. Application of GA4 (100 mg·L−1) reduced caffeoyl alcohol content by 54.4% but increased FA and caffeic acid levels 2.4–3.9-fold, shifting lignin precursors toward suberin biosynthesis. FA modulated H2O2 flux in a dose-dependent manner: 200 mg·L−1 optimized redox homeostasis (93.7% lower H2O2 influx), whereas 1000 mg·L−1 suppressed mitosis. The combination of PBZ (100 mg·L−1) and FA (200 mg·L−1) synergistically enhanced rooting success by 34.4% and achieved 95.8% field survival after two years (vs. 68.5% in controls), challenging the traditional view that lignification alone limits rooting in woody plants. This work provides the first evidence that the GA4-FA axis controls adventitious root formation in conifers via a Reactive oxygen species (ROS)-dependent switch between suberin and lignin metabolism, offering new strategies to overcome rooting barriers. The PBZ + FA protocol enables scalable clonal propagation of recalcitrant conifers, with potential applications in molecular breeding and forest restoration.

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Yin Wang www.mdpi.com