IRON AND QUERCETIN INTERACTION ACTS AS A REGULATORY MECHANISM FOR SEED GERMINATION

Date

2025-12-19

Author

MANDEBERE, KUMBIRAI DEON

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Seed germination is a critical developmental process in the plant life cycle, controlled by a complex interplay of physiological, biochemical, and molecular processes that enable the seed to transition from a dry state through imbibition, testa rupture, and endosperm rupture. Iron (Fe) is an essential micronutrient that promotes plant growth and development, yet the specific mechanism by which it regulates seed germination remains poorly understood. We discovered that Fe accumulates in the chalaza of Arabidopsis thaliana seeds in a METAL TOLERANCE PROTEIN 8 (MTP8)-dependent manner and is mobilized during early germination. Externally applied Fe and Fe mobilizers revealed that testa germination speed positively correlates with Fe availability. Germination of two mutants, transparent testa7(tt7), lacking quercitrin, and peroxidase17 (prx17), lacking a type III apoplastic peroxidase expressed in the chalaza, was unresponsive to Fe. In vitro and in vivo assays showed that Fe forms a black complex with quercetin but not quercitrin. Fe supplementation blackened the chalaza of wild-type seeds, but not tt7, and this blackening intensified in the presence of a rhamnosidase enzyme, indicating Fe chelates quercetin derived from derhamnosylated quercitrin. Quercetin inhibited type III peroxidase activity in vitro, an effect reversed by Fe in a concentration-dependent manner. Consistently, PRX17-dependent peroxidase activity in imbibed seeds was induced by Fe and repressed by quercetin. Fe treatment promoted cuticle degradation and increased seed coat permeability. A reverse genetic screen identified MYB17 as a negative regulator of quercetin accumulation, as myb17 mutants showed enhanced blackening and elevated quercitrin levels. Collectively, these findings reveal that Fe, peroxidase activity, and quercetin form a regulatory mechanism controlling germination by modulating seed coat permeability.

Subject Keywords

Iron (Fe), Seed Germination, Endosperm, Peroxidase activity, Arabidopsis, quercetin

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https://hdl.handle.net/11511/118381

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Graduate School of Natural and Applied Sciences, Thesis