Disruption of LHT1 function alters ACC homeostasis and ethylene production leading to early senescence in Arabidopsis

Abstract

LHT1, a member of the lysine-histidine amino acid transporter family, has been implicated in a variety of plant physiological processes, yet its function in 1-aminocyclopropane-1-carboxylic acid (ACC) transport and overall plant development remains poorly understood. Here, we investigated the role of LHT1 in ACC uptake, homeostasis, and its physiological impacts in Arabidopsis. Using a heterologous system to study ACC transport and its selectivity, and a series of in planta assays across developmental stages, we characterized the ACC dose-dependent resistance in lht1–5 mutants, revealing that LHT1 plays a crucial role in ACC transport in both immature and adult plants. Additionally, we explored the involvement of LHT1 in senescence through grafting experiments and manipulation of ACC levels, confirming that disrupted ACC and ethylene dynamics govern the early senescence phenotype of lht1–5 mutants. Our findings suggest that LHT1 is essential not only for maintaining ACC homeostasis but also for modulating ethylene production and timing of senescence, paving the way for a deeper understanding of ACC transport in plant physiology.