The pentose phosphate pathway influences maize radicle growth through regulating reactive oxygen species levels

Abstract

The radicle of maize (Zea mays L.) is the first nutritional organ to emerge during seedling growth. However, the regulatory mechanisms underlying the pentose phosphate pathway (PPP) in radicle growth remain poorly understood. In this study, we investigated the effects of PPP inhibition on maize radicle development by treating maize seeds with the PPP inhibitor (6-amino nicotinamide, 6-AN). We evaluated radicle phenotypes and key energy and redox indicators, and performed integrated transcriptomic and metabolomic analyses to identify differentially expressed genes, metabolites, and affected pathways. Our results showed that 6-AN treatment significantly reduced radicle length and altered the NADPH/NADP⁺ and NADH/NAD⁺ ratios, with a marked decrease in reactive oxygen species (ROS) levels, total antioxidant capacity (T-AOC), and activities of SnRK1 and NADPH oxidase (NOX). These findings suggest that PPP inhibition leads to a significant reduction in energy and redox status. Additionally, transcriptomic and metabolomic analyses revealed that redox-related pathways were significantly affected. Notably, ROS levels in the radicle were restored to some extent by the addition of H₂O₂ and NADPH, confirming that PPP regulates radicle growth by modulating ROS homeostasis through NADPH. This study highlights the critical role of the PPP in regulating radicle development via ROS balance.