Overexpression of AtSUT4 Induces Root Growth Inhibition by Rhizosphere Alkalization and Variation of Auxin Distribution in Arabidopsis thaliana

ABSTRACT As a member of the sucrose transporter (SUT) family, AtSUT4 occupies a distinct evolutionary category, implying unique functional specialization. However, studies on its involvement in growth and development regulation remain limited. Here, we demonstrated that AtSUT4 overexpression significantly inhibited root growth in Arabidopsis thaliana . Analyses using bromocresol purple indicators and non‐invasive micro‐test technology (NMT) revealed that AtSUT4 overexpression induced proton influx in the root apical meristem and elongation zones, while suppressing AHA1/AHA2 expression, ultimately resulting in an increased proton influx and extracellular alkalization of root tissues. Treatment with the H + ‐ATPase activator fusicoccin (FC) and the inhibitor N, N′‐dicyclohexylcarbodiimide (DCCD) indicated that AHA negatively regulated AtPIN2 expression. Consequently, overexpression of AtSUT4 down‐regulated AHA expression while promoting AtPIN2 expression and auxin accumulation in the root tips. Transcriptomic profiling further linked disrupted proton homeostasis and auxin accumulation to mark the down‐regulation of genes encoding ribosomal proteins, tubulins, and pectin degradation enzymes. These findings suggested that AtSUT4 ‐induced rhizosphere pH shifts and auxin perturbations concurrently impaired expansion forces (via cytoskeletal proteins) and enhanced limiting forces (via cell wall rigidity). Herein, we tentatively propose that AtSUT4 overexpression induced proton influx, which concurrently suppressed AHA1/2 expression and enhanced AtPIN2 transcription. This cascade culminated in rhizosphere alkalinization and variation of auxin distribution, collectively disrupting root cell growth. Our findings potentially established a previously unrecognized regulatory nexus between sugar signaling and auxin‐mediated developmental pathways in Arabidopsis thaliana .