Aux/IAA Transcription Factors Modulating Drought-Responsive Root System Remodeling in Potato

Aux/IAA proteins function as central transcriptional repressors in auxin signaling and have been implicated in coordinating developmental responses to environmental stress, particularly through modulation of root system architecture. However, the contribution of auxin signaling components to drought-associated root plasticity in improving drought resilience in potato (Solanum tuberosum L.) remains unclear. In this study, we profiled Aux/IAA responses to water deficit across underground tissues by RNA sequencing of root tips, stolon tips, and tubers from two cultivars (Qingshu 9 and Atlantic) with contrasting drought tolerance. Drought treatment induced broad transcriptional changes in the Aux/IAA family, with the majority of members showing increased expression in at least one tissue. qRT-PCR across tissues and developmental stages validated distinct spatiotemporal patterns for selected candidates. Among these, the StIAA3, StIAA6, StIAA22, and StIAA25 genes displayed drought-inducible expression, whereas StIAA24 showed an opposite trend. To probe functional relevance, we generated overexpression and knockdown lines for StIAA3, StIAA6, StIAA22, and StIAA24. Altered expression of these genes was consistently associated with measurable changes in root architecture traits, including root length, diameter, and volume, under water-deficit conditions. These findings reveal insights into the contribution of auxin signaling components to drought-associated root plasticity in potato. The identified drought-responsive Aux/IAA candidates that link root architectural remodeling provide a foundation for mechanistic dissection and underground tissue remodeling of architecture enhancement in root crops.