TaGSr-4D orchestrates lateral root development and tolerance to low nitrogen stress in Arabidopsis

Lateral roots are significant for capturing nutrients and water from the soil due to their capacity to expand the uptake area of the root system. Comprehending the molecular mechanisms that regulate lateral root development would be beneficial for optimizing the root system architecture (RSA) and improving crop yield. The enzyme GS (Glutamine synthetase) is a key enzyme that assimilates ammonium into glutamine. Previous study showed that TaGSr (Triticum aestivum L. ROOT GLUTAMINE SYNTHETASE) was mainly expressed in the root. However, little is known about the function of TaGSr in root system development in wheat. In this study, we showed that TaGSr-4D was expressed at all eight developmental stages of lateral root primordia and the heterologous expression of TaGSr-4D gene from wheat promoted the lateral root development in Arabidopsis. Overexpression of TaGSr-4D increased glutamine content and auxin content in root. Moreover, qRT-PCR analysis demonstrated that the expression of IAA14, LBD18, ARF6, ARF8, YUC3, YUC5, YUC6, and YUC9 were up-regulated in TaGSr-4D-OE Arabidopsis plants compared with wild-type. The absence of lateral roots in the arf7 arf19 mutant was not complemented by TaGSr-4D overexpression. These findings suggested that TaGSr-4D-regulated lateral root development is dependent on auxin signaling pathway. Furthermore, the shoot fresh weight of overexpression of TaGSr-4D OE-1 in Arabidopsis was greatly increased (39.29 %) compared with wild-type under low nitrogen conditions. This study may provides important clues for improving RSA and yield in wheat.