Department of Biotechnology, Agricultural University of Athens, Athens 118 55, Greece.
Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala SE-756 61, Sweden.
Plant Physiol. 2022 Feb 4;188(2):1043-1060. doi: 10.1093/plphys/kiab472.
In plants, auxin transport and development are tightly coupled, just as hormone and growth responses are intimately linked in multicellular systems. Here we provide insights into uncoupling this tight control by specifically targeting the expression of TINY ROOT HAIR 1 (TRH1), a member of plant high-affinity potassium (K+)/K+ uptake/K+ transporter (HAK/KUP/KT) transporters that facilitate K+ uptake by co-transporting protons, in Arabidopsis root cell files. Use of this system pinpointed specific root developmental responses to acropetal versus basipetal auxin transport. Loss of TRH1 function shows TRHs and defective root gravitropism, associated with auxin imbalance in the root apex. Cell file-specific expression of TRH1 in the central cylinder rescued trh1 root agravitropism, whereas positional TRH1 expression in peripheral cell layers, including epidermis and cortex, restored trh1 defects. Applying a system-level approach, the role of RAP2.11 and ROOT HAIR DEFECTIVE-LIKE 5 transcription factors (TFs) in root hair development was verified. Furthermore, ERF53 and WRKY51 TFs were overrepresented upon restoration of root gravitropism supporting involvement in gravitropic control. Auxin has a central role in shaping root system architecture by regulating multiple developmental processes. We reveal that TRH1 jointly modulates intracellular ionic gradients and cell-to-cell polar auxin transport to drive root epidermal cell differentiation and gravitropic response. Our results indicate the developmental importance of HAK/KUP/KT proton-coupled K+ transporters.
在植物中，生长素的运输和发育紧密耦合，就像激素和生长反应在多细胞系统中密切相关一样。在这里，我们通过专门针对 TINY ROOT HAIR 1（TRH1）的表达来提供解开这种紧密控制的见解，TRH1 是植物高亲和力钾（K+）/K+摄取/K+转运体（HAK/KUP/KT）转运体的成员，通过共转运质子来促进 K+摄取。在拟南芥根细胞中。使用该系统可以精确定位到生长素向根尖的向顶运输与向基运输的特定根发育反应。TRH1 功能的丧失表明 TRHs 和根的向地性缺陷与根尖生长素失衡有关。在中央柱中特异性表达 TRH1 可挽救 trh1 根的负向地性，而在周围细胞层（包括表皮和皮层）中位置特异性表达 TRH1 则恢复了 trh1 缺陷。通过采用系统水平的方法，验证了 RAP2.11 和 ROOT HAIR DEFECTIVE-LIKE 5 转录因子（TF）在根毛发育中的作用。此外，在恢复根向地性时，ERF53 和 WRKY51 TF 过度表达，支持其参与向地性控制。生长素通过调节多个发育过程在塑造根系结构中起着核心作用。我们揭示了 TRH1 共同调节细胞内离子梯度和细胞间极性生长素运输，以驱动根表皮细胞分化和向地性反应。我们的结果表明 HAK/KUP/KT 质子偶联 K+转运体在发育中的重要性。
