Potassium transporter TRH1/KUP4 contributes to distinct auxin-mediated root system architecture responses.

Templalexis D, Tsitsekian D, Liu C, Daras G, Šimura J, Moschou P, Ljung K, Hatzopoulos P, Rigas S

Plant Physiol. - (-) - [2021-10-11; online 2021-10-11]

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 HAK/KUP/KT transporters that facilitate potassium 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 tiny root hairs 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 root hair defects. Applying a systems-level approach, the role of RAP2.11 and RSL5 transcription factors in root hair development was verified. Furthermore, ERF53 and WRKY51 transcription factors 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.

Swedish Metabolomics Centre (SMC) [Service]

PubMed 34633458

DOI 10.1093/plphys/kiab472

Crossref 10.1093/plphys/kiab472

pii: 6388045