The transcription factor PdePHR1 increases phosphorus accumulation in poplar shoot and promotes root growth

Trees are major primary producers and long-term carbon sink by yielding a substantial amount of woody biomass, which relies on sufficient acquisition of mineral nutrient from soil by roots. Phosphate (Pi) is an essential, but often limited in soils, macronutrient. To sustain growth during Pi starvation, plants trigger an array of adaptive responses that are mainly controlled by the transcription factor of the PHOSPHATE RESPONSE 1 (PHR1) family. However, how the PHR1 functional homolog might influence the performance of forest trees remains unknown.

In this work, we identified PdePHR1from Populus deltoides x P. euramericana as a MYB-CC type transcription factor. Furthermore, overexpression of PdePHR1 in P. davidiana x P.bolleana triggers the expression of the Pi starvation response genes in replete Pi conditions, including genes mediating Pi uptake, remobilization, and signaling. Moreover, plants with overexpression of PdePHR1 exhibit enhanced Pi acquisition and translocation, leading to higher phosphorus accumulation in shoots under optimal conditions. Additionally, PdePHR1 overexpressing lines display substantially longer adventitious roots and more biomass accumulation independent of external Pi availability. Furthermore, overexpression of PdePHR1 sufficiently improves poplar performance under both Pi-replete and long-term depleted conditions.

Our data support that PdePHR1 acts as a central positive regulator of Pi starvation response and root growth. PdePHR1 overexpression is sufficient to enable not only increased phosphorus accumulation in shoot but also greatly enhanced root growth and overall woody biomass accumulation regardless of Pi availability. These findings provide a potential tool for increasing tree productivity and sustainable carbon sequestration under various environmental conditions.