A mechanistic framework for auxin dependent Arabidopsis root hair elongation to low external phosphate

Rahul Bhosale, Jitender Giri, Bipin K. Pandey, Ricardo F.H. Giehl , Anja Hartmann ,
Richard Traini , Jekaterina Truskina , Nicola Leftley , Meredith Hanlon , Kamal Swarup , Afaf Rashed , Ute Voß , Jose Alonso , Anna Stepanova , Jeonga Yun , Karin Ljung, Kathleen M. Brown, Jonathan P. Lynch, Liam Dolan , Teva Vernoux, Anthony Bishopp , Darren Wells, Nicolaus von Wirén, Malcolm J. Bennett & Ranjan Swarup

Phosphate (P) is an essential macronutrient for plant growth. Roots employ adaptive mechanisms to forage for P in soil. Root hair elongation is particularly important since P is immobile. Here we report that auxin plays a critical role promoting root hair growth in Arabidopsis in response to low external P. Mutants disrupting auxin synthesis (taa1) and transport (aux1) attenuate the low P root hair response. Conversely, targeting AUX1 expression in lateral root cap and epidermal cells rescues this low P response in aux1. Hence auxin transport from the root apex to differentiation zone promotes auxin-dependent hair response to low P. Low external P results in induction of root hair expressed auxin-inducible transcription factors ARF19, RSL2, and RSL4. Mutants lacking these genes disrupt the low P root hair response. We conclude auxin synthesis, transport and response pathway components play critical roles regulating this low P root adaptive response.