Minisymposium 17: Mineral Nutrition

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Abs # M1704: The type I H⁺-PPase AVP1 functions at the intersection of auxin signaling and Pi sensing to mediate root architecture plasticity

Presenter:	Yang, Haibing       Contact Presenter
Authors	Yang, Haibing  (A)   Knapp, Jane  (A)   Murphy, Angus  (B)   Gaxiola, Roberto A (A)
Affiliations:	(A): University of Connecticut (B): Purdue University

Second only to nitrogen, phosphorous (P) is the most limiting macronutrient in agricultural production. Under limiting P conditions, carbon reallocation to roots results in increased growth, enhanced lateral root formation, increased numbers and lengths of root hairs, and a consequent increase in absorptive surface area. We have recently shown that manipulation of the type I H⁺-PPase AVP1 in both Arabidopsis and tomato results in a significant increase in root proliferation. Here we present data supporting a pivotal role for AVP1 in the regulation of auxin-dependent root architectural responses to low phosphate (P_i) in Arabidopsis and tomato plants. AVP1 abundance is regulated at both transcriptional and translational levels in plants treated with low P_i and/or exogenous auxin. Increases in plasmalemmal (PM) P-ATPase abundance induced by low P_i follow AVP1 induction. Overexpression of AVP1 in both Arabidopsis and tomato (AVP1OX) enhances plant performance under low P_i conditions, and AVP1OX root systems respond more vigorously to P_i limitation. Further, AVP1OX plants exhibit enhanced rhizosphere acidification and P_i uptake, but are not more sensitive than controls when challenged with aluminum phosphate (AlPO₄). AVP1OX tomato plants also produce significantly higher fruit yields than control plants when grown under low P_i. Finally, when AVP1 abundance is reduced by RNA interference, root proliferation is not enhanced in response to limiting P_i. Our data suggest that AVP1 functions at the intersection of auxin signaling and P_i sensing to mediate the plasticity of root architecture. We propose that a positive feedback loop enhances auxin-dependent root development under low P_i conditions: (1) low Pi enhances AVP1 expression. (2) Increased AVP1 abundance facilitates P-ATPase trafficking to the PM. (3) Increased P-ATPase at the PM results in apoplastic acidification and consequent increases in P_i uptake and auxin influx/polar efflux. (4) Intracellular auxin induces AVP1 and P-ATPase transcription. We conclude that AVP1 overexpression is an effective strategy to improve the performance of plants under limiting P_i conditions.