HIGH AUXIN AND HIGH PHOSPHATE IMPACT ON RSL2 EXPRESSION AND ROS-HOMEOSTASIS LINKED TO ROOT HAIR GROWTH IN ARABIDOPSIS

SILVINA MANGANO, SILVINA PAOLA DENITA-JUAREZ, ELIANA MARZOL, CECILIA BORASSI, AND JOSÉ M. ESTEVEZ

Frontiers in Plant Science

Frontiers

Lugar: Lausanne; Año: 2018

1664-462X

Root hair size determines the surface area/volume ratio of the whole roots exposedto the nutrient and water pools, thereby likely impacting nutrient and wateruptake rates. Thespeed at which they grow is determined both by cell-intrinsic factors likehormones (e.g., auxin) and external environmental signals like nutrientavailability in the soil (e.g., phosphate). Overall root hair growth iscontrolled by the transcription factors RSL4 and RSL2. While high levels ofauxin promote root hair growth, high levels of inorganic phosphate (Pi) in themedia are able to strongly repress RSL4 and RSL2 expression linked to adecreased polar growth. In this work, we inquired the mechanism used by roothairs to integrate conflicting growth signals like the repressive signal ofhigh Pi levels and a concomitant high auxin exposure that promotes growth andquestioned whether these complex signals might activate known molecular playersin root hair polar growth. Under these conditions, RSL2 expression (but notRSL4) is activated linked to ROS production and root hair growth. On the otherhand, by blocking ROS production derived from the NADPH Oxidase C (or RBOHC forRESPIRATORY BURST OXIDASE HOMOLOG C) and ROS production from Secreted type-IIIPeroxidases (PERs), it was possible to repress the auxin growth-promotingeffect. This study identifies a new layer ofcomplexity between auxin, Pi nutrient availability and RSL2/RSL4 transcriptionfactors all acting on ROS homeostasis and growth at the root hair level.