Arabidopsis AZG2 Transports Cytokinins in vivo and Regulates Lateral Root Emergence

TOMÁS TESSI; SABINE BRUMM; EVA WINKLBAUER; BENJAMIN SCHUMACHER; GEORGINA PETTINARI; IGNACIO LESCANO; CLAUDIO GONZÁLEZ; DIERK WANKE; VERÓNICA MAURINO; KLAUS HARTER; MARCELO DESIMONE

NEW PHYTOLOGIST

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020

0028-646X

Cytokinin and auxin are key regulators of plant growth and development. During thelast decade transport mechanisms turned out to be the key for the control of local andlong-distance hormone distributions. In contrast to auxin, cytokinin transport is poorlyunderstood. Here, we show that Arabidopsis thaliana AZG2, a member of the AZG purinetransporter family, acts as cytokinin transporter involved in root system architecturedetermination. Even though purines are substrates for both AZG1 and AZG2, we founddistinct transport mechanisms. The expression of AZG2 is restricted to a small group of cells surrounding the lateralroot (LR) primordia and induced by auxins. Compared to wild-type, mutants carryingloss-of-function alleles of AZG2 have higher LR density, suggesting AZG2 as beingpart of a regulatory pathway in LR emergence. Moreover, azg2 is partially insensitiveto exogenous cytokinin, which is consistent with the observation that the cytokininreporter TCSnpro:GFP showed lower fluorescence signal in the roots of azg2 comparedto wild-type. These results indicate a defective cytokinin signalling pathway in the region of LRprimordia. The integration of AZG2 subcellular localization and cytokinin transportcapacity data allowed us to propose a local cytokinin:auxin signalling model for theregulation of LR emergence.