Regulation of lateral root development by Azg2 mediated cytokinin transport.

TOMÁS TESSI; SABINE BRUMM; EVA WINKLAUER; IGNACIO LESCANO; CAROLINA MARTINI; VERÓNICA MAURINO; CHRISTOPHER GREFFEN; DIERK WANKE; KLAUS HARTER; MARCELO DESIMONE

Lecce

Congreso; XVII ENPER meeting; 2014

University of Salento

AZG (AZa-Guanin resistant) is a transporter protein family with two members in Arabidopsis thaliana (Cecchetto, 2004; Mansfield, 2009). Uptake experimentsrevealed that both transporters are able to transport purines and cytokinins (CKs) in planta with high affinity. Promoter studies using GFP as a reporter indicated that the expression of one family member, AZG2, is confined to few cells surrounding the lateral root primordia (LRP). Azg2 expression is induced by auxin in an ARF7 dependent manner. Moreover, first approaches to determine the subcellular localization revealed that Azg2 localizes at the plasma membrane. The highly specific expression pattern, in combination with the ability to transport CKs suggest that AZG2 could be involved in LR development regulation. To point out its relevance in LR development, Azg2 KO-lines (KOs) and overexpression lines (OEs) were analysed. Azg2 KOs showed higher LR densities than Wt plants. On the contrary, OEs presented lower LR densities than the Wt phenotype under specific nutritional conditions. Furthermore, when plants were treated with CKs, the differences between these phenotypes increased significantly. KOs lines showed a concentration dependent resistance towards CKs, while OE lines presented enhanced toxicity effects. All this data encourage us to propose Azg2 as a key factor in regulation of auxin / cytokinin cross-talk during lateral root development.