. The monomeric GTPase ArfA1 participates in root hair polar growth and early responses to rhizobia

TRAUBENIK, SOLEDAD; RIVERO, CLAUDIO; SAVY, VIRGINIA; ZANETTI, MARÍA EUGENIA; BLANCO, FLAVIO; DALLA VIA, VIRGINIA

Congreso; XV Congreso Latinoamericano XXX Reunión Argentina de Fisiología Vegetal; 2014

Legume plants establish a mutualistic symbiosis with soil bacteria that convert N2 to forms that can be directly incorporated into the metabolism, accounting for almost half of the nitrogen incorporated into agricultural soils. Unravelling the molecular mechanisms involved in the establishment of the interaction is crucial to improve this biological process and alleviate the use of chemical fertilizers, preventing the environmental pollution associated to modern agricultural practices. Previously, we showed that ArfA1 is corregulated whit RabA2a, another GTPase involved in polar growth and early nodulation responses. ArfA1 is up-regulated in actively growing root hairs in response to rhizobia. In order to study the biological role of ArfA1 we generated GTP-locked (active) and GDP-locked (inactive) forms of ArfA1 by site-directed mutagenesis and expressed these constructs in composite plants of Medicago truncatula and Phaseolus vulgaris. Our results suggest that expression of both mutant forms of ArfA1 affects hairy root formation. The few roots formed in these composite plants exhibited shorter lateral roots and root hairs. The number and size of nodules was also affected in roots expressing the mutated forms of ArfA1. Our results support the proposed role of ArfA1 in polar growth processes and early nodulation responses.