Comparative Phylogenetic and Expression Analysis of Small GTPases Families in Legume and Non-Legume Plants

FLORES, ANA CLAUDIA; VILLAGRA, ULISES MANCINI; FLORES, ANA CLAUDIA; VILLAGRA, ULISES MANCINI; SAVY, VIRGINIA; BLANCO, FLAVIO; SAVY, VIRGINIA; BLANCO, FLAVIO; VIA, VIRGINIA DALLA; ZANETTI, MARÍA EUGENIA; VIA, VIRGINIA DALLA; ZANETTI, MARÍA EUGENIA

Plant Signaling & Behavior

Taylor &Francis

Año: 2018 vol. 00 p. 1 - 12

1559-2316

Background: Small monomeric GTPases act as molecular switches in several processes that involve polarcell growth, participating mainly in vesicle trafficking and cytoskeleton rearrangements. This genesuperfamily has largely expanded in plants through evolution as compared with other Kingdoms, leadingto the suggestion that members of each subfamily might have acquired new functions associated toplant-specific processes. Legume plants engage in a nitrogen-fixing symbiotic interaction with rhizobia ina process that involves polar growth processes associated with the infection throughout the root hair. Toget insight into the evolution of small GTPases associated with this process, we use a comparativegenomic approach to establish differences in the Ras GTPase superfamily between legume and nonlegumeplants.Results: Phylogenetic analyses did not show clear differences in the organization of the differentsubfamilies of small GTPases between plants that engage or not in nodule symbiosis. Protein alignmentsrevealed a strong conservation at the sequence level of small GTPases previously linked to nodulation byfunctional genetics. Interestingly, one Rab and three Rop proteins showed conserved amino acidsubstitutions in legumes, but these changes do not alter the predicted conformational structure of theseproteins. Although the steady-state levels of most small GTPases do not change in response to rhizobia,we identified a subset of Rab, Rop and Arf genes whose transcript levels are modulated during thesymbiotic interaction, including their spatial distribution along the indeterminate noduleConclusions: This study provides a comprehensive study of the small GTPase superfamily in several plantspecies. The genetic program associated to root nodule symbiosis includes small GTPases to fulfill specificfunctions during infection and formation of the symbiosomes. These GTPases seems to have beenrecruited from members that were already present in common ancestors with plants as distant asmonocots since we failed to detect asymmetric evolution in any of the subfamily trees. Expressionanalyses identified a number of legume members that can have undergone neo- or sub-functionalizationassociated to the spatio-temporal transcriptional control during the onset of the symbiotic interaction.