Biology subjects

Quintero, F. J.

Publications and source records attributed to Quintero, F. J..

2 recordsLinked to original sources

bioRxiv2022

Structure-Guided Identification of Critical Residues in the Vacuolar Na+,K+/H+ Antiporter NHX1 from Arabidopsis thaliana

Cation/Proton Antiporters (CPA) acting in all biological membranes help regulate the volume and pH of cells and of intracellular organelles. A key issue with these proteins is their structure-function relationships since they present intrinsic regulatory features that rely on structural determinants, including pH-sensitivity and the stoichiometry of ion exchange. Crystal structures are only available for prokaryotic CPA, whereas the eukaryotic ones have been modeled using the former as templates. Here we show an updated and improved structural model of the tonoplast-localized K+,Na+/H+ antiporter NHX1 of Arabidopsis as a representative of the vacuolar NHX family that is key to the accumulation of K+ into plant vacuoles. Conserved residues judged as functionally important were mutated and the resulting protein variants were tested for activity in the yeast Saccharomyces cerevisiae. Results indicate that residue N184 in the ND-motif characteristic of CPA1 could be replaced by the DD-motif of CPA2 family members with minimal consequences on activity, yet this residue may help to regulate the optimal pH range of the exchanger. Attempts to alter the electroneutrality of AtNHX1 by different combinations of amino acid replacements at N184, R353 and R390 residues resulted in inactive or partly active proteins with differential ability to control the vacuolar pH of the yeast.

plant biology↗

bioRxiv2021

A Calcium/Palmitoylation Switch Interfaces the Signaling Networks of Stress Response and Transition to Flowering

The precise timing of flowering in adverse environments is critical for plants to secure reproductive success. We report a novel mechanism controlling the time of flowering by which the palmitoylation-dependent nuclear import of protein SOS3/CBL4, a Ca2+-signaling intermediary in the plant response to salinity, results in the selective stabilization of the flowering time regulator GIGANTEA inside the nucleus under salt stress, while degradation of GIGANTEA in the cytosol releases the protein kinase SOS2 to achieve salt tolerance. S-acylation of SOS3 was critical for its nuclear localization and the promotion of flowering, but dispensable for salt tolerance. SOS3 interacted with the photoperiodic flowering components GIGANTEA and FKF1 on the CONSTANS gene promoter to sustain the transcription of CO and FT under salinity. Thus, SOS3 acts as a Ca2+- and palmitoylation-dependent molecular switch that fine-tunes flowering in a saline environment through the shared spatial separation and selective stabilization of GIGANTEA. The SOS3 protein connects two signaling networks to co-regulate stress adaptation and time of flowering. Short summaryS-acylation promoted the nuclear import of SOS3/CBL4 for the selective stabilization of the photoperiodic floral regulator GIGANTEA to fine-tune flowering time in a saline environment. Spatial separation of SOS3 acts as a molecular switch co-regulating stress adaptation and time of flowering.

plant biology↗