Biology subjects

Alvarez-Fernandez, A.

Publications and source records attributed to Alvarez-Fernandez, A..

5 recordsLinked to original sources

bioRxiv2026

IRON DEFICIENCY RESHAPES THE POPLAR ROOT AND EXUDATE METABOLITE PROFILES AND DRIVES EXUDATE-MEDIATED IRON MOBILIZATION

Iron (Fe) deficiency under alkaline conditions limits Fe bioavailability and reshapes plant metabolism. We asked how Fe deficiency at pH 7.5 alters the metabolite profiles of roots and root exudates of Populus x canescens, and whether exudates mobilize Fe at high pH. Hydroponically grown plants were deprived of Fe for 20 and 27 days. Roots and exudates, collected in nutrient solution and in distilled water, were profiled by UHPLC-QTOF MS, and metabolites were annotated using MS/MS molecular networking (MetGem) and public spectral libraries. Fe deficiency caused significant global shifts in both root and exudate metabolomes. In roots, phenylpropanoids increased at 27 days (proanthocyanidins, neochlorogenic acid, naringenin), whereas the salicylate glycoside salicortin decreased, suggesting a redirection of phenylpropanoid flux. In nutrient-solution exudates, eight flavonoids, including quercitrin, accumulated strongly at 27 days, and catecholic coumarins such as fraxetin were detected in roots and exudates. Exudates from Fe-deficient plants increased Fe mobilization from Fe(III) oxides at pH 7.5, and quercitrin solubilized Fe as efficiently as fraxetin. Alkaline Fe deficiency thus reconfigures poplar root and exudate metabolomes, and exuded flavonoids, not only coumarins, may contribute to Fe mobilization at high pH.

plant biology↗

bioRxiv2026

Redox-active di-O-methylated coumarins exudation contributes to genotype-dependent iron deficiency tolerance in soybean

Iron (Fe) deficiency is a widespread disorder limiting global soybean (Glycine max (L.) Merr.) production. Although root exudation is a key adaptive mechanism for Fe scarcity in species like Arabidopsis, a detailed chemical characterization of soybean exudates is lacking. Here, we examined the accumulation and secretion of phenolic compounds in soybean roots and their correlation with intraspecific tolerance to Fe-deficiency chlorosis. Seven soybean genotypes with contrasting tolerance, derived from U.S. breeding programs, were analyzed. Root exudates from Fe-deficient soybean plants solubilized ferric oxide. We identified and quantified 28 coumarin-type phenolics, with catechol methylsideretin as the predominant component. Although the qualitative coumarin profile was consistent across all genotypes, Fe-efficient lines secreted these compounds at higher levels or earlier during Fe deficiency than Fe-inefficient lines. The efficient genotype A7 showed coordinated upregulation of coumarin biosynthesis and secretion, whereas this response was weaker in the Fe-inefficient genotype IsoClark. Catechol methylsideretin concentrations strongly correlated with the ability of root exudates to mobilize Fe from ferric oxide. The conserved phenolic profile, together with divergence from those reported in non-legume species, suggests lineage-specific adaptations and ecological roles beyond Fe mobilization. These results highlight genotype-dependent exudation as a determinant of soybean Fe-deficiency tolerance, with implications for breeding. HIGHLIGHTIron deficiency induces soybean root exudates containing predominantly catechol methylsideretin which mobilize iron; genotypes differing in Fe efficiency show conserved qualitative but contrasting quantitative coumarin profiles.

plant biology↗

bioRxiv2025

Genomic connectivity and adaptation signals of the freshwater sponge Ephydatia muelleri across its distribution

1.Freshwater sponges fulfill critical ecological functions, including maintaining water quality, regulating nutrient dynamics, offering habitats for diverse taxa, and serving as a vital food source for various species. However, their patterns of dispersal and genetic connectivity remain inadequately understood, posing significant challenges to effective conservation assessments. We examined genetic connectivity and genetic adaptation to local environmental conditions in Ephydatia muelleri across its geographic range using ddRADseq-derived SNPs from 106 individuals collected from 11 localities spanning North America, Europe, and Asia. Analysis of 3,182 neutral SNPs revealed low connectivity and strong genetic structure among regions within two main genetic clusters of North America and Eurasia, while 115 SNPs identified to be under selection showed considerable evidence for differentiated, polygenic adaptation to light and temperature conditions across sampled locations, as well as selection on gene regulatory processes. These findings align with the "monopolization hypothesis", suggesting that historical climatic and geological conditions of the Last Glacial Maximum, including habitat expansion, contraction, and natural barriers, have contributed more to the current genetic structure of E. muelleri populations than contemporary gene flow, which is restricted by monopolistic habitat colonization by this species. Our results provide novel support for ecological theory on dispersal in aquatic invertebrates, as well as insights into the plasticity of E. muelleri in the face of varying environmental conditions that are fundamentally important for freshwater ecosystem conservation.

evolutionary biology↗

bioRxiv2019

Medicago truncatula Yellow Stripe1-Like3 gene is involved in symbiotic nitrogen fixation

Symbiotic nitrogen fixation carried out in legume root nodules requires transition metals. These nutrients are delivered by the host plant to the endosymbiotic nitrogen-fixing bacteria living with the nodule cells, a process in which vascular transport is essential. As occurs in root-to-shoot transport, members of the Yellow Stripe-Like (YSL) family of metal transporters should also be required for root-to-nodule metal delivery. The genome of the model legume Medicago truncatula encodes for eight YSL proteins, four of them with a high degree of similarity to Arabidopsis thaliana YSLs involved in long-distance metal trafficking. Among them, MtYSL3 is a plasma membrane protein expressed by vascular cells in roots and nodules, and by cortical nodule cells. Reducing expression levels of this gene had no major effect on plant physiology when assimilable nitrogen was provided in the nutrient solution. However, nodule functioning was severely impaired, with a significant reduction of nitrogen fixation capabilities. Further, iron and zinc accumulation and distribution changed. Iron was retained in the apical region of the nodule, while zinc became strongly accumulated in the nodule veins in the ysl3 mutant. These data suggest a role of MtYSL3 in vascular delivery of iron and zinc to symbiotic nitrogen fixation. HighlightMedicago truncatula YSL3 transporter is required for optimal nitrogen fixation in root nodules, mediating iron and zinc distribution in these organs.

plant biology↗

bioRxiv2019

Nicotianamine synthase 2 is required for symbiotic nitrogen fixation in Medicago truncatula nodules

Symbiotic nitrogen fixation carried out by the interaction between legumes and diazotrophic bacteria known as rhizobia requires of relatively large levels of transition metals. These elements act as cofactors of many key enzymes involved in this process. Metallic micronutrients are obtained from soil by the roots and directed to sink organs by the vasculature, in a process participated by a number of metal transporters and small organic molecules that mediate metal delivery in the plant fluids. Among the later, nicotianamine is one of the most important. Synthesized by nicotianamine synthases (NAS), this non-proteinogenic amino acid forms metal complexes participating in intracellular metal homeostasis and long-distance metal trafficking. Here we characterized the NAS2 gene from model legume Medicago truncatula. MtNAS2 is located in the root vasculature and in all nodule tissues in the infection and fixation zones. Symbiotic nitrogen fixation requires of MtNAS2 function, as indicated by the loss of nitrogenase activity in the insertional mutant nas2-1, a phenotype reverted by reintroduction of a wild-type copy of MtNAS2. This would be the result of the altered iron distribution in nas2-1 nodules, as indicated by X-ray fluorescence studies. Moreover, iron speciation is also affected in these nodules. These data suggest a role of nicotianamine in iron delivery for symbiotic nitrogen fixation.\n\nSignificance StatementNicotianamine synthesis mediated by MtNAS2 is important for iron allocation for symbiotic nitrogen fixation by rhizobia in Medicago truncatula root nodules.

plant biology↗