Biology subjects

Portes, M. T.

Publications and source records attributed to Portes, M. T..

4 recordsLinked to original sources

bioRxiv2026

ER-located Ca2+ ATPase ACA2 regulates Ca2+ cytoplasmic pool linked to root hair growth in Arabidopsis thaliana

Root hairs (RH) are excellent model systems for studying cell size and polarity since they elongate several hundred-fold their original size. Their tip growth is regulated by both intrinsic and environmental signals and is associated with the existence of a highly controlled cytoplasmic tip Ca{superscript 2} gradient, whose disruption impairs RH development. The molecular mechanisms underlying the Ca2+ homeostasis fine tuning and the Ca2+ organellar contributions to the cytoplasmic pool remain unclear. In the model plant Arabidopsis thaliana, many efflux routes are present, including those that employ Ca2+-pumps from the Autoinhibited Ca2+-ATPase (ACA) family. Here, we identified that the ER localized ACA2, and to a lower extent ACA7, are crucial ACAs required to control RH growth. By using genetically encoded Ca2+ biosensors we showed that Ca2+-dynamics are compromised in the aca2-2 mutant, having lower cytosolic Ca2+ concentration [Ca2+]cyt and growth rate, showing an altered homeostatic calcium setpoint compared to Col-0. Accordingly, the ACA2 mutation changed the dynamics of [Ca2+]cyt oscillations coupled to growth rate, inducing longer periods and more regular oscillations in the dominant high-frequency range (around 22 s), and slower oscillations (around 1 min) in the low-frequency range. Finally, expression of ACA2 with changes in four putative Ca2+ binding residues (ACA2{Delta}Ca2+) failed to rescue the RH growth phenotype in the aca2-2 mutant. Collectively, our findings indicate that ER-localized ACA2 and possibly ACA7 are crucial for modulating cytoplasmic Ca2+ signals, possibly composing a critical part of a negative feedback loop, and their absence leads to impairments in RH cell elongation.

plant biology↗

bioRxiv2025

Exposure time to moderately high temperature affects photosynthetic response to water deficit in Eucalyptus globulus Labill.

The co-occurrence of drought and heat stress in the field is especially frequent and the plant response to a combination of these abiotic stresses is singular, remaining largely unknown. Understanding physiological responses to a combined stress is of particular importance in face of the imminent global climate changes, which is predicted to entail not only higher temperatures, but also increase in drought, imposing restrictions to the productivity of economically important species as E. globulus. This forest species is critically affected by changes in temperature and water availability, since its high productivity implies in high rates of water use. In order to evaluate the photosynthetic responses of Eucalyptus globulus to these environmental conditions, young plants were grown at 25{degrees} C and 35{degrees} C under different irrigation regimes: full irrigation - FI, moderate drought - MD, and severe drought - SD. Plants grown at 25{degrees} C FI and MD were also subjected to a short-term exposure to 35{degrees} C. Several ecophysiological variables, derived mainly from leaf gas exchange and chlorophyll a fluorescence measurements, were compared in order to test the hypotheses that: i) E. globulus show different responses to short or long-term exposure to 35{degrees} C; ii) the effect of both stresses combined will not be simply the sum of each condition applied separately. Our results showed that plants respond differently to water deficit according to the thermal regime. The combination of water deficit and a long-term exposure to 35{degrees} C caused a down-acclimation of the photosynthetic capacity, while plants under the short-term treatment showed a higher performance, even when compared to the 25{degrees} C control condition, supporting the hypothesis i. Thus, the short-term exposure to 35{degrees} C induced an increase in tolerance to water deficit. Since the response to a combination of heat and drought differed from the superposition of individual responses, as observed mainly at 35{degrees} C, the hypothesis ii was also supported by our results.

plant biology↗

bioRxiv2024

The Genetic Puzzle of Multicopy Genes: Challenges and Troubleshooting

BackgroundStudies with multicopy genes impose challenges related to gene redundancy and sequence similarity among copies. Recent advances in molecular biology and genomics tools associated with dedicated databases facilitate their study. Thus, the present work emphasizes the need for rigorous methodologies and standardized approaches to interpret RT-qPCR results accurately. ResultsThe present work in Physcomitrium patens provides a comprehensive five-step protocol, using thiamine thiazole synthase (THI1) and sucrose 6-phosphate phosphohydrolase (S6PP) genes as proof of concept, to showcase a systematic workflow for studying multicopy genes. Beyond examining genes of interest, we highlight the critical role of choosing appropriate internal controls in the analytical process for accurately interpreting gene expression patterns. We emphasized the importance of identifying the most relevant orthologous gene, recognizing the inherent challenges in determining the most functional copy for subsequent studies. Our objective is to enhance comprehension of gene redundancy by dissecting multicopy genes genomic landscape and its characteristics. Furthermore, we address the decision-making process surrounding the quantification of expression levels of multicopy genes. ConclusionsThe study of multicopy genes discloses early events of functional adaptation. We emphasize the significance of multicopy genes in plant biology and provide a practical protocol for their study. Plant systems are strongly influenced by light/dark cycles, and the challenges inherent to this process are acknowledged. In conclusion, our comprehensive approach aims to advance the understanding of multicopy gene dynamics, offering practical methodologies and contributing valuable insights to the scientific community.

molecular biology↗

bioRxiv2019

The Arabidopsis Diacylglycerol Kinase 4 is involved in nitric oxide-dependent pollen tube guidance and fertilization

Nitric oxide (NO) is a key signaling molecule that regulates diverse biological processes in both animals and plants. In animals, NO regulates vascular wall tone, neurotransmission and immune response while in plants, NO is essential for development and responses to biotic and abiotic stresses [1-3]. Interestingly, NO is involved in the sexual reproduction of both animals and plants mediating physiological events related to the male gamete [2, 4]. In animals, NO stimulates sperm motility [4] and binding to the plasma membrane of oocytes [5] while in plants, NO mediates pollen-stigma interactions and pollen tube guidance [6, 7]. NO generation in pollen tubes (PTs) has been demonstrated [8] and intracellular responses to NO include cytosolic Ca2+ elevation, actin organization, vesicle trafficking and cell wall deposition [7, 9]. However, the NO-responsive proteins that mediate these responses are still elusive. Here we show that PTs of Arabidopsis lacking the pollen-specific Diacylglycerol Kinase 4 (DGK4) grow slower and become insensitive to NO-dependent growth inhibition and re-orientation responses. Recombinant DGK4 protein yields NO-responsive spectral and catalytic changes in vitro which are compatible with a role in NO perception and signaling in PTs. NO is a fast, diffusible gas and, based on our results, we hypothesize it could serve in long range signaling and/or rapid cell-cell communication functions mediated by DGK4 downstream signaling during the progamic phase of angiosperm reproduction.

plant biology↗