Biology subjects

Shabala, S.

Publications and source records attributed to Shabala, S..

3 recordsLinked to original sources

bioRxiv2021

A novel R3H protein, OsDIP1, confers ABA-mediated adaptation to drought and salinity stress in rice

Abscisic acid (ABA) is a key component of many signaling networks mediating plant adaptation to various stresses. In this context, ABA-induced antioxidant defence is considered to be a main mechanism to that enhances water stress tolerance in plants. The specific details of this activation remain, however, elusive. In this work, we show that DIP1, a protein from novel R3H family, played a central role in modulating water stress tolerance in rice. OsDIP1 transcripts were induced by hydrogen peroxide (H2O2), ABA, drought (polyethylene glycol treatment), and salt stress. Overexpression of OsDIP1 in rice enhanced drought and salinity tolerance while knocking out OsDIP1 by CRISPR-Cas9 editing resulted in drought and salt sensitive phenotype. The activity and gene expression of antioxidant defence enzymes, superoxide dismutase (SOD), catalase (CAT), increased in OsDIP1-overexpressed transgenic rice plants, while the content of malondialdehyde (MDA) decreased. In contrast, the content and gene expression of SOD and CAT, decreased, and the content of MDA increased in knockout of OsDIP1 rice plants, suggesting that overexpression of OsDIP1 enhances the antioxidant capacity of rice plants. The yeast two hybrid screening test revealed that OsDIP1 interacted with ZFP36, a key zinc finger transcription factor involved in ABA-induced antioxidant defence. Moreover, OsDIP1 could modulate some key ABA-responsive genes via interacting with ZFP36. Overall, our findings indicate an important role of OsDIP1 in ABA-induced antioxidant defence signaling and adaptation to salinity and drought in rice.

molecular biology↗

bioRxiv2021

Zoom in on Ca2+ pattern and ion flux dynamics to decode spatial and temporal regulation of cotton fiber growth

Cotton fibers are single-celled trichomes initiated from ovule epidermis prior to anthesis. Thereafter, the fibers undergo rapid elongation for 20 d before switching to intensive cell wall cellulose synthesis. The final length attained determines fiber yield and quality. As such, cotton fiber represents an excellent single cell model to study regulation of cell growth and differentiation, with significant agronomical implications. One major unresolved question is whether fiber elongation follows a diffusive or a tip growth pattern. We addressed this issue by using cell biology and electrophysiological approaches. Confocal imaging of Ca2+ binding dye, fluo-3 acetoxymethyl (Fluo-3), and in situ microelectrode ion flux measurement revealed that cytosolic Ca2+ was evenly distributed along the elongating fiber cells with Ca2+ and H+ fluxes oscillating from apical to basal regions of the elongating fibers. These findings demonstrate that, contrary to growing pollen tubes or root hairs, cotton fiber growth follows a diffusive, but not the tip growth, pattern. Further analyses showed that the elongating fibers exhibited substantial net H+ efflux, indicating a strong activity of the plasma membrane H+-ATPase required for energy dependent solute uptake. Interestingly, the growing cotton fibers were responding to H2O2 treatment, know to promote fiber elongation, by a massive increase in the net Ca2+ and H+ efflux in both tip and basal zones, while non-growing cells lacked this ability. These observations suggest that desensitization of the cell and a loss of its ability to respond to H2O2 may be causally related to the termination of the cotton fiber elongation. One sentence summaryConfocal imaging of Ca2+ patterning and in situ microelectrode ion flux measurements demonstrate that, contrary to growing pollen tubes or root hairs, cotton fiber growth follows a diffusive, but not the tip growth, pattern.

cell biology↗

bioRxiv2021

The AFB1 auxin receptor controls rapid auxin signaling and root growth through membrane depolarization in Arabidopsis thaliana

The existence of an electric gradient across membranes is essential for a cell operation. In plants, application of the growth regulator auxin (IAA) causes almost instantaneous membrane depolarization in various cell types, making membrane depolarization a hallmark of the rapid non-transcriptional responses to IAA. Auxin triggers rapid root growth inhibition; a process that underlies gravitropic bending. The growth and depolarization responses to auxin show remarkable similarities in dynamics, requirement of auxin influx and the involvement of the TIR1/AFB auxin coreceptors, but whether auxin-induced depolarization participates in root growth inhibition remains unanswered. Here, we established a toolbox to dynamically visualize membrane potential in vivo in Arabidopsis thaliana roots by combining the DISBAC2(3) fluorescent probe with microfluidics and vertical stage microscopy. This way we show that auxin-induced membrane depolarization tightly correlates with rapid root growth inhibition and that the cells of the transition zone/early elongation zone are the most responsive to auxin. Further, we demonstrate that auxin cycling in and out of the cells through AUX1 influx and PIN2 efflux is not essential for membrane depolarization and rapid root growth inhibition but acts as a facilitator of these responses. The rapid membrane depolarization by auxin instead strictly depends on the AFB1 auxin receptor, while the other TIR1/AFB paralogues contribute to this response. The lack of membrane depolarization in the afb1 mutant explains the lack of the immediate root growth inhibition. Finally, we show that AFB1 is required for the rapid depolarization and rapid growth inhibition of cells at the lower side of the gravistimulated root. These results are instrumental in understanding the physiological significance of membrane depolarization for the gravitropic response of the root and clarify the role of AFB1 as the receptor central for rapid auxin responses, adding another piece to the puzzle in understanding the biology of the phytohormone auxin.

plant biology↗