Biology subjects

Kubalova, M.

Publications and source records attributed to Kubalova, M..

3 recordsLinked to original sources

bioRxiv2025

POLYGALACTURONASES REGULATED BY AUXIN facilitate root cell elongation in Arabidopsis thaliana via pectin remodeling

Root cell elongation, the main driver of root growth, is tightly associated with cell wall remodeling, particularly through pectin modifications, which facilitate cell wall loosening and strengthening while maintaining structural integrity. Root cell elongation is precisely regulated by the phytohormone auxin, which has long been known to inhibit this process. The molecular pathways through which auxin influences cell wall modifications remain poorly understood. In this study, we explore the transcriptional regulation of cell wall-related genes by auxin in Arabidopsis thaliana roots. The nuclear auxin pathway altered the expression of numerous cell-wall related genes, suggesting dynamic modification of the cell wall during root cell elongation. We identified novel root-specific polygalacturonases (PGs), enzymes involved in pectin degradation, which we termed POLYGALACTURONASES REGULATED BY AUXIN (PGRAs). PGRAs are expressed specifically in the root epidermis, beginning at the elongation zone. Our results demonstrate that induction of PGRA1 expression initially promotes root cell elongation, while long term overexpression inhibits root growth. Auxin downregulates PGRA1 in the elongation zone, and plants lacking PGRAs fail to increase root growth rate in response to reduced auxin levels. This suggests that auxin downregulates PGRA expression to prevent PGRA-mediated pectin remodeling, thereby contributing to inhibition of root cell elongation. We established a novel link between auxin signaling and pectin modifications in the control of cell growth. These findings provide new insights into the molecular mechanisms through which auxin regulates root cell elongation, highlighting the role of pectin matrix modifications in this process.

plant biology↗

bioRxiv2025

Gibberellin-deactivating GA2OX enzymes act as a hub for auxin-gibberellin crosstalk in Arabidopsis thaliana root growth regulation

Plant bodies are built from immobile cells, making the regulation of cell expansion essential for growth, development, and adaptation. In roots, cell elongation executes the movement of the root tips through soil. This process is tightly controlled by numerous signaling pathways. Among these, gibberellin and auxin signaling stand out for their contrasting effects on root growth, interacting through complex crosstalk at multiple regulatory levels. Here we reveal the molecular basis of the auxin-gibberellin crosstalk in the model plant Arabidopsis thaliana. We show that auxin signaling pathway steers the expression of GIBBERELLIN 2-OXIDASES (GA2OX), key gibberellin-deactivating enzymes in the root elongation zone. GA2OX are negative regulators of root cell elongation; GA2OX8 overexpression decreases gibberellin levels and inhibits root cell elongation, in contrast, the ga2ox heptuple mutant roots show elevated gibberellin levels in the elongation zone and grow longer roots. Shoot derived auxin can regulate GA2OX8 expression in roots, linking systemic auxin signaling to local gibberellin modulation. In addition, GA2OX8 is active in vascular tissues and the stem cell niche, tissues with high auxin levels. Loss of GA2OX genes results in altered stem cell niche, including increased quiescent center size and expanded root cell layers, highlighting the role of these enzymes in maintaining tissue organization. Together, our findings identify GA2OX6 and GA2OX8 enzymes as key mediators of auxin-gibberellin crosstalk, providing insights into their roles in root elongation, vascular development, and stem cell niche maintenance. These results expand our understanding of how auxin integrates with gibberellin signaling to coordinate root development and growth dynamics.

plant biology↗

bioRxiv2023

Auxin coreceptor IAA17/AXR3 controls cell elongation in Arabidopsis thaliana root by modulation of auxin and gibberellin perception

The nuclear TIR1/AFB - Aux/IAA auxin pathway plays a crucial role in regulating plant growth and development. Specifically, the IAA17/AXR3 protein participates in root development, and the accumulation of its mutant variant, AXR3-1, which cannot bind auxin, leads to severe root growth phenotype and agravitropism. However, the mechanism by which AXR3 regulates cell elongation is not fully understood. Here we show that the inducible expression of AXR3-1 in the Arabidopsis thaliana root triggers excessive cell elongation that is followed by growth arrest of the root. We exploited this effect to reveal the underlying molecular mechanism of AXR3 action. We show that AXR3-1 acts exclusively in the nucleus where it interferes with the nuclear auxin transcriptional pathway, while the rapid cytoplasmic auxin root growth response is not affected. The analysis of the transcriptome of the induced AXR3-1 roots revealed changes in phytohormone perception and homeostasis. We show that the accumulation of AXR3-1 disturbs auxin homeostasis which leads to excessive auxin accumulation. At the same time, the reaction of the AXR3-1 roots to gibberellin is altered. These results show that the IAA17/AXR3 maintains an optimal cell elongation rate by controlling the auxin response, auxin homeostasis and the interplay with gibberellin signaling.

plant biology↗