Biology subjects

Serre, N. B.

Publications and source records attributed to Serre, N. B..

4 recordsLinked to original sources

bioRxiv2022

The AUX1-AFB1-CNGC14 module establishes longitudinal root surface pH profile

Plant roots navigate in the soil environments following the gravity vector. Cell divisions in the meristem and rapid cell growth in the elongation zone propel the root tips through the soil. Actively elongating cells acidify their apoplast to enable cell wall extension by the activity of plasma membrane AHA H+-ATPases. The phytohormone auxin, central regulator of gravitropic response and root development, inhibits root cell growth, likely by rising the pH of the apoplast. However, the role of auxin in the regulation of the apoplastic pH gradient along the root tip is unclear. Here we show, by using an improved method for visualization and quantification of root surface pH, that the Arabidopsis thaliana root surface pH shows distinct acidic and alkaline zones, which are not primarily determined by the activity of AHA H+-ATPases. Instead, the distinct domain of alkaline pH in the root transition zone is controlled by a rapid auxin response module, consisting of the AUX1 auxin influx carrier, the AFB1 auxin co-receptor and the CNCG14 calcium channel. We demonstrate that the rapid auxin response pathway is required for an efficient navigation of the root tip.

plant biology↗

bioRxiv2021

ACORBA: Automated workflow to measure Arabidopsis thaliana root tip angle dynamic

Plants respond to the surrounding environment in countless ways. One of these responses is their ability to sense and orient their root growth toward the gravity vector. Root gravitropism is studied in many laboratories as a hallmark of auxin-related phenotypes. However, manual analysis of images and microscopy data is known to be subjected to human bias. This is particularly the case for manual measurements of root bending as the selection lines to calculate the angle are set subjectively. Therefore, it is essential to develop and use automated or semi-automated image analysis to produce reproducible and unbiased data. Moreover, the increasing usage of vertical-stage microscopy in plant root biology yields gravitropic experiments with an unprecedented spatiotemporal resolution. To this day, there is no available solution to measure root bending angle over time for vertical-stage microscopy. To address these problems, we developed ACORBA (Automatic Calculation Of Root Bending Angles), a fully automated software to measure root bending angle over time from vertical-stage microscope and flatbed scanner images. Moreover, the software can be used semi-automated for camera, mobile phone or stereomicroscope images. ACORBA represents a flexible approach based on both traditional image processing and deep machine learning segmentation to measure root angle progression over time. By its automated nature, the workflow is limiting human interactions and has high reproducibility. ACORBA will support the plant biologist community by reducing time and labor and by producing quality results from various kinds of inputs. Significance statementACORBA is implementing an automated and semi-automated workflow to quantify root bending and waving angles from images acquired with a microscope, a scanner, a stereomicroscope or a camera. It will support the plant biology community by reducing time and labor and by producing trustworthy and reproducible quantitative data.

plant 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↗

bioRxiv2019

Evidence for the involvement of protein lysine methylation in the response of sensitive and tolerant Arabidopsis species to cadmium stress

The mechanisms underlying the response and adaptation of plants to excess of trace elements are not fully described. Here, we analyzed the importance of protein lysine methylation for plants to cope with cadmium. We analyzed the effect of cadmium on lysine-methylated proteins and protein lysine methyltransferases (KMTs) in two cadmium-sensitive species, Arabidopsis thaliana and A. lyrata, and in three populations of A. halleri with contrasting cadmium accumulation and tolerance traits. We showed that some proteins are differentially methylated at lysine residues in response to Cd and that a few genes coding KMTs is regulated by cadmium. Also, we showed that nine out of 23 A. thaliana mutants interrupted in KMT genes have a tolerance to cadmium that is significantly different from that of wild-type seedlings. We further characterized two of these mutants, one was knocked-out in the calmodulin lysine methyltransferase gene and displayed increased tolerance to cadmium, the other was interrupted in a KMT gene of unknown function and showed a decreased capacity to cope with cadmium. Together, our results showed that lysine methylation of non-histone proteins is impacted by cadmium and that several methylation events are important for modulating the response of Arabidopsis plants to cadmium stress.

plant biology↗