Biology subjects

Moulia, B.

Publications and source records attributed to Moulia, B..

5 recordsLinked to original sources

bioRxiv2024

Differential warming at crown scale impacts walnut primary growth onset and secondary growth rate

Trees are exposed to significant spatio-temporal thermal variations, which can induce intracrown discrepancies in the onset and dynamics of primary and secondary growth. In recent decades, an increase in late winter and early spring temperatures has been observed, potentially accelerating bud break, cambial activation and their potential coordination. Intracrown temperature heterogeneities could lead to asymmetric tree shapes unless there is a compensatory mechanism at the crown level. An original warming experiment was conducted on young Juglans regia trees in a greenhouse. From February to August, the average temperature difference during the day between warmed and control parts was 4{degrees}C. The warming treatment advanced the date of budbreak significantly, by up to 14 days. Warming did not alter secondary growth resumption but increased growth rates, leading to higher xylem cell production (twice as many) and to an increase in radial increment (+80% compared to control). Meristems resumptions were asynchronous without coordination in response to temperature. Buds on warmed branches began to swell two weeks prior to cambial division, which was one week earlier than on control branches. A difference in carbon and water remobilisation at the end of bud ecodormancy was noted under warming. Overall, our results argue for a lack of compensatory mechanisms at the crown scale, which may lead to significant changes in tree architecture in response to intra-crown temperature heterogeneities. Highlight: When tree are submitted to asymmetrical warming, it leads to early budbreak and enhanced cambial activity for warmed branches

developmental biology↗

bioRxiv2020

Modelling the spatial crosstalk between two biochemical signals explains wood formation dynamics and tree-ring structure

In conifers, xylogenesis produces during a growing season a very characteristic tree-ring structure: large thin-walled earlywood cells followed by narrow thick-walled latewood cells. Although many factors influence the dynamics of differentiation and the final dimensions of xylem cells, the associated patterns of variation remain very stable from one year to the next. While radial growth is characterised by an S-shaped curve, the widths of xylem differentiation zones exhibit characteristic skewed bell-shaped curves. These elements suggest a strong internal control of xylogenesis. It has long been hypothesised that much of this regulation relies on a morphogenetic gradient of auxin. However, recent modelling works have shown that while this hypothesis could account for the dynamics of stem radial growth and the zonation of the developing xylem, it failed to reproduce the characteristic tree-ring structure. Here we investigated the hypothesis of a regulation by a crosstalk between auxin and a second biochemical signal, using dynamical modelling. We found that, in conifers, such a crosstalk is sufficient to simulate the characteristic features of wood formation dynamics, as well as the resulting tree-ring structure. In this model, auxin controls cell enlargement rates while another signal (e.g., cytokinin, TDIF) drives cell division and auxin polar transport. HighlightA dynamical model proves that two interacting signals (auxin, plus a cytokinin or the TDIF peptide) can drive wood formation dynamics and tree-ring structure development in conifers.

plant biology↗

bioRxiv2019

Transduction of mechanical cellular oscillation by the plasma-membrane mechanosensitive channel MSL10

Throughout their life, plants are submitted to recurrent cyclic mechanical loading due to wind. The resulting passive oscillation movements of stem and foliage is an important phenomenon for biological and ecological issues such as photosynthesis optimization 1-3 and thermal exchange 4. The induced motions at plant scale are well described and analyzed, with oscillations at typically 1 to 3 Hz in trees 5-10. However, the cellular perception and transduction of such recurring mechanical signals remains an open question. Multimeric protein complexes forming mechanosensitive (MS) channels embedded in the membrane provide an efficient system to rapidly convert mechanical tension into electrical signal 11. Here we show that the plasma membrane mechanosensitive channel MscS-LIKE 10 (MSL10) from the model plant Arabidopsis thaliana responds to pulsed membrane stretching with rapid activation and relaxation kinetics in the range of one second. Under sinusoidal membrane stretching MSL10 presents a greater activity than under static stimulation and behaves as a large bandpass oscillation \"follower\" without filtering the signal in the range of 0.3 to 3 Hz. With a localization in aerial organs naturally submitted to oscillations, our results suggest that the mechanosensitive channel MSL10 represents a molecular component of a universal system of oscillatory perception in plants.

plant biology↗

bioRxiv2018

How do alterations in root cap structure and integrity impact root responses to an increase in medium strength?

During root progression in soil, root cap cells are the first to encounter obstacles. The root cap is known to sense environmental cues, making it a relevant candidate for a mechanosensing site. An original two-layer medium was developed in order to study root responses to growth medium strength and the importance of the root cap in the establishment of these responses. Root growth and trajectory of primary roots of Arabidopsis thaliana seedlings were investigated using in vivo image analysis. After contact with the harder layer, the root either penetrated it or underwent rapid curvature, enabling reorientation of the root primary growth. The role of the root cap in tip reorientation was investigated by analyzing the responses of Arabidopsis mutant roots with altered caps. The primary root of fez-2 mutant lines, which has fewer root cap cell layers than wild-type roots, showed impaired penetration ability. Conversely, smb-3 roots of mutant lines, which display a higher number of root cap cells, showed enhanced penetration abilities. This work highlights that alterations in root cap shape and size affect the root responses to medium strength.\n\nHighlightThe analysis of the growth and orientation of Arabidopsis thaliana mutant roots affected in root cap size and shape showed that properly formed root cap is required to trigger the root responses to medium strength.\n\nAbbreviations

plant biology↗

bioRxiv2017

Ultradian Oscillation of Growth Reveals Regulatory Mechanism in the Straightening Movement of Wheat Coleoptile

To stand straight and upright along their growth, plants needs to regulate actively their posture. Gravitropic movement, which occurs when plants modify their growth and curvature to orient their aerial organ against the force of gravity, is a major feature of this postural control. A recent model has shown that graviception and proprioception are sufficient to account for the gravitropic movement and subsequent organ posture demonstrated by a range of species. However, some plants, including wheat coleoptiles, exhibit a stronger regulation of posture than predicted by the model. Here, we performed an extensive kinematics study on wheat coleoptiles during a gravitropic perturbation experiment in order to better understand this unexpectedly strong regulation. Close temporal observation of the data revealed that both perturbed and unperturbed coleoptiles showed oscillatory pulses of elongation and curvature variation that propagated from the apex to the base of their aerial organs. In perturbed (tilted) coleoptiles, we discovered a non-trivial coupling between the oscillatory dynamics of curvature and elongation. This relationship appears to be critical to the postural control of the organ, and indicates the presence of a mechanism that is capable of affecting the relationship between elongation rate, differential growth, and curvature.

plant biology↗