Biology subjects

Landrein, B.

Publications and source records attributed to Landrein, B..

9 recordsLinked to original sources

bioRxiv2025

APETALA2 controls seed growth by regulating outer integument mechanical identity during seed coat differentiation

Organ morphogenesis requires differentiating cells to acquire mechanical properties that precisely regulate growth. In Arabidopsis thaliana, seed size and shape are largely controlled by the outer integument of the seed coat, whose two layers develop distinct mechanical behaviors critical for growth regulation. Here, we show that the cell identity factor APETALA2 (AP2) both promotes and restricts seed growth by coordinating the post-fertilization differentiation of these layers into distinct seed coat tissues. AP2 drives layer-specific remodeling of cell wall composition, notably affecting pectin and xyloglucan, thereby establishing contrasting mechanical properties between the two layers. Unexpectedly, these changes in wall composition and mechanics do not alter mechanosensitive responses, revealing a surprising uncoupling between cell wall remodeling and mechanotransduction. Our findings identify AP2 as a key coordinator of tissue-specific mechanical differentiation during organ morphogenesis.

plant biology↗

bioRxiv2025

An embryo-derived peptide signal directs endosperm polarity in Arabidopsis

Angiosperm seed formation requires the coordinated development of the products of double fertilization, the embryo and the endosperm. The endosperm mediates efficient nutrient transfer from surrounding maternal tissues to the developing embryo. This function requires a polarized tissue organization, which manifests as early polar gene expression and polar cellularization dynamics. We show that the receptor kinase HAIKU2 acts in coordination with the transcription factor WRKY10/MINISEED3 to ensure robust endosperm polarity establishment through the activity of the homeodomain transcription factors WUSCHEL-RELATED HOMEOBOX 8 and 9. This process depends on egg cell fertilization and is mediated through the peptide PATHOGEN-INDUCED PEPTIDE-LIKE 7, which acts as a HAIKU2 ligand. Our results reveal how a molecular paracrine dialogue between the embryo and endosperm ensures optimal seed developmental coordination.

plant biology↗

bioRxiv2025

Plasticity and invariance of Arabidopsis inflorescence and floral shoot apical meristems in response to mineral nutrients

In many species, floral organ production is invariant while flower production rate can be plastic. This allows plants to adapt flower number to their environment whilst maintaining a constant flower structure. The CLAVATA/WUSCHEL feedback loop underpins both inflorescence (IM) and floral meristem (FM) activity, respectively responsible for flower and floral organ production. We explore how plasticity and invariance can differ between IM and FM in response to nutrient availability. FM size is less sensitive to changes in nutrients than IM size, and floral organ production is insensitive to these small size changes. However, clavata3 mutants display larger changes in FM size, approaching those observed in WT IM under nutrient change, with increased floral organ number. This suggests that invariant floral organ production requires that FM size undergoes limited changes in response to nutrients. Compared to the IM, in the FM, levels of cytokinin (CK) signaling are lower and CK signaling and WUSCHEL expression are less impacted by nutrient level. Through genetic perturbations, we show a reduced response of FMs to varying cytokinin levels. Our work shows one way that the balance between plasticity and invariance can be set differently in different contexts.

plant biology↗

bioRxiv2024

Long-term high temperatures affect seed maturation and seed coat integrity in Brassica napus

Temperatures above the optimum growth threshold affect seed development, accelerating embryo development and producing seeds with ruptured seed coats. However, the underlying mechanisms of this effect remain unclear. To investigate temperature-induced seed coat rupture, we used a multidisciplinary approach combining detailed phenotyping, transcriptomics, histology, immunolabelling, cell wall profiling and nanoindentation-based mechanics of the seed coat in oilseed rape (Brassica napus). Our data reveal that high temperatures accelerate embryo growth, resulting in larger embryos without a compensatory increase in overall seed size. This rapid embryo expansion may exert elevated mechanical stress on the seed coat cells, significantly thinning the seed coat layers. Concurrently, prolonged exposure to high temperatures drives premature biochemical maturation of the seed coat, characterized by accumulation of demethylesterified pectin. Nanoindentation analysis demonstrated that these changes may have compromised the structural integrity of seed coat cell walls. Ultimately, the weakened seed coat may not withstand the internal tension imposed by the fast-growing embryo, leading to seed coat rupture and reduced seed quality. Our work on seed maturation and the mechanism of heat-induced seed coat rupture provides valuable insights for future research into breeding thermotolerant Brassica napus, crucial in the context of a changing climate. HIGHLIGHTSO_LIGrowth of Brassica napus under long-term high temperatures accelerated embryo growth and led to seed coat rupture in approximately half of the seeds. C_LIO_LIPathways linked to cell wall modification were found to be significantly differentially regulated at high temperatures, accompanied by increased pectin demethylesterification in the seed coat. C_LIO_LIA lower reduced modulus and hardness indicate that the surface of HT seeds is mechanically more compliant and softer. Together with the reduced thickness of the seed coat layers, such a seed coat, as a whole structure, is mechanically weaker and less able to resist deformation imposed by embryo growth, resulting in seed coat rupture. C_LI

plant biology↗

bioRxiv2023

Spatiotemporally distinct responses to mechanical forces shape the developing seed of Arabidopsis

Organ morphogenesis depends on mechanical interactions between cells and tissues. These interactions generate forces that can be sensed by cells and affect key cellular processes. However, how mechanical forces contribute, together with biochemical signals, to the shaping of complex organs is still unclear. We address this question using the seed of Arabidopsis as a model system. We show that seeds first experience a phase of high anisotropic growth that is dependent on the response of cortical microtubule (CMT) to forces, which guide cellulose deposition according to shape-driven stresses in the outermost layer of the seed coat. However, at later stages of development, we show that seed growth is isotropic and depend on the properties of an inner layer of the seed coat that stiffens its walls in response to tension but has isotropic material properties. Finally, we show that the transition from anisotropic to isotropic growth is due to dampening of CMT responses to shape-driven stresses. Altogether, our work support that spatiotemporally distinct mechanical responses control the shape of developing seeds in Arabidopsis.

plant biology↗

bioRxiv2023

Sugar signaling modulates SHOOT MERISTEMLESS expression and meristem function in Arabidopsis

In plants, development of all above-ground tissues is controlled by the shoot apical meristem (SAM) which balances cell proliferation and differentiation to allow life-long growth. To maximize fitness and survival, meristem activity is adjusted to the prevailing conditions through a poorly understood integration of developmental signals with environmental and nutritional information. Here, we show that sugar signals influence SAM function by altering the protein levels of SHOOT MERISTEMLESS (STM), a key regulator of meristem maintenance. STM is less abundant in the inflorescence meristems of plants grown or treated under limiting light conditions, with lower STM levels correlating with lower sugar content in these meristems. Additionally, sucrose but not light is sufficient to sustain STM accumulation in excised inflorescences. Plants overexpressing the 1-subunit of SUCROSE-NON-FERMENTING1-RELATED KINASE 1 (SnRK1) accumulate less STM protein under optimal light conditions, despite higher sugar accumulation in the meristem. Furthermore, SnRK11 interacts physically with STM, suggesting a direct local repression. Surprisingly, silencing SnRK1 in the meristem leads to reduced STM expression and severe developmental phenotypes previously associated with STM loss-of-function. Altogether, we demonstrate that sugars promote STM accumulation and that the SnRK1 sugar sensor plays a dual role in the SAM, limiting STM abundance under unfavorable conditions but being required for overall meristem organization and integrity. This highlights the importance of sugars and SnRK1 signaling for the proper coordination of meristem activities.

plant biology↗

bioRxiv2021

Endosperm turgor pressure both promotes and restricts seed growth and size

Organ size depends on complex biochemical and mechanical interactions between cells and tissues. Here, we investigate the control of seed size, a key agronomic trait, by mechanical interactions between two compartments: the endosperm and the testa. By combining experiments with computational modelling, we tested an incoherent mechanical feedforward loop hypothesis in which pressure-induced stresses play two antagonistic roles; directly driving seed growth, but indirectly inhibiting it through mechanosensitive stiffening of the seed coat. We show that our model can recapitulate wild type growth patterns and explain the small seed phenotype of the haiku2 mutant. Our work further reveals that the developmental regulation of endosperm pressure is needed to prevent a precocious reduction of seed growth rate induced by force-dependent seed coat stiffening.

plant biology↗

bioRxiv2017

A model of protein interactions for regulating plant stem cells

The plant shoot apical meristem holds a stem cell niche from which all aerial organs originate. Using a computational approach we show that a mixture of monomers and heterodimers of the transcription factors WUSCHEL and HAIRY MERISTEM is sufficient to pattern the stem cell niche, and predict that immobile heterodimers form a regulatory pocket surrounding the stem cells. The model achieves to reproduce an array of perturbations, including mutants and tissue size modifications. We also show its ability to reproduce the recently observed dynamical shift of the stem cell niche during the development of an axillary meristem. The work integrates recent experimental results to answer the longstanding question of how the asymmetry of expression between the stem cell marker CLAVATA3 and its activator WUSCHEL is achieved, and recent findings of plasticity in the system.

plant biology↗

bioRxiv2017

Nitrate modulates stem cell dynamics by regulating WUSCHEL expression through cytokinins

The shoot apical meristem (SAM) is responsible for the generation of all of the aerial parts of plants1. Given its critical role, dynamical changes in SAM activity should play a central role in the adaptation of plant architecture to the environment2. Using quantitative microscopy, grafting experiments and genetic perturbations, we connect the plant environment to the SAM, by describing the molecular mechanism by which cytokinins signal the level of nutrient availability to the SAM. We show that a systemic signal of cytokinin precursors3 mediates the adaptation of SAM size and organogenesis rate to the availability of mineral nutrients by modulating the expression of WUSCHEL, a key regulator of stem cell homeostasis4. In time-lapse experiments, we further show that this mechanism allows meristems to adapt to rapid changes in nitrate concentration, and thereby modulate their rate of organ production to the availability of mineral nutrients within a few days. Our work sheds new light on the role of the stem cell regulatory network, by showing that it does not only maintain meristem homeostasis but also allows plants to adapt to rapid changes in the environment.

plant biology↗