Biology subjects

Ali, O.

Publications and source records attributed to Ali, O..

4 recordsLinked to original sources

bioRxiv2025

Outer epidermal edges mediate cell-cell adhesion for tissue integrity in plants

Cell-cell adhesion in plants is generally thought to be primarily mediated by the middle lamella, a supposedly thin adhesive layer of the cell wall. Here, we challenge this view. Through computational simulation we found that outer edges of cellular interfaces of the epidermis are hotspot for cell separating tensile stress. Characterization of the ultrastructure of those edges in planta revealed that they are locally thickened regions that harbor cellulose lamellae and pectin-based structural continuity across adjacent cells. We confirmed their dominant role for adhesion by studying mutants where those edges are defective and through direct mechanical testing. This reveals the key role of outer epidermal cell edges, rather than the middle lamella, in mediating cell-cell adhesion for tissue integrity in plants.

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↗

bioRxiv2020

Rapid evolution drives the rise and fall of carbapenem resistance during an acute Pseudomonas aeruginosa infection

It is well established that antibiotic treatment selects for resistance in pathogenic bacteria. However, the evolutionary responses of pathogen populations to antibiotic treatment during infections remain poorly resolved, especially in acute infections. Here we map the evolutionary responses to treatment in high definition through genomic and phenotypic characterization of >100 isolates from a patient with P. aeruginosa pneumonia. Antibiotic therapy (meropenem, colistin) caused a rapid crash of the P. aeruginosa population in the lung, but this decline was followed by the spread of meropenem resistance mutations that restrict antibiotic uptake (oprD) or modify LPS biosynthesis (wbpM). Low fitness strains with high-level meropenem resistance (oprD) were then replaced by high fitness strains with anti-resistance mutations in the MexAB-OprM efflux pump, causing a rapid decline in resistance to both meropenem and a collateral loss of resistance to a broad spectrum of antibiotics. In contrast, we did not observe any evolutionary responses to antibiotic treatment in the intestinal population of P. aeruginosa. Carbapenem antibiotics are key to the treatment of infections caused by Gram negative pathogens, and our work highlights the ability of natural selection to drive both the rapid rise and fall of carbapenem resistance during acute infections.

evolutionary biology↗

bioRxiv2019

A microtubule-mediated mechanical feedback controls leaf blade development in three dimensions

Many plant species have thin leaf blades, which is an important adaptation that optimizes the exchanges with the environment. Here, we provide evidence that their three-dimensional geometry is governed by microtubule alignment along mechanical stress patterns in internal walls. Depending on the primary shape of the primordium, this process has the potential to amplify an initial degree of flatness, or promote the formation of nearly axisymmetric, mostly elongating organs, such as stems and roots. This mechanism may explain leaf evolution from branches, which is alternative to Zimmermanns influential, but widely questioned, telome theory.\n\nOne Sentence SummaryMechanical feedback controls leaf development in three dimensions

developmental biology↗