Youssef Chebli

• PhD
• McGill University

The pollen tube is an extension of the male gametophyte in plants and mediates sexual reproduction by delivering the sperm cells to the female gametophyte. To accomplish this task, the elongating pollen tube must break through the thick wall of the pollen grain and penetrate multiple pistillar tissues. Both processes require the loosening of cell w...

The plant cell wall comprises various types of macromolecules whose abundance and spatial distribution change dynamically and are crucial for plant architecture. High-resolution live cell imaging of plant cell wall components is, therefore, a powerful tool for plant cell biology and plant developmental biology. To acquire suitable data, the experim...

Mechanoperception, the ability to perceive and respond to mechanical stimuli, is a common and fundamental property of all forms of life. Vascular plants such as Mimosa pudica use this function to protect themselves against herbivory. The mechanical stimulus caused by a landing insect triggers a rapid closing of the leaflets that drives the potentia...

The plant cell wall is an extracellular matrix that envelopes cells, gives them structure and shape, constitutes the interface with symbionts, and defends plants against external biotic and abiotic stress factors. The assembly of this matrix is regulated and mediated by the cytoskeleton. Cytoskeletal elements define where new cell wall material is...

Live cell imaging at high resolution of pollen tubes growing in vitro requires an experimental setup that maintains the elongated cells in a single optical plane and allows for controlled exchange of growth medium. As a low-cost alternative to lithography-based microfluidics, we developed a silicone-based spacer system that allows introducing spati...

Movie 2. Growing Camellia japonica pollen tube labeled with COS488 in liquid medium. The video is composed of maximum projection of z-stacks acquired over 20 time points with 1-min intervals. The time course experiment was performed using a Zeiss LSM 710 confocal microscope (doi.org/10.1111/jmi.12895).

Plant cell walls constitute the extracellular matrix surrounding plant cells and are composed mainly of polysaccharides. The chemical makeup of the primary plant cell wall, and specifically, the abundance, localization, and arrangement of the constituting polysaccharides are intimately linked with growth, morphogenesis, and differentiation in plant...

Movie 1. Growing Camellia japonica pollen tube stained with 1 µg/ml calcofluor white in liquid medium. The video is composed of maximum projection of z-stacks acquired over 20 time points with 1-min intervals. The right panel shows the bright field channel. The time course experiment was performed using a Zeiss spinning disk microscope (doi.org/10....

Simple plant cell morphologies, such as cylindrical shoot cells, are determined by the extensibility pattern of the primary cell wall, which is thought to be largely dominated by cellulose microfibrils, but the mechanism leading to more complex shapes, such as the interdigitated patterns in the epidermis of many eudicotyledon leaves, is much less w...

Polarized cell growth in plants is maintained under the strict control and exquisitely choregraphed balance of exocytic and endocytic membrane trafficking. The pollen tube has become a model system for rapid polar growth in which delivery of cell wall material and membrane recycling are controlled by membrane trafficking. Endocytosis plays an impor...

FRAP Experiments Show Pectate Lyases Promote Pollen Germination and Lubricate the Path of the Pollen Tube in Arabidopsis thaliana. - Volume 24 Supplement - Youssef Chebli, Anja Geitmann

Cell and organ morphogenesis in plants are regulated by the chemical structure and mechanical properties of the extracellular matrix, the cell wall. The two primary load bearing components in the plant cell wall, the pectin matrix and the cellulose/xyloglucan network, are constantly remodelled to generate the morphological changes required during p...

The constant force of gravity plays a primordial role in the ontogeny of all living organisms. Plants, for example, develop their roots and shoots in accordance with the direction of the gravitational vector. Any change in the magnitude and/or the direction of gravity has an important impact on the development of tissues and cells. In order to unde...

Cellular organelles move within the cellular volume and the effect of the resulting drag forces on the liquid causes bulk movement in the cytosol. The movement of both organelles and cytosol lead to an overall motion pattern called cytoplasmic streaming or cyclosis. This streaming enables the active and passive transport of molecules and organelles...

Plants are able to sense the magnitude and direction of gravity. This capacity is thought to reside in selected cell types within the plant body that are equipped with specialized organelles called statoliths. However, most plant cells do not possess statoliths, yet they respond to changes in gravitational acceleration. To understand the effect of...

Callose distribution under omnidirectional exposure to gravity. Confocal laser scanning micrographs of a pollen tube grown in omnidirectional-g labelled with (1→3)-β-glucan against callose. The three micrographs were taken from the same region of the pollen tube at different focal depths. Arrows indicate where the optical section is positioned cort...

Spatial distribution profile of cellulose and callose. Relative spatial distribution of cellulose (A) and callose (B) in Camellia pollen tubes grown at omnidirectional-g (orange), 1 g (blue), and hyper-g (2 g, 5 g, 7 g, 10 g and 14 g) represented by shades of red (cellulose) and green (callose) with darkest shade for highest g-value. Relative label...

The pollen tube is a cellular protuberance formed by the pollen grain, or male gametophyte, in flowering plants. Its principal metabolic activity is the synthesis and assembly of cell wall material which must be precisely coordinated to sustain the characteristic rapid growth rate and to ensure geometrically correct and efficient cellular morphogen...

Future space missions and implementation of permanent bases on Moon and Mars will greatly depend on the availability of ambient air and sustainable food supply. Therefore, understanding the effects of altered gravity conditions on plant metabolism and growth is vital for space missions and extra-terrestrial human existence. In this mini-review we s...

Cellular protuberance formation in walled cells requires the local deformation of the wall and its polar expansion. In many cells, protuberance elongation proceeds by tip growth, a growth mechanism shared by pollen tubes, root hairs, and fungal hyphae. We established a biomechanical model of tip growth in walled cells using the finite element techn...

Cellulose is the principal component of the load-bearing system in primary plant cell walls. The great resistance to tensile forces of this polysaccharide and its embedding in matrix components make the cell wall a material similar to a fiber composite. In the rapidly growing pollen tube, the amount of cellulose in the cell wall is untypically low....

One of the rare weak points of the model plant Arabidopsis is the technical problem associated with the germination of its male gametophyte and the generation of the pollen tube in vitro. Arabidopsis pollen being tricellular has a notoriously low in vitro germination compared to species with bicellular pollen. This drawback strongly affects the rep...

Future space missions and implementation of permanent bases on Moon and Mars will greatly depend on the availability of ambient air and sustainable food supply. Therefore, understanding the effects of micro-gravity on plant reproduction is vital for future extra-terrestrial human existence. Numerous studies have demonstrated the effect of gravity a...

Cellular growth and morphogenesis are central aspects of cellular differentiation. In plants, cellular growth is based on the turgor driven expansion of the cell wall and concomitant addition of new cell wall material. In no plant cell does this process occur as rapidly as in the pollen tube, the carrier of the male gametes. This cell is therefore...