Correction: Massively Parallelized Pollen Tube Guidance and Mechanical Measurements on a Lab-on-a-Chip Platform
[This corrects the article DOI: 10.1371/journal.pone.0168138.].
Massively Parallelized Pollen Tube Guidance and Mechanical Measurements on a Lab-on-a-Chip Platform
Pollen tubes are used as a model in the study of plant morphogenesis, cellular differentiation, cell wall biochemistry, biomechanics, and intra- and intercellular signaling. For a “systems-understanding” of the bio-chemo-mechanics of tip-polarized growth in pollen tubes, the need for a versatile, experimental assay platform for quantitative data collection and analysis is critical. We introduce a Lab-on-a-Chip (LoC) concept for high-throughput pollen germination and pollen tube guidance for parallelized optical and mechanical measurements. The LoC localizes a large number of growing pollen tubes on a single plane of focus with unidirectional tip-growth, enabling high-resolution quantitative microscopy. This species-independent LoC platform can be integrated with micro-/nano-indentation systems, such as the cellular force microscope (CFM) or the atomic force microscope (AFM), allowing for rapid measurements of cell wall stiffness of growing tubes. As a demonstrative example, we show the growth and directional guidance of hundreds of lily (Lilium longiflorum) and Arabidopsis (Arabidopsis thaliana) pollen tubes on a single LoC microscopy slide. Combining the LoC with the CFM, we characterized the cell wall stiffness of lily pollen tubes. Using the stiffness statistics and finite-element-method (FEM)-based approaches, we computed an effective range of the linear elastic moduli of the cell wall spanning the variability space of physiological parameters including internal turgor, cell wall thickness, and tube diameter. We propose the LoC device as a versatile and high-throughput phenomics platform for plant reproductive and development biology using the pollen tube as a model.
Creeping walls, softening fruit, and penetrating pollen tubes: the growing roles of expansins.
The differences in form and texture between a slime mold and a redwood tree originate, in large part, from the structural differences in their extracellular matrices. Indeed, when the slime mold Dictyostelium transforms itself from a creeping blob of amoebae into a cellularized stalk and fruiting body, its cells secret a cellulosic matrix that begins to resemble the plant cell wall and that imparts some mechanical strength to the ascending stalk. As is the case in the slime mold, the rheology of the cell wall is also crucial to plant form and function, albeit in a more complex way. The wall acts as a cellular exoskeleton that encases plant cells, giving them shape and mechanical stability, gluing them together, restraining their growth, and protecting them from assaults by pathogens and the environment. These and other functions of the wall demand varying properties, and hence the wall’s structure and biochemistry are varied and dynamic (1). In growing plant cells, the wall is strong enough to resist the large mechanical forces generated by the high internal pressure (turgor) typical of plants cells yet still pliant enough to permit enlargement by a form of polymer creep. As plant cells begin to mature, their walls typically become inextensible and resistant to degradation, yet certain cell types and tissues remain capable of wall disassembly and dissolution—in some cases transforming a firm tissue into something with a consistency resembling that of a slime mold.