Comparative Cell Morphology using Tip Growing Cells
Tip growing cells are walled cells exhibiting turgor driven apical growth, that include examples such as the pollen tubes and hyphae. They exhibit an apical region of cell growth that creates a mechanically soft spot at the apex of the cell 'tip' and rigid at the cylindrical portion. Many different species across the tree of life have convergently evolved tip growth as a means to explore their environments through growth. This includes species within the Plants, Fungi and Protists such as Oomycetes.
Apical shapes of tip growing cells vary from round to tapered. The shape of tip growing cells is determined by how the cell wall extensibility spatially transitions from the region of apical softness to the the rigid wall of the cylindrical body. My mentor, Dr. Enrique Rojas at NYU, was able to describe the full range of morphologies for tip growing cells using a viscoelastic model that decays the apical extensibility over two distinct length scales.
I experimentally validated the existence of a mechanical instability predicted in the space of apical tip growing cell morphologies that separates fast growing thin morphologies from slow growing wider morphologies. I used Achlya bisexualis which had a tapered morphology close to the predicted mechanical instability. We discovered that the dependence of cell shape on cell elongation indicates a fitness landscape, whereby all naturally occurring cell shapes only occupy the region of the morphological space that corresponds to fast elongating, thin morphologies.
Growing Hypha of Achlya bisexualis
1. Wide,Slow growing
2. Thin,Fast growing
Dynamics of Pressurized Flow in Hyphal Networks
Hyphae behave as inflated pipes carrying cytoplasm and organelles. There is inherent flow of material towards the growing tip and hence hyphae can be viewed as pressurized pipes with a flow of cytoplasm and material. Interestingly, these 'pipes' are connected to each other in contiguous cytoplasmic networks, as they are no absolute separations. It is not clear how pressurized flow is distributed between connected hyphae.
In my research, I aim to study how flow may be distributed in the simple coenocytic mycelium of Achlya bisexualis. I employ hyperosmotic shocks to rapidly decrease the turgor pressure and investigate how pressure may be redistributed. So far, I have observed that hyperosmotic shock causes a differential response between adjacent hyphae, implying complex pressure redistribution between connected hyphae. I plan to study this phenomenon further
Young mycelium of Achlya bisexualis