Morphogenesis Control By Mechanical Stress

Khadka, Jason

Mechanism behind efficient plant growth

dc.contributor.advisor	Alim, Karen Dr.
dc.contributor.author	Khadka, Jason
dc.date.accessioned	2019-08-29T08:58:53Z
dc.date.available	2019-08-29T08:58:53Z
dc.date.issued	2019-08-29
dc.identifier.uri	http://hdl.handle.net/21.11130/00-1735-0000-0003-C1A5-8
dc.identifier.uri	http://dx.doi.org/10.53846/goediss-7606
dc.language.iso	eng	de
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc	571.4	de
dc.title	Morphogenesis Control By Mechanical Stress	de
dc.title.alternative	Mechanism behind efficient plant growth	de
dc.type	doctoralThesis	de
dc.contributor.referee	Alim, Karen Dr.
dc.date.examination	2019-05-29
dc.description.abstracteng	Morphogenesis of plants and animals often emerges from mechanical moulding and deformations. Yet, how precisely cells as individual mechanical entities can act to shape a tissue reliably and ef- ficiently is still puzzling. In plants, the mechanics of cells within a tissue is particularly well de- fined as individual cell growth is essentially mechanical yielding of cell wall in response to internal turgor pressure. Most intriguingly, cell wall stiffness is controlled by biological signalling and is observed to respond to mechanical stresses building up within a tissue. What is the role of such a mechanical feedback during morphing in three dimensions? Here, we propose a three dimensional vertex model to investigate the mechanics in plants tissues. We employ the model to examine the onset of organogenesis at the shoot tip and the polarised growth of plant tissue that leads to the elongated shoot. To investigate the mechanism of organ growth from the shoot apical meristem, a tissue at the tip of the plants, we simulate the bulging of young organs, called the primordia, on the surface of the tissue. We find that the primordia are initiated and their growth primarily governed by the ratio of growth rates of faster growing primordial cells to slower growing meristem cells surrounding them. By introducing the remodelling of cell walls with stresses through mechanical feedback, we observe, remarkably, that the outgrowth of the primordia is more efficient when the feedback is allowed to modify the cellular growth. Our quantitative analysis of simulation data shows that the feedback acts by not only modulating cell growth, by reorganising the walls, but also by chang- ing the stress pattern within the tissue. The twofold mechanism by which feedback acts allows the self-amplification and propagation of growth and stress anisotropies on the tissue. We observe that it significantly alters the mechanical properties of boundary cells around the growing primordia. These cells face increased anisotropic stresses and are restricted from growing. With our study, we see that this restructuring of tissue mechanics forms a stiff ring-like boundary around the primor- dia, which effectively squeezes out the organ. The experimental observations reported in literature on the growing plant tissues corroborate our findings. Thus, we show that the mechanical feedback on cellular growth enables plants to grow organs efficiently out of the meristem by reorganising the cellular growth rather than increasing the growth rates of primordial cells further. The elongated body of plant is vital in positioning the growing organs to gather resources better. In the second part of the work, we investigate the transformation of the hemispherical apical sur- face of plant into the tall cylindrical body by simulating the elongation of the plant tissue. Through the various arrangements of growth on the tissue, we analyse the efficiency of mechanical develop- ment of plants in lengthening the shoot. We find that the confined growth on the peripheral regions as observed in the meristem of plants is the most efficient to generate elongation. The elongation from the peripheral growth is the highest regardless of the mechanical feedback and the applica- tion of cell division. With this, we deduce that the plants are adept at generating cylindrical body and optimally placing the organs. In conclusion, we show that the three-dimensional mechanical modelling is a dependable method for exploring plant morphogenesis. We prove that plant cells read from the tissue-wide mechan- ical patterns to organise their growth and that the mechanical feedback guides efficient initiation of organs from the apical surface. With the analysis of spatial arrangement of growth, we also con- firm that the growth pattern in the meristem is optimised to enhance the development of elongated body of plants.	de
dc.contributor.coReferee	Klumpp, Stefan Prof. Dr.
dc.subject.eng	Tissue Mechanics	de
dc.subject.eng	Morphogenesis	de
dc.subject.eng	Plant Tissue Growth	de
dc.subject.eng	Vertex Model	de
dc.subject.eng	Three dimensional tissue model	de
dc.identifier.urn	urn:nbn:de:gbv:7-21.11130/00-1735-0000-0003-C1A5-8-4
dc.affiliation.institute	Göttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften (GGNB)	de
dc.subject.gokfull	Biologie (PPN619462639)	de
dc.identifier.ppn	167280213X

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Das Dokument erscheint in:

GGNB - Göttinger Graduiertenzentrum für Neurowissenschaften, Biophysik und molekulare Biowissenschaften [1115]
GGNB - Göttingen Graduate Center for Neurosciences, Biophysics and Molecular Biosciences

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