The Role of Tissue Cell Polarity in Monocot Development

Nature exhibits huge diversity in organ shape, and yet all organs start as small bud-like peripheral outgrowths. Combinations of different spatial and temporal developmental switches in shape determine final organ shape. In plants shape arises through growth, which is defined by axiality and growth rates. Here I tested three hypotheses for how developmental switches in shape could arise: (1) growth rates alone are altered, (2) axiality alone is altered (3) both growth rates and axiality are altered. Using a multidisciplinary approach I explored which of the hypotheses was true for developmental switches in shape during organ development in two monocot models: early grass leaf development and the Hooded barley mutant. Developmental switches in shape were first volumetrically described using 3D imaging. Using this framework, computational models were generated to formulate hypotheses which could account for the switches in shape. Model predictions were then tested using whole-mount immunolocalisation of SISTER OF PINFORMED 1 (SoPIN1), gene expression, and cell division and shape analyses. Synthetic biology was also used to generate a set of transgenic tools for future testing of the models. I found that a developmental switch in shape during early grass leaf development may arise through alterations in growth rates alone (hypothesis 1). In contrast, ectopic flower and wing formation in Hooded may arise through modulation of growth rates and axiality combined (hypothesis 2). In this case a single gene, BKn3, triggers the growth change, possibly through directly influencing tissue cell polarity (if axiality is defined by a polarity based axiality system), with differential effects on shape depending on where it is expressed. This suggests that novel developmental switches in shape could evolve due to single gene mutations, and that during evolution, modulation of growth may have been redeployed in different spatial and temporal patterns to trigger novel changes in shape, ultimately changing final form.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2015

Author dc:creator

• Richardson, Annis

Language dc:language

en