BBSRC SWBio DTP studentship available

Roles for polarity in Marchantia thallus shape determination

Supervisors: Dr Jill Harrison (Bristol) and Dr Martin Homer (Bristol)

Background:

Plant shapes range from tiny string or mat-like forms to massive multilayered upright forms with complex organ systems such as shoots, roots and leaves. Despite these wide differences in shape, many plant gene families are very ancient, predating diversification. We can therefore study the mechanisms for shape determination in simple plants such as liverworts and use the knowledge gained to understand plant shape determination in general.

To this end, my lab has used a combination of live imaging, statistical model fitting, computational modelling and molecular biology to discover mechanisms regulating shape in the liverwort Marchantia polymorpha (Solly et al. (2017): Current Biology).

We found that Marchantia undergoes a stereotypical sequence of shape transitions during development. Key aspects of global plant shape depend on regional growth rate differences specified by the co-ordinated activities of the growing apical notches. Computational modelling showed that a diffusible, growth-promoting cue produced in the notches is likely to pattern regional growth rate differences, and pharmacological experiments suggested that the plant hormone auxin may equate to the model growth-promoting cue.

New models suggest a role for differential oriented growth (anisotropy) in Marchantia shape determination. Anisotropy emerges as an outcome of underlying tissue polarities, and directional auxin transport is one potential mechanism for generating polarity.

 

Your project will build on the prior work above to determine how auxin contributes to plant shape determination in Marchantia.

It will:

1. Predict the effects of different tissue polarities on Marchantia shape by modelling

2. Analyse the auxin distribution in Marchantia in comparison to distributions predicted from modelling

3. Disrupt auxin biosynthesis, directional transport, conjugation and decay and test the effect on growth and shape

4. Use live-imaging, image segmentation and quantitative growth analyses to discover how growth and shape change in plants with different auxin biology.

Training:

By combining computational and wet lab approaches, the project will provide training at the cutting edge of the plant evolution and development fields. The techniques that you learn will be broadly applicable in the academic biology and biotech sectors. The skills that you learn will be widely transferable to other areas such as science policy, publishing and computing.

Reading:

Solly et al (2017).  Regional growth rate differences specified by apical notch activities regulate liverwort thallus shape.  Current Biology 27: 16-26.

Applications:

Applications will be open on the SWBio DTP website  and the closing date is the 3^rd December. Informal enquiries to Dr JillHarrison.

BBSRC SWBio CASE DTP studentship available

Intercepting CLAVATA receptor-like kinase function to engineer ear size in wheat

Supervisors: Dr Jill Harrison (Bristol), Professor Keith Edwards (Bristol) and Dr Chris Burt (RAGT Seeds)

Ensuring continuous global food security will be a major challenge of the 21st century, and wheat contributes approximately 20% of the total calories consumed by humans (FAO, 2017). In cereals like wheat, inflorescence (ear) size determines the number of flowers (florets) and grains produced, and this aspect of plant architecture is regulated by the activity of stem cells in the growing shoot tips. The CLAVATA peptide/ receptor-like kinase signalling pathway maintains the size of the stem cell pool during plant development, and mutants in maize and tomato have increased yields, arising due to an increase in size of the stem cell pool. This project aims to intercept wheat CLAVATA

signalling to engineer ears with more fertile grain sites and increase yield.

The project will involve:

(1) Identification of wheat CLAVATA pathway components

(2) Expression analyses of wheat CLAVATA pathway components

(3) Generation phenotypic analysis of wheat CLAVATA pathway mutants.

Expertise:

Dr Harrison’s group has recently published gene trees for CLAVATA pathway components from a range of land plants (Whitewoods et al. (2018)), and she has experience of analysing gene expression patterns and function in a wide range of plant species. Professor Edwards and colleagues from the Bristol Centre for Agricultural Innovation have extensive experience with wheat having sequenced the genome (Brenchley et al. (2012)), identified many mutants from the exome sequenced Cadenza TILLING mutant population (Krasileva et al. (2017)) and established engineering procedures using CRISPR/Cas9. The CASE partnership with RAGT seeds will bring an opportunity for the student to directly experience wheat breeding and exchange knowledges and finding with wheat growers.

By combining computational and wet lab approaches, your project work will provide training at the cutting edge of the plant development field. You will benefit from further formal teaching and internships included in the SWBioDTP programme. The skills and techniques you learn will be broadly applicable in the academic biology and biotech sectors and widely transferable amongst areas such as science policy, publishing and computing.

Reading:

Brenchley et al. (2012). Analysis of the bread wheat genome using whole-genome shotgun sequencing. Nature 491: 705-710. Food and Agriculture Organization of the United Nations, FAOSTAT statistics database, Food balance sheets (2017); www.fao.org/faostat/en/#data/FBS.

Krasileva et al. (2017). Uncovering hidden variation in polyploid wheat. PNAS 114: E913-E921.

Whitewoods et al. 2018. CLAVATA was a genetic novelty for the morphological innovation of 3D growth in land plants. Current Biology 28: 2365-2376.

Applications:

Applications will be open on the SWBio DTP website  and the closing date is the 3^rd December. Informal enquiries to Dr JillHarrison.