X-rays and Barley Mutants!

Blog readers may be familiar with the botanical terms monocots and dicots. Dicots include many woody species, and monocots include important cereal crops such as wheat and barley (i.e. grasses). These are basics of plant biology that I teach my students in environmental archaeology. Monocots such as cereals of course are central in archaeological research around the origins of agriculture and domestication, whilst dicots feature in studies of ancient fuel use. 

One of the major differences between monocots and dicots is the organisation of the stem. Dicot stems, or cambium, have radial growth, that forms the distinct rings that we use for dendrochronology. This growth is controlled by the interaction of two proteins, TDIF and PXY. Monocots do not have a cambium, but they do have the genes for TDIF and PXY. What then, is the function of these genes in monocots, if not to produce cambium? This question is the basis of a major BBSRC funded project I've been involved in for the past year "Modified function of a stem cell regulator in monocots and dicots" (Barley PXY for short), led by PI Dr Peter Etchells in Durham Biosciences. 

There are several reasons why archaeologists are very interested in plant genetics, but in this case, my interest is due to the focus on changes in plant cellular morphology. I've had a long standing interest in how phytoliths are interpreted in archaeology. There is very little in the literature on how phytolith morphology relates to the organic plant tissue prior to the plant decaying and entering the archaeological record. Furthermore, how variations in the organic tissue as the plant grows could impact the phytolith morphology. This is of crucial importance for several key questions in archaeology. Phytolith morphology is used to distinguish wild versus domestic plants for example, and the size of cereal husk phytoliths has been used to infer ancient water availability and irrigation. 

In Barley PXY, the Durham Biosciences team are creating mutants by turning the TDIF and PXY genes on and off, and observing what happens to the cells in the plant stems. In the NEMCAS lab in archaeology, we are developing a method to image the mutant cellular structure in three dimensions, using XR-CT (micro computed tomography). I am becoming a little obsessed with XR-CT. The idea that we can look inside an organism in 3D at the cellular level, I just find that incredible. Barley PXY is answering some fundamental questions in plant evolutionary biology, and at the same time it is raising questions about how we interpret phytoliths and other microparticles in archaeology. The next step is to explore how we can use XR-CT to help develop better understanding of phytolith formation, how phytoliths relate to the original plant morphology, and how consistent that morphology really is. I would be really keen to supervise any PhD or postdoc projects exploring these questions!

Here is a picture of the BBSRC team, Dr Agnieszka Gladala-Kostarz and Dr Riley Snyder, at the recent Genetics Society Seed Plant Meeting in Durham, where we presented our preliminary results. I can't wait to get this published and share some of the amazing CT reconstructions Riley has worked on!