Once we had deposited our baggage and grabbed some lunch, it was time for the afternoon's marathon of talks to start. During this time, the PhD students supported by the Network take centre stage, giving 20-30 minute presentations on their projects. Students funded by a Gatsby scholarship don't just receive a generous sum of money - the programme mentors also provide a comprehensive scheme of training and career development. Hence, each year these students are invited to subject their efforts in the lab to the scrutiny of the Network members. As many of these are world leaders in their field, this is nerve racking to say the least! As my PhD is not funded by Gatsby itself, I ( fortunately!) DIDNT have to give a talk, but as a member of the Network I am allowed to come and cheer on my colleagues and pick up a few ideas for myself!
First we heard from the final year students, who face the daunting task of wrapping up their experiments and settling down to some thesis writing. I was particularly intrigued by Suvi Honkanen's presentation describing the genetic control of rhizoid development in bryophytes ( mosses and liverworts). These species are often described as 'primitive', partly because they lack true roots and instead have weak, thread-like structures called rhizoids. Little is known about how these rhizoids form, so Suvi screened a population on Marchantia polymorpha for mutants with altered rhizoid development. This isn't so time consuming for bryophytes as it is for more 'modern' plants because in these species the dominant life cycle stage is the 'haploid' generation. This only has one set of chromosomes instead of two ( 'diploid' ) and is equivalent to the sperm/ egg cell stage of humans. It also means that, if a gene does have a mutation, it can't be masked by a functional copy on the other chromosome. From this screen, Suvi identified RSL as a critical regulator of rhizoids: when this gene is mutated, the rhizoids fail to form properly. On the other hand over- expression of RSL causes additional 'ectopic' rhizoids to develop on the upper surface of the leaf. Curiously, when the equivalent gene is knocked out in Arabidopsis thaliana - belonging to the utterly different race of 'vascular' plants-the roots don't develop. Thus, RSL is an ancient gene with a conserved mechanism that was already present in the last common ancestor of vascular plants and bryophytes. Another illustration of how the same genes and mechanisms crop up again and again in completely different contexts!
I also enjoyed hearing Stephanie Johnston from Durham University on 'StayGreen Sorghum'. Although we don't eat much of it here, Sorghum is a dietary staple for over 500 million people, and is also important as a livestock feed and a biofuel. Drought resistance varies considerably across sorghum cultivars but StayGreen lines are the champions as their leaves remain green even under severe drought. But no one is entirely sure why, hence Stephanie is currently investigating the potential mechanisms behind this. I must admit a vested interest in this as I worked with Stephanie on this for my undergraduate research project when I was at Durham! She started her search by performing a microarray to identify genes differentially regulated in StayGreen sorghum compared to more drought-susceptible lines. But this identified over 2,000 genes - like looking for a needle in a haystack! Fortunately, many of these genes had been characterised so Stephanie was able to identify common themes and functions. These included genes relating to the control of the stomata - tiny pores onthe underside of leaves that allow water and gas exchange. This suggested that StayGreen Sorghum may retain water by having fewer stomata or by keeping the apertures more tightly closed. It appears that both may be the case. Besides having fewer stomata, StayGreen Sorghum expresses high levels of a gene called SDIR1 ( Salt andDrought Induced Ring Finger 1) . If this is over expressed in Arabidopsis, the stomatal apertures decrease and the plants lose water more slowly. But this comes at a price - smaller pore openings restrict the amount of carbon dioxide the plants can take up for photosynthesis. As a result, StayGreen Sorghum have reduced yields under well-watered conditions. Hence, plant breeders face a challenge in improving stress-tolerance in crops without compromising harvests.
There was also an update from Emma Johnston on the 'explosive transgenic grasses' developed by Liz Dylott's lab at the University of York (see my previous post "Explosive Plant Science" http://scienceasadestiny.blogspot.co.uk/2014/04/explosive-plant-science.html). It's now thought that the genes that allow detoxification of explosives like TNT may also confer resistance to multiple herbicides. If so, these could be a new target for herbicide activity - amazingly, there hasn't been a new mode of herbicide action sincere 1980s. I can't help but feel a little jealous of Emily - this work has just been published in the prestigious journal Science. Most researchers dream of getting at least one paper into Science during their whole career and she has done it before finishing her PhD!
Throwing the floor open to questions can be nerve wracking for the speaker but the feedback and suggestions given by the audience are invaluable. I lost count of the number of times audience members asked " have you ever thought of trying..." Or "why don't you look at...?" The talks also showed how ingenious researchers are when it comes to troubleshooting. Take Jenny Walton, for instance, who worried that growing her Medicago plants in soil was contaminating her trace metal analyses. So she invented her very own hydroponic system using fine mesh and a cat litter tray! It just goes to show the importance of bringing scientists together for encouragement and inspiration - it's not just about free conference dinners!
Thanks to a burst of late-summer sunshine, we were able to congregate in the Fellow's Garden during the refreshment break and admire the flowers. Afterwards, we heard from the second year Gatsby PhD students including Alice Baille, who shares the same office as me at Sheffield. She is investigating whether it is possible to increase photosynthetic efficiency by manipulating the size of air spaces in the spongy mesophyll layer of the leaf. Carbon dioxide uptake can account for up to 50% of the limitations on photosynthetic capacity, hence engineering larger air spaces could boost productivity. One strategy may be to modify the production of pectin, a component of the cell walls which helps to 'glue' cells together. Hence, Alice is currently imaging leaves from plants with mutations in pectinmethylesterase enzymes using fluorescent antibodies to see if this affects wall formation. Will this result in bigger spaces? And - crucially - will this boost photosynthesis? No doubt we will hear more at next year's meeting!
We then jumped from leaf spaces to outer space withour before-dinner speaker, Professor Chris Lintott. Chris is Professor of Astrophysics and Citizen Science in the Department of Physics at Oxford University - although better known as presenter of 'The Sky at Night'. Despite the complete change in topic, his talk was riveting and had us in fits of laughter at times. So much so, that I'm going to make it the subject of a separate blog post- look out for it soon!
After all that science, it's time for tea! Day two coming soon!
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