Food security challenges - from bugs to beating climate change

Here’s my round up of a recent departmental seminar where Professor Tammy Sage introduced us to a little-known but highly important threat to food security and how plant science is being used to overcome it. Plus I investigate one of the rapidly upcoming food ‘sustainability trends’ – eating insects for dinner!

Climate change is a worrying enough prospect as it is, but imagine if you were a species that simply couldn’t reproduce above a certain temperature? This seems to be the situation with many plants, which worryingly include key staples. Rice, wheat and corn are particularly temperature sensitive during the process of meiosis and mitosis resulting in failed production of the male gametes (sex cells). In many species the pollen aborts upon exposure to temperatures ≥ 30°C: a phenomenon which is already starting to occur in some of the major rice, corn and wheat growing regions.

So what can be done about this ticking time-bomb for food security? Professor Tammy Sage (University of Toronto, California) and her lab group are working on the problem by identifying plant genes that confer high-temperature resilience during pollen development. This would be very difficult to do in rice: although it has the smallest genome of the major cereal crops, it is still around 430 million base pairs and 12 pairs of chromosomes. So, like me, Tammy uses Arabidopsis thaliana, the model organism of the plant science world which has a fully sequenced genome of only 135 million base pairs and 5 chromosome pairs. This makes is much quicker to identify gene sequences related to thermotolerance that can be used to develop markers to search for these in crops.

Pollen grains germinating on the stigma of the model grass, Brachypodium. 

Photo credit: Professor Tammy Sage.

Tammy began by comparing Arabidopsis accessions with high and low seed production when exposed to 33°C. Through this process, a gene was identified (called HTT for High Temperature Tolerance) that was highly expressed in a pollen-specific fashion to a greater degree in the thermotolerant cultivar. But how exactly does it work? Tammy’s research has shown that HTT has a role in preventing dangerous molecules called reactive carbonyl species (RCS) from accumulating in pollen grains. Like reactive oxygen species (ROS), RCS can function as signalling molecules at low temperatures but excessive amounts (which can be caused by high temperatures) can be damaging. RCS have a much longer half-life than ROS and can also cross membranes, allowing them to reach DNA in the nucleus. In humans, RCS contribute to diseases such as Parkinson’s, diabetes, arthritis and Alzheimer’s.

In plants, HTT is expressed during the later stages of pollen development and Arabidopsis mutants with an inactive version of the gene produce nonviable pollen grains. So how exactly does HTT protect against the damage caused by RCS? It is still unclear but Tammy’s research indicates that HTT protects the enzymes involved in plastidic glycolysis from becoming carbonylated. Plastidic glycolysis liberates energy from starch in small organelles in the plant cells. This is needed to fuel the growth of the pollen tube once it lands on the female stigma. As well, HTT prevents carbonylation of signalling proteins that activate the heat transduction pathway. These act like an alarm system for high temperatures and turn on a range of responses that increase thermotolerance, including altering the fluidity of cell membranes and removing damaged proteins.

After all these years of study, it’s now time to turn these insights into action. Tammy is now working on introducing these genes into rice and also Camelina sativa (used to make jet fuel). Curiously, HTT1 is NOT naturally expressed in rice pollen, which may explain why it is so temperature sensitive. Hopefully, introducing HTT could act as a ‘protective sunscreen’ that will allow our crops to keep reproducing in our warming world.

Tasty? Bugs for dinner...

As for me, I recently attended a seminar called “Would you eat bugs?” as part of the Sheffield Festival of Debate, organised by the Grantham Centre for Sustainable Futures. As insect farming requires only a fraction of the land and water resources used for other animals, this could be a real viable option for a more sustainable protein source. But this would require overcoming several hurdles including the Western ‘Yuck! Factor’, the high temperatures (and thus energy costs) that many species require and allengenicity issues. Perhaps the most promising way forward is insect-fortified flours that can be made into pasta or cereal bars. At the event, we were able to sample Yumpa Bars, high-energy and protein bars made using cricket flour, besides mixes containing whole bugs. Whilst I particularly enjoyed the spicy crickets, I’m not convinced that insects will be going mainstream in the UK soon. More likely, they will be a bigger part of the solution in countries which already have the infrastructure, climate and cultural attitudes in place to facilitate their adoption. But for something different, it’s certainly worth a try!

And with that, I had better hop off to my plants…. Thanks for reading!