I genuinely think C4 rice the best shot we've got at alleviating a huge chunk of world hunger in one (extremely difficult) move.
Some key points:
- C4 plants (like maize and sugarcane) are generally about 50% more efficient at biomass accumulation than C3 plants (like rice and wheat). C4 rice could mean a yield increase for rice of up to 50% _with no increase in inputs_
- RuBisCO is by far the most abundant protein in plants. It accounts for the majority of the nitrogen required by C3 plants, and the inefficiency of C3 is the reason we have to use so much nitrogen fertiliser. C4 rice would require considerably less fertiliser than C3 rice.
- C4 plants use CO2 much more efficiently that C3 plants. This allows them to keep their stomata closed much more of the time, so they lose less water through transpiration. This makes C4 plants much more water efficient - C4 rice could require much less water than C3 rice, meaning it could be grown on land that is currently unsuitable for rice production.
- C4 is probably the most interesting example of convergent evolution we know about. It has evolved over 70 times independently. This is quite amazing - it's a complex trait that requires dozens of proteins to be organised in a particular temporal and spatial pattern, and needs a new cell type to be made. Yet it has evolved 70+ times.
- We are using the recurrent evolution pattern as our 'way in' to the problem of figuring out how to control C4 at the molecular level. We analyse gene expression on a massive scale in C4 and C3 sister species from all the evolutionary origins of the trait.
- This involves a lot of interesting software challenges that hn might be interested in. For example, we're working with so many species that we can't sequence all their genomes. But we can sequence their _transcriptomes_, which is all the genes that are expressed at a given time. The sequencing technology produces millions of tiny fragments of the original sequences, which have to be pieced back together to be useful (an NP-hard problem).