7 ms·

What is C4 rice?

72 points by iwwr 12y ago

iwwr 12y ago
Specifically, it's a serious project to adapt the C4 carbon fixation pathway to rice, which is a C3 plant. C4 fixation is much more efficient in drier climates like the ones more prevalent in developing nations. C4 plants while small as a percentage of plant biomass (5%) produce about 30% of carbon fixation among plants.
- gus_massa 12y ago
  More details about C4 from Wikipedia: http://en.wikipedia.org/wiki/C4_carbon_fixation http://en.wikipedia.org/wiki/C4_carbon_fixation > About 7,600 plant species use C4 carbon fixation, which represents about 3% of all terrestrial species of plants. > These include the food crops maize, sugar cane, millet, and sorghum (The section http://en.wikipedia.org/wiki/C4_carbon_fixation#C4_leaf_anatomy http://en.wikipedia.org/wiki/C4_carbon_fixation#C4_leaf_anat... is easier to read because it's not so technical.) Is it easier to transform the rice in a C4 plant or to transfprm the rice fields to maize fields? [Disclaimer: My family is from the north of Argentina and we really like maize.]
  - PaulHoule 12y ago
    Maize is fine but some people like rice and a big yield increase would help feed them.
  - ufo 12y ago
    As a Brazilian, replacing rice+beans with something else sounds unthinkable. I imagine asians who eat rice everyday would say something similar.
  - Blahah 12y ago
    Most of asia uses rice as a staple, and it has a cultural history going back over 2000 years. Many governments and other groups have tried to explore encouraging dietary change away from rice as a staple, but it has so far not made any difference. A 50% yield increase in rice could alleviate starvation for the most starving continent on the planet.
  - hga 12y ago
    I suppose it's not entirely an accident that in my part of the Midwest, SW Missouri, and I gather a lot of it, maize and sorghum (around here called "milo") are the two most popular things to plant (the milo is fed to animals). My mother, however, grew up on a rice farm in Louisiana. C4 rice would be very welcome as long as there's plenty of hungry mouths to feed. As far as the biology goes, not that I'm paying any attention to the field, this is the most ambitious genetic engineering project I've ever heard of. Hope they can pull it off.
  - logn 12y ago
    And I wonder about quinoa too, which is a complete protein, grows well in dry climates, and is also C4. And quinoa could probably substitute for rice in many recipes. The price is slightly high right now, but that's because supply has not kept with demand (due in part to the fact that it's gluten free).
- afarrell 12y ago
  I wonder how hard it would be to do this in ocean algae and phytoplankton and it that could fight global warming.
  - iwwr 12y ago
    The pathway crosses several cells, one in which CO2 is filtered from an oxygen atmosphere and another anoxic stage where the CO2 is fixed again, this time to produce sugars which plants actually need. The two stage fixation prevents something called 'photorespiration' where existing oxygen can 'steal' some of the rubisco mollecules which would otherwise associate with CO2. So this is a multicellular process and could not be adapted to algae.
  - Blahah 12y ago
    Many algae already use a carbon concentrating mechanism [0] similar to C4. It works in a similar way, by concentrating CO2 around RuBisCO, the key enzyme that creates sugar from CO2. In C4 plants, the RuBisCO is kept in a wax-enclosed cell, and the CO2 is pumped in. In algae, which are single-celled, the RuBisCO aggregates together into a bubble-like structure called a pyrenoid [1], and a high CO2 concentration is maintained inside. 0: http://en.wikipedia.org/wiki/Photosynthesis#Carbon_concentrating_mechanisms http://en.wikipedia.org/wiki/Photosynthesis#Carbon_concentra... 1: http://en.wikipedia.org/wiki/Pyrenoid http://en.wikipedia.org/wiki/Pyrenoid
- mapt 12y ago
  How might it compare to http://en.wikipedia.org/wiki/Upland_rice http://en.wikipedia.org/wiki/Upland_rice ?
  - Blahah 12y ago
    Upland rice was bred using natural variation within rice populations. C4 rice will require much more complex targeted genetic design. However, we are also harnessing natural variation, and are doing massive-scale screens of natural cultivars. The idea is that we want to do the engineering the in the most C4-like rice that exists.
biggot_man 12y ago
It looks like Bill Gates also enjoys eating sh*t (besides drinking it).
Blahah 12y ago
PhD student working on the C4 rice project here. On the road right now but happy to answer questions when I can find a moment. 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).
- seanp2k2 12y ago
  What is the plan to deal with the backlash from uneducated people screaming about how bad GMO is?
  - JoshTriplett 12y ago
    A combination of education and (mostly) ignoring them, I would hope. Such screaming comes from people who expect to have food available for their next meal, and tends to evaporate when hungry.
meepmorp 12y ago
I wonder how this will fare against the tide of anti-GMO silliness that seems to be prevalent these days. Even something unquestionably useful like golden rice has been met with fear mongering and paranoia.
- Moru 12y ago
  I don't want to play the devils advocate but I was just watching "I, robot" on TV... What ever could go wrong playing with nature? :-)
  - TeMPOraL 12y ago
    Everything humans do is "playing with nature". Technology only gives us new ways to "play".
  - meepmorp 12y ago
    > What ever could go wrong playing with nature? :-) No offense (seriously), but this argument is the biggest load of bullshit. Do you think there are any major food sources that just developed, as is, naturally? Pretty much every vegetable, fruit, grain, or pulse - has been selectively developed by humans, many over the course of thousands of years. The bananas we eat can't even reproduce without our direct intervention. Animals, too, both livestock and pets - that dachshund wasn't running wild in the forest before we tamed it. We've been playing with nature as long as we've been able to do so. Genetic engineering is just a better set of tools for it. Somehow, though, people have convinced themselves that the selective breeding process is safer than direct genetic manipulation. Because, of course, breeding crops based on taste or visual appeal makes for safer and better development of crops - why pick the specific traits you want when you can just fumble about for generations without a clear idea of what you're gonna get? Should we be careful? Sure, in this as in all things we do; but the fact that the technology is new isn't the reason why.
  - IndianAstronaut 12y ago
    Bevers build dams which divert the flow of water, sometimes drastically. Are they playing with nature?
jqm 12y ago
I've always wondered if it would be possible to incorporate carbon fixation schemes similar to those used by cactus into food plants (Grains might be difficult, but maybe different types of fruit and vegetables, citrus, which I understand is distantly related to cactus, for instance?). Sure, growth rates would be slow, but the lack of need for irrigation and ability to utilize tracts of arid land might offset this. I'm sure somebody at some point has looked into this. Any insight OP?
- Blahah 12y ago
  Fly-by comment: C4 is very similar to CAM, the scheme that cacti use. So the C4 rice project is essentially what you're thinking of, except that the reactions are separated spatially in C4 instead of temporally in CAM.
ciconia 12y ago
The background section does not mention the fact that a substantial part of crops is used to feed animals in the meat/dairy industry, which is then consumed mostly in developed countries. Another part of agricultural production is used for manufacturing bio-diesel (1). In light of this, it should be questioned whether the use of optimized crop variants could be the right answer to the problem of feeding billions of people, and whether it can be a _sustainable_ solution. OK, let's say we can increase yield by 50%. What comes after that? (2) I know it is a controversial and touchy subject, and also somewhat off-topic, but personally I'm quite convinced that the answer to current food shortages is not increased production, but rather the reduction of (over)consumption. [1] The UNEP reports that "today, nearly half of the world’s cereals are being used for animal feed." - http://www.unep.org/pdf/FoodCrisis_lores.pdf http://www.unep.org/pdf/FoodCrisis_lores.pdf [2] It is interesting that the same UNEP report, among the seven options it proposes for dealing with food shortage (pp. 92-93), does not once mention GM crops or increasing yields as a possible solution.
- Blahah 12y ago
  You're absolutely right in the first part - a huge proportion of arable land is used to feed animals. However, this doesn't change the optimal strategy for feeding people in the medium term, for a bunch of reasons: 1. The arable land used for feeding animals would not necessarily be available for feeding people who are hungry now if it were to be freed up. 2. In general the world's poorest people grow their own food on small plots of land and don't produce a lot of meat. They care about the productivity of their plot of land. 3. Changing the world's eating habits is a gargantuan task. Are you suggesting we stop trying to feed people in the medium term using technology, and allow them to starve while we try to convince westerners not to eat meat? I know this is not what you're suggesting - but it serves to show that we should of course be pursuing all the available routes to alleviating hunger. > OK, let's say we can increase yield by 50%. What comes after that? That's enough to meet the entire calorific intake increase for rice-eating countries by the time population stabilises. By around 2050 the world population will have stopped growing. So what comes after that is that everyone is fed, and we can enjoy a world where very few people go hungry while we fix the much more difficult problems of economics and society. Finally, the UNEP report doesn't talk about the potential for GM crops because it's out of scope - the report is about environmental factors in food production. They do say that their projections could be affected by improvements in GM technology.

72 points by iwwr 12y ago

iwwr 12y ago

Specifically, it's a serious project to adapt the C4 carbon fixation pathway to rice, which is a C3 plant. C4 fixation is much more efficient in drier climates like the ones more prevalent in developing nations. C4 plants while small as a percentage of plant biomass (5%) produce about 30% of carbon fixation among plants.

gus_massa 12y ago
More details about C4 from Wikipedia: http://en.wikipedia.org/wiki/C4_carbon_fixation http://en.wikipedia.org/wiki/C4_carbon_fixation > About 7,600 plant species use C4 carbon fixation, which represents about 3% of all terrestrial species of plants. > These include the food crops maize, sugar cane, millet, and sorghum (The section http://en.wikipedia.org/wiki/C4_carbon_fixation#C4_leaf_anatomy http://en.wikipedia.org/wiki/C4_carbon_fixation#C4_leaf_anat... is easier to read because it's not so technical.) Is it easier to transform the rice in a C4 plant or to transfprm the rice fields to maize fields? [Disclaimer: My family is from the north of Argentina and we really like maize.]
- PaulHoule 12y ago
  Maize is fine but some people like rice and a big yield increase would help feed them.
- ufo 12y ago
  As a Brazilian, replacing rice+beans with something else sounds unthinkable. I imagine asians who eat rice everyday would say something similar.
- Blahah 12y ago
  Most of asia uses rice as a staple, and it has a cultural history going back over 2000 years. Many governments and other groups have tried to explore encouraging dietary change away from rice as a staple, but it has so far not made any difference. A 50% yield increase in rice could alleviate starvation for the most starving continent on the planet.
- hga 12y ago
  I suppose it's not entirely an accident that in my part of the Midwest, SW Missouri, and I gather a lot of it, maize and sorghum (around here called "milo") are the two most popular things to plant (the milo is fed to animals). My mother, however, grew up on a rice farm in Louisiana. C4 rice would be very welcome as long as there's plenty of hungry mouths to feed. As far as the biology goes, not that I'm paying any attention to the field, this is the most ambitious genetic engineering project I've ever heard of. Hope they can pull it off.
- logn 12y ago
  And I wonder about quinoa too, which is a complete protein, grows well in dry climates, and is also C4. And quinoa could probably substitute for rice in many recipes. The price is slightly high right now, but that's because supply has not kept with demand (due in part to the fact that it's gluten free).
afarrell 12y ago
I wonder how hard it would be to do this in ocean algae and phytoplankton and it that could fight global warming.
- iwwr 12y ago
  The pathway crosses several cells, one in which CO2 is filtered from an oxygen atmosphere and another anoxic stage where the CO2 is fixed again, this time to produce sugars which plants actually need. The two stage fixation prevents something called 'photorespiration' where existing oxygen can 'steal' some of the rubisco mollecules which would otherwise associate with CO2. So this is a multicellular process and could not be adapted to algae.
- Blahah 12y ago
  Many algae already use a carbon concentrating mechanism [0] similar to C4. It works in a similar way, by concentrating CO2 around RuBisCO, the key enzyme that creates sugar from CO2. In C4 plants, the RuBisCO is kept in a wax-enclosed cell, and the CO2 is pumped in. In algae, which are single-celled, the RuBisCO aggregates together into a bubble-like structure called a pyrenoid [1], and a high CO2 concentration is maintained inside. 0: http://en.wikipedia.org/wiki/Photosynthesis#Carbon_concentrating_mechanisms http://en.wikipedia.org/wiki/Photosynthesis#Carbon_concentra... 1: http://en.wikipedia.org/wiki/Pyrenoid http://en.wikipedia.org/wiki/Pyrenoid
mapt 12y ago
How might it compare to http://en.wikipedia.org/wiki/Upland_rice http://en.wikipedia.org/wiki/Upland_rice ?
- Blahah 12y ago
  Upland rice was bred using natural variation within rice populations. C4 rice will require much more complex targeted genetic design. However, we are also harnessing natural variation, and are doing massive-scale screens of natural cultivars. The idea is that we want to do the engineering the in the most C4-like rice that exists.

biggot_man 12y ago

It looks like Bill Gates also enjoys eating sh*t (besides drinking it).

Blahah 12y ago

PhD student working on the C4 rice project here. On the road right now but happy to answer questions when I can find a moment. 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).

seanp2k2 12y ago
What is the plan to deal with the backlash from uneducated people screaming about how bad GMO is?
- JoshTriplett 12y ago
  A combination of education and (mostly) ignoring them, I would hope. Such screaming comes from people who expect to have food available for their next meal, and tends to evaporate when hungry.

meepmorp 12y ago

I wonder how this will fare against the tide of anti-GMO silliness that seems to be prevalent these days. Even something unquestionably useful like golden rice has been met with fear mongering and paranoia.

Moru 12y ago
I don't want to play the devils advocate but I was just watching "I, robot" on TV... What ever could go wrong playing with nature? :-)
- TeMPOraL 12y ago
  Everything humans do is "playing with nature". Technology only gives us new ways to "play".
- meepmorp 12y ago
  > What ever could go wrong playing with nature? :-) No offense (seriously), but this argument is the biggest load of bullshit. Do you think there are any major food sources that just developed, as is, naturally? Pretty much every vegetable, fruit, grain, or pulse - has been selectively developed by humans, many over the course of thousands of years. The bananas we eat can't even reproduce without our direct intervention. Animals, too, both livestock and pets - that dachshund wasn't running wild in the forest before we tamed it. We've been playing with nature as long as we've been able to do so. Genetic engineering is just a better set of tools for it. Somehow, though, people have convinced themselves that the selective breeding process is safer than direct genetic manipulation. Because, of course, breeding crops based on taste or visual appeal makes for safer and better development of crops - why pick the specific traits you want when you can just fumble about for generations without a clear idea of what you're gonna get? Should we be careful? Sure, in this as in all things we do; but the fact that the technology is new isn't the reason why.
- IndianAstronaut 12y ago
  Bevers build dams which divert the flow of water, sometimes drastically. Are they playing with nature?

jqm 12y ago

I've always wondered if it would be possible to incorporate carbon fixation schemes similar to those used by cactus into food plants (Grains might be difficult, but maybe different types of fruit and vegetables, citrus, which I understand is distantly related to cactus, for instance?). Sure, growth rates would be slow, but the lack of need for irrigation and ability to utilize tracts of arid land might offset this. I'm sure somebody at some point has looked into this. Any insight OP?

Blahah 12y ago
Fly-by comment: C4 is very similar to CAM, the scheme that cacti use. So the C4 rice project is essentially what you're thinking of, except that the reactions are separated spatially in C4 instead of temporally in CAM.

ciconia 12y ago

The background section does not mention the fact that a substantial part of crops is used to feed animals in the meat/dairy industry, which is then consumed mostly in developed countries. Another part of agricultural production is used for manufacturing bio-diesel (1). In light of this, it should be questioned whether the use of optimized crop variants could be the right answer to the problem of feeding billions of people, and whether it can be a _sustainable_ solution. OK, let's say we can increase yield by 50%. What comes after that? (2) I know it is a controversial and touchy subject, and also somewhat off-topic, but personally I'm quite convinced that the answer to current food shortages is not increased production, but rather the reduction of (over)consumption. [1] The UNEP reports that "today, nearly half of the world’s cereals are being used for animal feed." - http://www.unep.org/pdf/FoodCrisis_lores.pdf http://www.unep.org/pdf/FoodCrisis_lores.pdf [2] It is interesting that the same UNEP report, among the seven options it proposes for dealing with food shortage (pp. 92-93), does not once mention GM crops or increasing yields as a possible solution.

Blahah 12y ago
You're absolutely right in the first part - a huge proportion of arable land is used to feed animals. However, this doesn't change the optimal strategy for feeding people in the medium term, for a bunch of reasons: 1. The arable land used for feeding animals would not necessarily be available for feeding people who are hungry now if it were to be freed up. 2. In general the world's poorest people grow their own food on small plots of land and don't produce a lot of meat. They care about the productivity of their plot of land. 3. Changing the world's eating habits is a gargantuan task. Are you suggesting we stop trying to feed people in the medium term using technology, and allow them to starve while we try to convince westerners not to eat meat? I know this is not what you're suggesting - but it serves to show that we should of course be pursuing all the available routes to alleviating hunger. > OK, let's say we can increase yield by 50%. What comes after that? That's enough to meet the entire calorific intake increase for rice-eating countries by the time population stabilises. By around 2050 the world population will have stopped growing. So what comes after that is that everyone is fed, and we can enjoy a world where very few people go hungry while we fix the much more difficult problems of economics and society. Finally, the UNEP report doesn't talk about the potential for GM crops because it's out of scope - the report is about environmental factors in food production. They do say that their projections could be affected by improvements in GM technology.