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Better hemoglobins for legumes

Fix that N!
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Bioavailable nitrogen is a limiting factor for agriculture. Because of this, lots of petrochemicals are used to augment the soil and allow crops to grow. Another way to do this is with legumes - these crops have the ability to fix nitrogen by virtue of symbiotic bacteria residing in special root organs. Rotating a legume crop (for example alfalfa) into a field will improve the nitrogen in the soil.

The rhizobium bacteria that fix nitrogen do so with some complicated chemistry. The chemical apparatus responsible is easily poisoned by oxygen - a delicate thing, given that these bacteria reside in a plant which requires oxygen for metabolism. The rhizobia protect themselves using hemoglobin. Within the root nodules (which are red by virtue of hemoglobin), the legume hemoglobin (or leghemoglobin) scavenges oxygen and protects the nitrogen fixing chemistry.

Could nitrogen fixing ability be improved by better oxygen scavenging? Certain worms have hemoglobin which is even more oxygen avid than leghemoglobin. I propose a simple genetic engineering experiment: engineer rhizobia to express high affinity worm hemoglobin. If it protects nitrogen fixation better, one would expect to see improved legume growth. Which would be good on many fronts.

bungston, Apr 11 2008

Different hemoglobins with oxygen affinities. http://www.scienced...415ce41796d5bc98a2a
[bungston, Apr 11 2008]

Wikipedia on leghemoglobin http://en.wikipedia.../wiki/Leghemoglobin
[bungston, Apr 11 2008]

Idea that inspired this. plankton_20with_20n...oceanic_20abundance
[bungston, Apr 11 2008]

[link]






       It would be theoretically possible to decrease the overall oxygen content of the atmosphere by binding the oxygen with, for instance, carbon or hydrogen. An approach involving the oxidation of carbon-based strata would have two benefits; oxygen would be captured, and the extra CO2 in the atmosphere would promote the growth of green plants.   

       This would, however, be a massive undertaking, involving the vigorous involvement and cooperation of a large proportion of the population of your planet, so it probably couldn't be implemented in any meaningful way. And it would take centuries of effort before it started to pay off - since your species is notoriously short-term in their outlook, this idea is definitely halfbaked.
8th of 7, Apr 11 2008
  

       It's an interesting question. Are legumes limited by their ability to sequester oxygen? I would have guessed not (in that haemoglobins are quite plastic in evolutionary terms, so you'd have expected the legumes to have done this for themselves). On the other hand, most plants have failed to evolve root nodules, so the utility argument is a bit weak.
MaxwellBuchanan, Apr 11 2008
  

       8th of 7: my scope is not that broad. I want to limit oxygen in the very tiny environment of the root nodule. I have other, different ideas as regards remedies for the atmosphere.
bungston, Apr 11 2008
  

       Hmm, well I think it would just be easier to make a rhizobium that expresses more nitrogenase.
Cuit_au_Four, Apr 16 2008
  

       Making more of something you already have is much easier, and easily attainable by evolution. Getting any of something you do not have at all is a lot harder for evolution. Getting hemoglobin in the first place was an incredibly lucky evolutionary coup for the rhizobia.
bungston, Apr 16 2008
  

       [8th of 7] , that is really good. I mean, I like that a lot. Is that original?   

       [bungston] If a higher affinity hemoglobin worked better, they would probably have one. Presumably the binding needs to be reversible or something to function.
GutPunchLullabies, Apr 16 2008
  

       For [8th] proposal to work, you would need a lot of carbon-based strata. Where could one acquire the vast quantities necessary?
bungston, Apr 16 2008
  

       Does anyone else keep seeing hobgoblins in the title?   

       The problem with your regular hobgoblin is his naughty nature - this, in combination with legumic substances (broad beans, runner beans etc) often causes localised areas of temporal instability.   

       Much better to breed hobgoblins who exhibit improved manners and overall behaviour, thus reducing the incidence of back-garden space-time slippage.
zen_tom, Apr 17 2008
  
      
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