Plants and Chloroplasts

Plant Cells and Chloroplasts

About a million years ago, a similar thing happened and the forerunners of plants took in a type of algae call (a free-living cyanobacteria – when it is inside the cell it is called a chloroplast). Again, this provides the energy for the cell, producing sugars by photosynthesis.

We know that symbiosis occurs fairly often with plants – some orchids need their own special type of companion fungus to grow, but that is not the same as internalising another cell.

This fits nicely with the chimera theme, but it is not the main point of the article in New Scientist (6th October 2014). Once again, it is  clear that the cyanobacteria has been taken into the original cell, and that the two have somehow fused together – instead of both propagating separately, they propagate together through one plant seedschematic of plant cell

However, the cyanobacteria were taken in a million years ago. In evolutionary terms, the cyanobacteria inside the plant has not evolved much – at that time, earth had very little oxygen in the atmosphere, and this has an effect on the key part of the photosynthesis process, the RuBisCo enzyme, which fixes CO2 from the air, takes in the carbon and energy, and releases O2 into the atmosphere.

Other cyanobacteria which have remained free (in the wild) have evolved much more than the plant ones, the plant enzymes only catalyses about 3 reactions a second, whereas wild ones are now much faster. The plant one is also inefficient in several other ways.

Scientists have now found a way to replace the RuBisCO enzyme in a tobacco plant with one from the wild, and this has lead to the hoped for increase in efficiency. This “turbocharged photosynthesis” gives a potential for “supercrops” with 25% higher yields.

This sounds great – it would remove more CO2, and we could food more people and better with the existing farmland. However, of course, there is a huge catch – the turbocharged plants would have a huge advantage over all the non-turbo ones, and could potentially lead to their extinction, and no doubt other consequences too. This is one of the ultimate GM modifications !

However, it does seem to prove that the union of original plant and cyanobacteria really did happen, and it removes any doubt from that (though the research doesn’t use a whole cyanobacteria, just an enzyme from one). Obviously, lots of questions remain as to how this wedding happened, and how it eventually produced seeds and all the varied plant species we see around us.