Re-creation of a key step in the evolutionary switch from C3 to C4 leaf anatomy

The C4 Rice project aims to transition rice from a C3 crop to one that performs C4 photosynthesis, in order to realize a predicted 50% increase in yield.  Here, Wang et al. expressed a positive regulator of chloroplast development, the maize GOLDEN2-LIKE transcription factor, in rice.  The resulting plants displayed an increased organelle volume in sheath cells, as well as a greater number of plasmodesmata between mesophyll and sheath cells.  The sheath chloroplasts also accumulated the enzymes Rubisco, Rubisco activase and fructose-1,6-bisphosphatase, indicating a capacity for photosynthesis.  These phenotypes constitute a “proto-Kranz” anatomy – the first step on the C4 trajectory – and did not diminish plant fitness.  This work represents a huge step forwards for engineering C4 photosynthesis into rice. (Summary by Mike Page) Curr. Biol. 10.1016/j.cub.2017.09.040

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