Improving C3 photosynthesis by exploiting natural genetic variation: Hirschfeldia incana as a model species

Despite  research  efforts  toward  improving  crop  photosynthetic  energy  conver-sion  efficiencies  over  the  past  40  years,  photosynthetic  efficiencies  remain  far  from their theoretical maxima. A major challenge has been that plant photosyn-thesis  is  a  complex  process,  controlled  by  many  underlying  genetic  factors  and  highly  dynamic  in  response  to  short-  term  environmental  changes.  Recent  ap-proaches to improving photosynthesis involved model- based identification of the bottlenecks in photosynthesis followed by their genetic modification (GM). While these approaches were successful and inspirational, their dependency on the use of  GM  techniques  may  restrict  their  implementation  in  some  jurisdictions.  We  therefore  suggest  greater  research  focus  on  a  different,  yet  complementary,  ap-proach to improving photosynthetic efficiency: the exploration and exploitation of natural genetic variation in photosynthesis. A substantial improvement in phe-notyping and genotyping technology over the past decade has highlighted natu-ral  variation  in  photosynthetic  sub-  traits  for  crop  and  model  species.  However,  a comprehensive understanding of all the factors responsible for photosynthetic limitations is still lacking. We therefore propose the use of high photosynthetic capacity  species  as  models  for  the  exploration  of  the  physiological  and  genetic  basis of high photosynthetic efficiency. While most high photosynthetic capacity species are not suitable as models due to complex genetics and evolutionary dis-tance from crops, we have identified Brassicaceae species Hirschfeldia incana (L.) Lagr.- Foss as a promising candidate. In this perspective paper, we describe and advocate the use of H. incana as a model for the exploration of high maximum CO2  assimilation  rates  (Pmax)  found  in  some  C3  species.  We  describe  the  basic  biology  and  evolutionary  history  of  the  species  and  report  preliminary  data  on  its photosynthetic characteristics. Our findings suggest H. incana is an excellent model  species  for  studies  aiming  at  understanding  natural  genetic  variation  in  photosynthetic efficiency.