The genome sequence of Hirschfeldia incana, a species with high photosynthetic light-use efficiency

Photosynthesis is a biophysical and biochemical process that plays a key role in sustaining plant and human life, being the first step in the production of energy-rich molecules and oxygen in the biosphere. Improving the photosynthetic capacity of agricultural crops is highly desirable to increase their yields. While the core mechanisms of photosynthesis are highly conserved, certainly in higher plants, plants that can maintain a high photosynthetic light-use efficiency at high irradiance are exceptional and may be useful to understand and improve high irradiance photosynthesis of crops. One such exceptional species is Hirschfeldia incana , a member of the well-studied Brassicaceae family that is easy to grow under standard laboratory conditions, providing an excellent resource for studying the genetic and physiological basis of this trait. Here, we present a reference assembly of H. incana and affirm its high photosynthetic efficiency relative to the Brassicaceae species Brassica rapa, Brassica nigra , and Arabidopsis thaliana . We estimate that it diverged from B. rapa and B. nigra 10-11 million years ago and that its genome has diversified from that of the latter two species through large chromosomal rearrangements, species-specific transposon activity, and differential retention of duplicated genes. Genes present at copy numbers different from B. rapa and B. nigra include those involved in photosynthesis and/or abiotic stress, which may mediate the high photosynthetic efficiency of H. incana . We expect the reference assembly of H. incana to be a valuable genomic resource for identifying ways to enhance photosynthetic rates in crop species. ### Competing Interest Statement The authors have declared no competing interest.