The genome sequence of Hirschfeldia incana, a new Brassicaceae model to improve photosynthetic light-use efficiency

Photosynthesis is a key process in sustaining plant and human life. Improving the photosynthetic capacityof agricultural crops is an attractive means to increase their yields. While the core mechanisms of photosyn-thesis are highly conserved in C3plants, these mechanisms are very flexible, allowing considerable diversityin photosynthetic properties. Among this diversity is the maintenance of high photosynthetic light-use effi-ciency at high irradiance as identified in a small number of exceptional C3species.Hirschfeldia  incana,amember of the Brassicaceae family, is such an exceptional species, and because it is easy to grow, it is anexcellent model for studying the genetic and physiological basis of this trait. Here, we present a referencegenome ofH. incanaand confirm its high photosynthetic light-use efficiency. WhileH. incanahas the high-est photosynthetic rates found so far in the Brassicaceae, the light-saturated assimilation rates of closelyrelatedBrassica  rapaandBrassica  nigraare also high. TheH.  incanagenome has extensively diversifiedfrom that ofB. rapaandB. nigrathrough large chromosomal rearrangements, species-specific transposonactivity, and differential retention of duplicated genes. Duplicated genes inH. incana,B. rapa, andB. nigrathat are involved in photosynthesis and/or photoprotection show a positive correlation between copy num-ber and gene expression, providing leads into the mechanisms underlying the high photosynthetic effi-ciency of these species. Our work demonstrates that theH. incanagenome serves as a valuable resource forstudying the evolution of high photosynthetic light-use efficiency and enhancing photosynthetic rates incrop species