New insights into the evolution and local adaptation of the genus Castanea in east Asia

Chestnut plants ( ) are important nut fruit trees worldwide. However, little is known regarding the genetic relationship and evolutionary history of different species within the genus. How modern chestnut plants have developed local adaptation to various climates remains a mystery. The genomic data showed that first diverged in the Oligocene ~31.56 million years ago, followed by and the divergence between and occurred in the mid-Miocene. Over the last 5 million years, the population of chestnut plants has continued to decline. A combination of selective sweep and environmental association studies was applied to investigate the genomic basis of chestnut adaptation to different climates. Twenty-two candidate genes were associated with temperature and precipitation We also revealed the molecular mechanism by which interacts with and to promote the formation of non-glandular trichomes for adaptation to low temperature and high altitudes. We found a significant expansion of genes in Chinese chestnut ( ) and verified the regulation of adaptation to drought environments. These results shed light on the East Asian chestnut plants as a monophyletic group that had completed interspecific differentiation in the Miocene, and provided candidate genes for future studies on adaptation to climate change in nut trees.