Chinese scientists have made new progress in genomic research of Meliaceae medicinal plants, revealing that multiple hybridization and polyploidization events have shaped the complex species formation history of Meliaceae. The related findings were published in "The Plant Journal".
Meliaceae comprises over 2000 species, most of which have medicinal properties. The species in Meliaceae exhibit various chromosomal ploidy levels and complex evolutionary histories, with intricate phylogenetic relationships between the Aglaia and Chukrasia genera.
The study assembled high-quality (without collapse) phased genomes of the octoploid medicinal plant Aglaia odorata and the octoploid medicinal plant Chukrasia tabularis, with 103 and 104 chromosomes respectively, totaling 4.88 Gb and 1.82 Gb in size. Additionally, the published tetraploid species Aglaia and diploid species Chukrasia genomes were reconstructed, and analyses were conducted on the species formation history of related taxa, including phylogenetic relationships, divergence time estimation, and Ks distribution curves.
The research indicates that around 48 million years ago, the ancestral species of Meliaceae, Ancestor I (2n=2x=26), diverged into the diploid Ancestor II (2n=2x=26) and Ancestor III (2n=2x=26). The latter split into Ancestor-A and Ancestor-B (2n=2x=26) around 35 million years ago, undergoing hybridization and polyploidization events, leading to the ancient tetraploid ancestor Ancestor-AB (2n=4x=52) of Aglaia and the tetraploid ancestor Sauropus clade (2n=4x=52) of Chukrasia around 30 million years ago. Subsequently, the diploid ancestor group of Chukrasia experienced a homoploid hybridization or autopolyploidization event (p-WGD-2), giving rise to the homologous allopolyploid species Chukrasia tabularis (2n=8x=104).
The ancestral group of Aglaia diverged into two branches, with one evolving into the tetraploid species Aglaia (2n=4x=52) and the other undergoing differentiation, hybridization polyploidization, chromosome loss, ultimately evolving into the extant non-whole-genome-duplicated octoploid species Aglaia odorata (2n=8x=103).
This study, conducted by the Crop Research Institute of Guangdong Academy of Agricultural Sciences, in collaboration with the Special Crops and Southern Medicine Team of South China Agricultural University, Nanjing Forestry University, Institute of Agricultural Genomics of Chinese Academy of Agricultural Sciences, and South China Normal University, provides initial insights into the significant role of hybridization and polyploidization events in the formation of Meliaceae.
Related paper information: https://doi.org/10.1111/tpj.16767
