AUTHOR=Farhat Perla , Mandáková Terezie , Divíšek Jan , Kudoh Hiroshi , German Dmitry A. , Lysak Martin A. 

TITLE=The evolution of the hypotetraploid Catolobus pendulus genome – the poorly known sister species of Capsella

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1165140

DOI=10.3389/fpls.2023.1165140

ISSN=1664-462X

ABSTRACT=<p>The establishment of <italic>Arabidopsis</italic> as the most important plant model has also brought other crucifer species into the spotlight of comparative research. While the genus <italic>Capsella</italic> has become a prominent crucifer model system, its closest relative has been overlooked. The unispecific genus <italic>Catolobus</italic> is native to temperate Eurasian woodlands, from eastern Europe to the Russian Far East. Here, we analyzed chromosome number, genome structure, intraspecific genetic variation, and habitat suitability of <italic>Catolobus pendulus</italic> throughout its range. Unexpectedly, all analyzed populations were hypotetraploid (2<italic>n</italic> = 30, ~330 Mb). Comparative cytogenomic analysis revealed that the <italic>Catolobus</italic> genome arose by a whole-genome duplication in a diploid genome resembling Ancestral Crucifer Karyotype (ACK, <italic>n</italic> = 8). In contrast to the much younger <italic>Capsella</italic> allotetraploid genomes, the presumably autotetraploid <italic>Catolobus</italic> genome (2<italic>n</italic> = 32) arose early after the <italic>Catolobus</italic>/<italic>Capsella</italic> divergence. Since its origin, the tetraploid <italic>Catolobus</italic> genome has undergone chromosomal rediploidization, including a reduction in chromosome number from 2<italic>n</italic> = 32 to 2<italic>n</italic> = 30. Diploidization occurred through end-to-end chromosome fusion and other chromosomal rearrangements affecting a total of six of 16 ancestral chromosomes. The hypotetraploid <italic>Catolobus</italic> cytotype expanded toward its present range, accompanied by some longitudinal genetic differentiation. The sister relationship between <italic>Catolobus</italic> and <italic>Capsella</italic> allows comparative studies of tetraploid genomes of contrasting ages and different degrees of genome diploidization.</p>