Ohmido, N. | Search bioRxiv

bioRxiv2024

Allopolyploidy enhances survival advantages for urban environments in the native plant genus Commelina

Background and AimsUrbanization-induced environmental changes have profound effects on the geographical distribution limits in natural plant species. Polyploidization, an influential dynamic genome change, may determine survival potentials of plant species in urban environments. This study focused on the native plants, Commelina communis L. (Cc) and closely related subspecies, C. communis f. ciliata (Masam.) Murata (Ccfc) which have different chromosome numbers (e.g. Cc: 2n = 88, Ccfc: 2n = 46). The aim is to investigate polyploidization effects on natural plant distribution in urban environments. MethodsThe geographical distribution across urban-rural gradients was investigated at a total of 218 sites in Japan. Stomata size and density were measured and compared between Cc and Ccfc. Flow cytometry was used to determine genome size and polyploidy. Chromosome karyotyping was performed by using the GISH method. Key resultsUrban areas were exclusively dominated by Cc, while Cc and Ccfc coexisted in rural areas. Cc had larger and fewer stomata and more than twice genome size than Ccfc. GISH results indicated that Cc possesses Ccfc and another unknown genome, suggesting allopolyploidy. ConclusionsThese results show that the ploidy difference affects the geographical distribution, the stomata traits, and genome size between Cc and Ccfc. In addition, GISH results indicate that Cc has Ccfc and another unknown genome, suggesting Cc is an allopolyploid and these two species of the genus Commelina are distinct. Therefore, not only polyploid but also allopolyploid contributes to Cc to enhance survival potentials in urban environments compared to Ccfc. This is the first investigation to clarify the distribution difference related to urban environments, the difference in stomata traits and genome size, and to conduct chromosome composition in Commelina species.

ecology↗

bioRxiv2024

Repeatome landscapes and cytogenetics of hortensias provide a framework to trace Hydrangea evolution and domestication

Background and AimsOrnamental hortensias are bred from a reservoir of over 200 species in the genus Hydrangea s.l. and are valued in gardens, households and landscapes across the globe. The phenotypic diversity of hortensia cultivars, hybrids and wild relatives is mirrored by their genomic variation, with differences in genome size, base chromosome numbers and ploidy level. We aim to understand the genomic and chromosomal basis of hortensia genome variation. Therefore, we analyze six hortensias with different origins and chromosomal setups for repeatome divergence, the genome fraction with the highest sequence turnover. This holds information from the hortensias evolutionary paths and can inform breeding initiatives. MethodsWe compiled a hortensia genotype panel representing members of the sections Macrophyllae, Hydrangea, Asperae, and Heteromallae and reconstructed a plastome-based phylogenetic hypothesis as evolutionary basis for all our analyses. We comprehensively characterized the repeatomes by whole genome sequencing and comparative repeat clustering. Major tandem repeats were localized by multi-color FISH. Key ResultsThe Hydrangea species show differing repeat profiles reflecting their separation into the two major Hydrangea clades: Diploid Hydrangea species from Japan show a conserved repeat profile, distinguishing them from Japanese polyploids as well as Chinese and American hortensias. These results are in line with plastome-based phylogenies. The presence of specific repeats indicates that H. paniculata was not polyploidized directly from the common ancestor of Japanese Hydrangea species, but evolved from a distinct progenitor. Major satellite DNAs were detected over all H. macrophylla chromosomes. ConclusionsRepeat composition among the Hydrangea species varies in congruence with their origins and phylogeny. Identified species-specific satDNAs may be used as cytogenetic markers to identify Hydrangea species and cultivars, and to infer parental species of old Hydrangea varieties. This repeatome and cytogenetics information helps to expand the genetic toolbox for tracing hortensia evolution and informing future hortensia breeding.

genomics↗