Genome and Chromosome Evolution

In cytology, the chromosome and genome evolution, as studied in the context of molecular phylogenetic hypotheses, is of particular interest to me and my collaborators. Our main focus in the family Gesneriaceae, is on genera where robust molecular phylogenies exist, such as Aeschynanthus, Agalmyla, Streptocarpus. Here we are interested in understanding the evolution of basic chromosome numbers, as suggested by the phylogenetic trees. Great variations can be found in the patterns of changes of basic numbers between related genera; while Streptocarpus is rather conservative showing only one change in basic number, the genus Aeschynanthus displays several parallel changes in the basic chromosome number.

Ribosomal DNA are arranged in hundreds of copies in tandem arrays in at least one nucleolar organiser region (NOR) per haploid genome per cell. We founds that in Streptocarpus at least, these NOR sites are inherited as a single unit (or locus) rather than as mosaic sequences of both parents as found in some other plants, such as Amelanchier or Ilex. This has important implications on the interpretation of phylogenetic trees where hybridisation is involved.

We also study chromosomal markers, such as the ribosomal DNA sites, the data source for numerous phylogenetic analyses, for which fluorescent probes exist. Fluorescent in situ hybridisation (FISH) is particularly helpful in cases where no variation in chromosome numbers exist between species. We analysed selected genera of Gesneriaceae for their variation in these markers using FISH. Our initial results show that different, genus specific patterns exist in Gesneriaceae.

Over recent years, our living research collection has increased dramatically, allowing cytotaxonomic studies to proceed. Currently, we determine the basic chromosome numbers of taxa not previously examined focusing on newly defined genera, based on our molecular phylogenetic work.

With input from M. Kiehn (University of Vienna), L. Skog (Smithsonian Institution, Washington) and M. Pullan (RBGE) we provide a webbrowser-based database for cytological investigations on Gesneriaceae, ‘WebCyte'. This research tool allows easy access to all current cytological data published for the family.

Current Projects:

Chromosome and genome evolution across Gesneriaceae (with Frieda Christie, Sadie Barber, RBGE)

Recent Projects:

Chromosome numbers among the newly defined genera in Old World Gesneriaceae (with Frieda Christie, Sadie Barber, RBGE)

Evolution of rDNA in selected genera of Old World Gesneriaceae (with Dr Goro Kokubugata, Tsukuba Botanical Garden; Dr Kwiton Jong, RBGE)

Publications (chronologically):

Christie F, S Barber, M MÖLLER (2012). New chromosome counts in Old World Gesneriaceae: numbers for species hitherto regarded as Chirita, and their systematic and evolutionary significance. Edinburgh Journal of Botany 69(2): 323-345.

MÖLLER M, G Kokubugata, K Jong (2008). Aspects of genome evolution in Gesneriaceae: patterns of 45S-nrDNA site evolution based on evidence from fluorescent in-situ hybridization (FISH). International Journal of Plant Sciences 169(5): 667-676. 

Denduangboripant J, QCB Cronk, G Kokubugata, M MÖLLER (2007). Variation and inheritance of nuclear ribosomal DNA clusters in Streptocarpus (Gesneriaceae) and their biological and phylogenetic implications. International Journal of Plant Sciences 168(4):455-467.

Jong K, M MÖLLER (2000). New chromosome counts in Streptocarpus (Gesneriaceae) from Madagascar and the Comoro Islands and their taxonomic significance. Plant Systematics and Evolution 224:173-182.

MÖLLER M, M Kiehn (2004). A synopsis of cytological studies in Gesneriaceae. Edinburgh Journal of Botany 60(3):425-447.

Zhou P, ZJ Gu, M MÖLLER (2004). New chromosome counts and nuclear characteristics for some members of Gesneriaceae subfamily Cyrtandroideae from China and Vietnam. Edinburgh Journal of Botany 60(3):449-466.

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Chromosome counts of species hitherto belonging to Chirita (Christie et al 2012).

Chromosome counts of species hitherto belonging to Chirita (Christie et al 2012).

The Royal Botanic Garden Edinburgh is a charity (registration number SC007983)