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Dr. Aretuza Sousa dos Santos




Curriculum Vitae

Research interests

Sex chromosome evolution, ancestral reconstruction of chromosomal changes, molecular cytogenetics, cytotaxonomy, next generation sequencing (NGS).

Fig. 1. Karyotype from Coccinia grandis male with 2n = 24, XY system after GISH experiment. Cell in A shows the chromosome set stained with DAPI; B displays the distribution of male genomic probe (green); C exhibits the distribution of the female genomic probe (red), and D shows the overlapping of A, B, and C. The Y chromosome is the largest chromosome of the complement, and shows no hybridization signals at the centromeric region for both genomic probes.

Using Coccinia grandis (Cucurbitaceae) to study the evolution of sex chromosomes in plants

This project focuses on the study of the sequence and chromatin characteristics of the sex chromosomes of the Cucurbitaceae Coccinia grandis. Previously, I showed that this species’ Y chromosome is the largest known in flowering plants and is mostly heterochromatic (Sousa et al., 2013); the difference between the male and female genomes is almost 0.1 pg of DNA. Inconveniently, the X chromosome can only be distinguished from the autosomes during meiosis, and the XY bivalent does not present rDNA signals.

For my postdoctoral research, which I am doing in collaboration of Andreas Houben and Jörg Fuchs at the IPK in Gatersleben, I am using the Illumina data from male and female genomes of C. grandis, the pipeline RepeatExplorer to compare repetitive fractions of DNA among sexes, and microdissection to separate the sex chromosomes for separate sequencing. The in silico analyses also serve to develop DNA probes for localizing the distribution of the main classes of repetitive DNA on the chromosomes and, ideally, also to develop sex-specific probes. The latter may also work in closely related species which homomorphic sex chromosomes, which would permit inferring evolutionary precursor stages. I will also use immunostaining to see if the chromatin composition differs between autosomes and sex chromosomes, which if true could help to identify sex chromosomes in other Coccinia species with undifferentiated karyotypes.

Sex chromosomes are poorly known in plants, and the only Y chromosome so far sequenced is that of the liverwort Marchantia polymorpha (Okada et al., 2001). My study of the Coccinia grandis sex chromosomes will contribute to a better understanding of the kinds of coding and non-coding DNA that makes up plant sex chromosomes.


Okada S., Sone T., Fujisawa M., Nakayama S., Takenaka M., Ishizaki K., Kono K., Shimizu-Ueda Y., Hamajiri T., Yamato K.T., Fukuzawa H., Brennicke A., Ohyama K. (2001): The Y chromosome in the liverwort Marchantia polymorpha has accumulated unique repeat sequences harboring a male-specific gene. PNAS 88: 9454–9459.

Sousa A., Fuchs, J., Renner S.S. (2013): Molecular cytogenetics (FISH, GISH) of Coccinia grandis, a c. 3 Ma-old species of Cucurbitaceae with the largest Y/autosome divergence in flowering plants. Cytogenetic and Genome Research 139: 107–118.

Last update: 2015-02-02