Carica papaya L. sex chromosome review and physical mapping of the serk 2, svp-like and mdar 4 sequences.

ABSTRACT

Physical mapping evidences the chromosome organization and structure. Despite the data about plant cytogenomics, physical mapping has been conducted from single-copy and/or low-copy genes for few species. Carica papaya cytogenomics has been accomplished from BAC-FISH and repeatome sequences. We aimed to map the serk 2, svp-like and mdar 4 sequences in C. papaya. The sequences were amplified and the amplicons sequenced, showing similarity in relation to serk 2, svp-like and mdar 4 genes. Carica papaya diploidy was confirmed and the mitotic chromosomes characterized. The chromosome 1 exhibited the secondary constriction pericentromeric to the centromere of the long arm. So, we concluded that it is the sex chromosomes. serk 2 was mapped in the long arm interstitial portion of the sex chromosomes, and the interphase nuclei showed two fluorescence signals. Considering these results and the sequencing data from the C. papaya sex chromosomes, svp-like and mdar 4 genes were mapped in the interstitial region of the sex chromosome long arm. Both sequences showed only one fluorescence signal in the interphase nuclei. The procedure adopted here can be reproduced for other single-copy and/or low-copy genes, allowing the construction of cytogenetic maps. In addition, we revisited the cytogenomics data about C. papaya sex chromosomes, presenting a revised point of view about the structure and evolution to these chromosomes.