Insight into the Chromosome Structure of the Cultivated Tetraploid Alfalfa (Medicago sativa subsp. sativa L.) by a Combined Use of GISH and FISH Techniques

Abstract

Cytogenetic research in Medicago sativa subsp. sativa L., the cultivated tetraploid alfalfa (2n = 4x = 32), has lagged behind other crops mostly due to the small size and the uniform morphology of its chromosomes. However, in the last decades, the development of molecular cytogenetic techniques based on in situ hybridization has largely contributed to overcoming these limitations. The purpose of this study was to extend our knowledge about the chromosome structure of alfalfa by using a combination of genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH) techniques. The results of self-GISH (sGISH) suggested that a substantial part of the repetitive fraction of the genome of subsp. sativa is constituted by tandem repeats typical of satellite DNA. The coincidence of sGISH and C-banding patterns supported this assumption. The FISH mapping of the Arabidopsis-type TTTAGGG telomeric repeats demonstrated, for the first time, that the alfalfa telomeres consist of this type of sequence and revealed a massive presence of interstitial telomeric repeats (ITRs). In the light of this finding M. sativa appears to be a suitable material for studying the origin and function of such extra telomeric repeats. To further exploit this result, investigation will be extended to the diploid subspp. coerulea and falcata in order to explore possible connections between the distribution of ITRs, the ploidy level, and the evolutionary pathway of the taxa.

Interstitial Arabidopsis-Type Telomeric Repeats in Asteraceae

“…Another relevant question is whether ITR polymorphism is an odd genomic feature that is particularly represented in Asteraceae or it also affects other groups of angiosperms. In Fabaceae, the second most sampled family in flowering plants, the presence of ITRs have been assessed in 56 species included in 15 genera [7,8,44,, where they were detected in seven not-closely related tribes (Cassiieae, Fabeae, Phaseoleae, Cicereae, Dalbergieae, Loteae and Trifolieae) [56,57,59,[64][65][66]68,[71][72][73][74]. Three genera belonging to different tribes showed both the presence and absence of ITRs (Phaseolus, Senna, Vicia) [8,44,57,61,65,67,70,71,73,74] and intraspecific variation has been reported in Vicia faba [8,44,61].…”

Geçmişten Günümüze Genetik ve Kromozom Mühendisliği Çalışmalarının Sürdürülebilir Tarım ve Bitki Islahına Katkısı

“…Bitki türlerinin büyük çoğunluğu poliploid yapıya sahip olduğundan, genom organizasyonunun ayrıntılarının keşfinde ve genomlar arası benzerlik ve farklılıkların belirlenmesinde GISH tekniğinden yararlanılmaktadır (Shamim ve Armstrong, 2019). Güncel literatür incelendiğinde; allopoliploid Brassica juncea (Shamim ve Armstrong, 2019), Medicago sativa (Falistocco, 2020) gibi çok sayıda bitki türünde GISH tekniği kullanılarak genom yapılarının aydınlatılması ve karyotiplerinin oluşturulması sağlanmıştır.…”

Chromosomal dynamics in Senna: comparative PLOP–FISH analysis of tandem repeats and flow cytometric nuclear genome size estimations

“…It aids in the visualization of the DNA probes located on chromosomes within the nucleus, revealing information pertaining to chromosome structure, genome organization, and gene expression ( Iovene et al., 2008 ; Waminal et al., 2018 ). FISH is particularly useful in plant breeding programs for investigating the evolutionary relationships between plant species and studying the impact of environmental stressors on chromosome structure and behavior ( Sassi et al., 2019 ; Falistocco, 2020 ; de Moraes et al., 2021 ; Waminal et al., 2021 ).…”