Fluorescence In Situ Hybridization (FISH) Analysis of the Locations of the Oligonucleotides 5S rDNA, (AGGGTTT)3, and (TTG)6 in Three Genera of Oleaceae and Their Phylogenetic Framework

Abstract

We report the cytogenetic map for a collection of species in the Oleaceae, and test similarities among the karyotypes relative to their known species phylogeny. The oligonucleotides 5S ribosomal DNA (rDNA), (AGGGTTT)3, and (TTG)6 were used as fluorescence in situ hybridization (FISH) probes to locate the corresponding chromosomes in three Oleaceae genera: Fraxinus pennsylvanica, Syringa oblata, Ligustrum lucidum, and Ligustrum × vicaryi. Forty-six small chromosomes were identified in four species. (AGGGTTT)3 signals were observed on almost all chromosome ends of four species, but (AGGGTTT)3 played no role in distinguishing the chromosomes but displayed intact chromosomes and could thus be used as a guide for finding chromosome counts. (TTG)6 and 5S rDNA signals discerned several chromosomes located at subterminal or central regions. Based on the similarity of the signal pattern (mainly in number and location and less in intensity) of the four species, the variations in the 5S rDNA and (TTG)6 distribution can be ordered as L. lucidum < L. × vicaryi < F. pennsylvanica < S. oblata. Variations have observed in the three genera. The molecular cytogenetic data presented here might serve as a starting point for further larger-scale elucidation of the structure of the Oleaceae genome, and comparison with the known phylogeny of Oleaceae family.

Distinguishing Sichuan Walnut Cultivars and Examining Their Relationships with Juglans regia and J. sigillata by FISH, Early-Fruiting Gene Analysis, and SSR Analysis

“…The FISH 5S rDNA oligonucleotide with two signals and (AG 3 T 3 ) 3 with an end signal on every chromosome showed almost no differences among the four walnut cultivars in this study. Similar distribution patterns have also been observed in Citrus species (Deng et al, 2019); Berberis species (Liu and Luo, 2019); and Fraxinus, Syringa, and Ligustrum species (Luo and Liu, 2019a). FISH probes (AG 3 T 3 ) 3 located at chromosome ends ensure accurate chromosome counts (Pereira et al, 2018), although (AG 3 T 3 ) 3 is also occasionally observed in the internal positions of chromosomes (Murray et al, 2002;Majerová et al, 2014;Vasconcelos et al, 2018).…”

“…The hidden centromeres of the small chromosomes hampered further karyotype analysis. A similar phenomenon has also been observed in Fraxinus pennsylvanica, Syringa oblata, Ligustrum lucidum, and Ligustrum × vicaryi (Luo and Liu, 2019a) as well as in Zanthoxylum armatum (Luo et al, 2018). The limited karyotype data contributed little to the identification of the walnut cultivars.…”

“…It is difficult for FISH to discern interspecific and intraspecific differences (Liu and Luo, 2019;Luo and Liu, 2019a). In addition, it is rather hard to prepare well-distributed chromosomes and FIGURE 7 | Allele sizes of 21 SSR loci of the four artificial hybrid cultivars and five natural hybrid cultivars.…”

“…At least five molecular genetic linkage maps for walnut have been established (Fjellstrom and Parfitt, 1994;Woeste et al, 1996;Malvolti et al, 2001;Luo et al, 2015;Zhu et al, 2015). Fluorescence in situ hybridization (FISH) with probe-labeled chromosome ends enables accurate counting of small walnut chromosomes (Deng et al, 2019;Liu and Luo, 2019;Luo and Liu, 2019a). Karyotype analysis aids in chromosome physical map construction and chromosome assembly (Hizume et al, 2002;Luo et al, 2017;Luo et al, 2018;Pereira et al, 2018), thereby providing a guide for distinguishing Sichuan walnut cultivars to a certain degree.…”

Genetic relationship study of some Vicia species by FISH and total seed storage protein patterns

“…Application of double or multiple probe FISH enables the discrimination of the homologous chromosomes and explores the structural genome changes among many species. It helps to clarify genetic maps and to assign linkage groups to physically marked chromosomes as well [15][16][17][18]. Florescence in situ hybridization has been applied in different Vicia species [19][20][21][22][23][24][25].…”