Cloning and Characterization of Chromosomal Markers from a Cot-1 Library of Peanut (<b><i>Arachis hypogaea</i></b> L.)

Abstract

The cultivated peanut, Arachis hypogaea (AABB, 2n = 40), is an allotetraploid which was probably originated from a hybridization event between 2 ancestors, A. duranensis (A genome) and A. ipaensis (B genome) followed by chromosome doubling. The wild species in the Arachis section are useful genetic resources for genes that confer biotic and abiotic stress resistance for peanut breeding. However, the resource is not well exploited because little information on the genetic, cytogenetic, and phylogenetic relationships between cultivated peanut and its wild relatives is known. Characterization of its chromosome components will benefit the understanding of these issues. But the paucity of information on the DNA sequence and the presence of morphologically similar chromosomes impede the construction of a detailed karyotype for peanut chromosome identification. In our study, a peanut Cot-1 library was constructed to isolate highly and moderately repetitive sequences from the cultivated peanut, and the chromosomal distributions of these repeats were investigated. Both genome and chromosome specific markers were identified that allowed the distinguishing of A and B genomes in tetraploid peanut and a possible karyotyping of peanut chromosomes by FISH. In particular, a 115-bp tandem repetitive sequence was identified to be a possible centromere repetitive DNA, mainly localized in the centromeres of B chromosomes, and a partial retrotransposable element was also identified in the centromeres of B chromosomes. The cloning and characterization of various chromosomal markers is a major step for FISH-based karyotyping of peanut. The FISH markers are expected to provide a reference tool for sequence assembly, phylogenetic studies of peanut and its wild species, and breeding.

Identification of peanut (Arachis hypogaea) chromosomes using a fluorescence in situ hybridization system reveals multiple hybridization events during tetraploid peanut formation

“…In a previous report, we cloned a centromere satellite repeat (B‐c) and a retrotransposon fragment in peanut (Zhang et al ., ). In this study, another centromere‐specific satellite repeat H‐b was cloned and localized mostly in the pericentromeric regions of A‐genome chromosomes.…”

“…Seeds of cultivated peanut ( Arachis hypogaea L.) from China were the same as previously described (Zhang et al ., ). All other tetraploid peanut varieties (PI 119876, PI 119203, PI 119238 and PI 170236) and diploid wild peanut Arachis duranensis Krapov.…”

“…Cot‐1 DNA was prepared as described previously with modifications (Zhang et al ., ). Genomic DNA from a diploid species ( A. duranensis ) was isolated from young leaves.…”

“…All probes were labeled with Alexa Fluor 594‐ 5‐dUTP (Thermo Fisher Scientific) and hybridized to metaphase chromosomes of peanut according to Zhang et al . ().…”

Construction and Characterization of a Repetitive DNA Library in Parodontidae (Actinopterygii: Characiformes): A Genomic and Evolutionary Approach to the Degeneration of the W Sex Chromosome

“…38 Thus, numerous studies identified and physically mapped repetitive sequences to assist in the organization of chromosomal regions rich in repetitive DNA, particularly in heteromorphic sex chromosomes. [39][40][41] C o t-1 DNA is a useful tool to isolate highly and moderately repetitive DNAs, according to Ferreira and Martins 42 and Zhang et al 43 In this study, we described different types of repetitive sequences isolated from the Parodontidae C o t-1 library: satellite DNAs, minisatellite DNAs, microsatellite DNAs, DNA transposons, and retrotransposons. Physical mapping of the total C o t-1 probe revealed locations in the terminal regions of some autosomes, as well as in the proximal region of the short arm of the Z chromosome and in the long arm of the W chromosome of the Apareiodon sp.…”