DOP-PCR based painting of rye chromosomes in a wheat background

Laser Capture Microdissection: From Genomes to Chromosomes, from Complex Tissue to Single-Cell Analysis

Laser microdissection (LM) is a powerful tool for various molecular analyses providing pure samples for genomic, transcriptomic, and proteomic studies. Cell subgroups, individual cells, or even chromosomes can be separated via laser beam from complex tissues, visualized under the microscope, and used for subsequent molecular analyses. This technique provides information on nucleic acids and proteins, keeping their spatiotemporal information intact. In short, the slide with tissue is placed under the microscope, imaged by a camera onto a computer screen, where the operator selects cells/chromosomes based on morphology or staining and commands the laser beam to cut the specimen following the selected path. Samples are then collected in a tube and subjected to downstream molecular analysis, such as RT-PCR, next-generation sequencing, or immunoassay.

St2-80: a new FISH marker for St genome and genome analysis in Triticeae

The St genome is one of the most fundamental genomes in Triticeae. Repetitive sequences are widely used to distinguish different genomes or species. The primary objectives of this study were to (i) screen a new sequence that could easily distinguish the chromosome of the St genome from those of other genomes by fluorescence in situ hybridization (FISH) and (ii) investigate the genome constitution of some species that remain uncertain and controversial. We used degenerated oligonucleotide primer PCR (Dop-PCR), Dot-blot, and FISH to screen for a new marker of the St genome and to test the efficiency of this marker in the detection of the St chromosome at different ploidy levels. Signals produced by a new FISH marker (denoted St₂-80) were present on the entire arm of chromosomes of the St genome, except in the centromeric region. On the contrary, St₂-80 signals were present in the terminal region of chromosomes of the E, H, P, and Y genomes. No signal was detected in the A and B genomes, and only weak signals were detected in the terminal region of chromosomes of the D genome. St₂-80 signals were obvious and stable in chromosomes of different genomes, whether diploid or polyploid. Therefore, St₂-80 is a potential and useful FISH marker that can be used to distinguish the St genome from those of other genomes in Triticeae.

Isolation and application of P genome-specific DNA sequences of Agropyron Gaertn. in Triticeae

Different types of P genome sequences and markers were developed, which could be used to analyze the evolution of P genome in Triticeae and identify precisely wheat- A. cristatum introgression lines. P genome of Agropyron Gaertn. plays an important role in Triticeae and could provide many desirable genes conferring high yield, disease resistance, and stress tolerance for wheat genetic improvement. Therefore, it is significant to develop specific sequences and functional markers of P genome. In this study, 126 sequences were isolated from the degenerate oligonucleotide primed-polymerase chain reaction (DOP-PCR) products of microdissected chromosome 6PS. Forty-eight sequences were identified as P genome-specific sequences by dot-blot hybridization and DNA sequences analysis. Among these sequences, 22 displayed the characteristics of retrotransposons, nine and one displayed the characteristics of DNA transposons and tandem repetitive sequence, respectively. Fourteen of 48 sequences were determined to distribute on different regions of P genome chromosomes by fluorescence in situ hybridization, and the distributing regions were as following: all over P genome chromosomes, centromeres, pericentromeric regions, distal regions, and terminal regions. We compared the P genome sequences with other genome sequences of Triticeae and found that the similar sequences of the P genome sequences were widespread in Triticeae, but differentiation occurred to various extents. Additionally, thirty-four molecular markers were developed from the P genome sequences, which could be used for analyzing the evolutionary relationship among 16 genomes of 18 species in Triticeae and identifying P genome chromatin in wheat-A. cristatum introgression lines. These results will not only facilitate the study of structure and evolution of P genome chromosomes, but also provide a rapid detecting tool for effective utilization of desirable genes of P genome in wheat improvement.

The Chromosome Microdissection and Microcloning Technique

Chromosome microdissection followed by microcloning is an efficient tool combining cytogenetics and molecular genetics that can be used for the construction of the high density molecular marker linkage map and fine physical map, the generation of probes for chromosome painting, and the localization and cloning of important genes. Here, we describe a modified technique to microdissect a single chromosome, paint individual chromosomes, and construct single-chromosome DNA libraries.