Researchers report reference genome for corn B chromosome
Three groups (the group of Dr James Birchler of the University of Missouri, the group of Dr Jan Barto of the Institute of Experimental Botany of the Czech Academy of Sciences and the group of Dr HAN Fangpu of the Institute of Genetics and of Developmental Biology of the Chinese Academy of Sciences) recently reported a reference sequence for the supernumerary B chromosome in corn in a study published online in PNAS (doi: 10.1073 / pnas.2104254118).
Supernumerary B chromosomes persist in thousands of plant and animal genomes although they are not essential. They are maintained in populations by “drive” mechanisms that cause them to inherit at higher Mendelian rates than typical rates. Key properties such as its origin, evolution and the molecular mechanism of its accumulation in maize have remained uncertain even though these chromosomes have been a powerful tool for studying maize genetics.
The researchers used a well-established set of sequencing and mapping tools, including chromosome flow sorting, Illumina sequencing, Bionano optical mapping, and chromatin conformation capture (Hi-C).
The rich availability of suppression derivatives ensured strong scaffolding and assembly control. In addition, 758 genes encoding proteins have been identified from the 125.9 Mb of chromosomal sequence, of which at least 88 are expressed.
Scientists have discovered that the current content of the gene is the result of continuous transfer of chromosomal complement A over a prolonged period of development. This process was accompanied by subsequent degradation although selection for the maintenance of this non-vital chromosome also continued.
The results of the annotation demonstrate that the transposable elements in the B chromosome are shared with the set of standard A chromosomes. However, the failure of multiple lines of evidence to reveal a syntene region in the B chromosome with any A chromosome indicates that this chromosome has been present in the evolutionary lineage for millions of years since such synteny arose. is disintegrated.
Sequence and deletion analysis reveals that a specific DNA repeat is located in and around the centromere which is involved in its driving mechanism, consisting of nondisjunction at second pollen mitosis and preferential fertilization. from the egg by the sperm containing B.
This analysis cleverly combines comparisons between a variety of translocation and B deletion stocks as well as many years of genetic analysis. This approach provides a unique view of the sequence of this chromosome, as well as the characterization of potentially functional elements within it.
Warning: AAAS and EurekAlert! are not responsible for the accuracy of any press releases posted on EurekAlert! by contributing institutions or for the use of any information via the EurekAlert system.