OAT-MAIZE CHROMOSOME ADDITION LINES: A NEW SYSTEM FOR MAPPING THE MAIZE GENOME

Authors: ANANIEV, EVGUENI - UNIVERSITY OF MINNESOTA; RIERA-LIZARAZU, OSCAR - UNIVERSITY OF MINNESOTA; Rines, Howard; PHILLIPS, RONALD - UNIVERSITY OF MINNESOTA

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Knowledge of the physical organization of the genetic make-up of our major crop, corn, is needed to effectively apply new molecular genetic engineering technologies to this crop. Such genetic manipulations provide the key for maintaining sustainable corn production and tailoring the crop for new market uses. We have recently reported the recovery of novel partial hybrids between the cereals oat and corn in which portions of the corn's genetic material (one of its ten chromosomes) are added to the genetic material of oat. In this follow-up report, we describe a means to selectively identify the genetic material (DNA sequences) of the corn genome that is being carried along in the oat plant. This selective scheme is based on our demonstration that the major portion of the genetic material of each of these species consists of highly repeated DNA sequences that are quite distinct between the two species. Furthermore, the species-specific DNA sequences are highly interspersed between the active genetic sequences of the species. We now plan to use radiation to break up the corn chromosome present in these novel oat plants so that small fragments of corn chromosomes will be incorporated into the oat chromosomes. These integrated small fragments of corn chromosome will then be selectively isolated. The isolated fragments will be used in a series of experiments to align overlapping fragments to obtain the detailed physical structure of corn's genetic material. An understanding of how the genetic material of corn is physically organized will aid in developing schemes to genetically modify corn for improved disease and stress resistance, higher nutritional quality, and special industrial uses.

Technical Abstract: Novel plants with individual maize chromosomes added to a complete oat genome have been recovered via embryo rescue from oat (Avena sativa L.) x maize (Zea mays L.) crosses. An oat-maize disomic addition line possessing 21 pairs of oat chromosomes and one maize chromosome 9 pair was used to construct a cosmid library. A mixture of highly repetitive maize specific sequences was used as a "multiprobe" (mixture of labeled fragments used as a probe) to selectively isolate cosmid clones containing maize genomic DNA. Characterization of individual maize cosmid clones or their subcloned fragments revealed that most high, middle, or low copy number DNA sequences may serve as maize specific DNA markers to identify maize genomic DNA in an oat genomic background. Chimeric cosmid clones were not found indicating that no significant exchanges of genetic material had occurred either between the maize addition chromosome and the oat genome or in the cloning process. These data allow us to consider oat as a host for the cloning of maize chromosomes or maize chromosome segments. Introgressing parts of the maize chromosome into the oat genome by irradiation will allow a library to be constructed of overlapping fragments for each individual maize chromosome in oat. The multiprobe screening approach will enable us to identify almost any maize chromosome segment. These corn-oat introgression lines with small segments of maize chromosomes will serve as a source of DNA for the construction of region specific libraries for maize chromosomes and eventually for construction of physical maps for maize chromosomes.