Submitted to: Annual International Plant & Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: 11/2/2004
Publication Date: 1/14/2005
Citation: Jessup, R.W., Burson, B.L., Burow, G.B., Paterson, A.H., Hussey, M.A. 2005. Comparative mapping of a segregation distorter system on the buffelgrass chromosome conferring apomixis [abstract]. Plant and Animal Genome XIII Conference. p. 46.
Technical Abstract: Genetic elements that distort Mendelian segregation have been implicated in many fundamental aspects of sexual reproduction. A region of segregation distortion (SD) occurs on buffelgrass linkage group (LG) 7b near the PApo1 locus, which confers major control over apomixis (asexual reproduction through seed). Comparative mapping revealed that this region in buffelgrass is syntenic to maize chromosome 10L, in which a meiotic drive system occurs with the presence of abnormal chromosome 10 (Ab10). The region of SD in buffelgrass LG 7b has several features in common with the Ab10 meiotic drive system in maize: 1) transmission ratio distortion only through maternal gametophytes, 2) transmission levels approaching 75%, 3) heterochromatic (repetitive) elements, 4) close proximity to centromeric signals, 5) suppressed recombination, and 6) chromosomal rearrangements. These results suggest that the SD locus in buffelgrass LG 7b is a region of chromosomal meiotic drive. Changes in heterochromatin would be expected in chromosomal meiotic drive systems and could quantitatively alter gene expression near PApo1 through position-effect variegation. The effect of this genetic mechanism would explain several characteristics of apomixis in buffelgrass (partial lethality, facultativeness, environmental/ seasonal effects, etc.). Implications of these findings in understanding the underlying genetics of apomixis will be discussed.