Submitted to: Plant Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/1996
Publication Date: N/A
Interpretive Summary: This investigation was conducted to learn more about the genetic control of plant reproduction, especially apomixis. Apomixis is an asexual form of reproduction where seed are produced without fertilization and it can be used to develop true-breeding uniform varieties. Because apomixis does not occur in economically important grain crops, the most feasible approach of transferring this trait into crop plants is to isolate the genes for apomixis from apomictic plants and introduce them into a target crop species using molecular techniques. A technique known as differential display was used to compare gene expression in tissue from flowers of both sexual and apomictic buffelgrass plants. Several different genes were expressed, isolated and characterized. Four of these were specific to the ovaries in the flowers of both sexual and apomictic plants. One gene was expressed only in ovaries of the sexual plant, two were present in ovaries from the apomictic plant, and one was present in ovaries of both the sexual and apomictic plants. These findings are of significance because they show differences in gene expression in sexual and apomictic plants and represent the first step in identifying and isolating the genes controlling apomixis in buffelgrass.
Technical Abstract: Limited emphasis has been given to the molecular study of apomixis, an asexual method of reproduction where seed are produced without fertilization. Most genotypes of buffelgrass (Pennisetum ciliare (L.) Link syn=Cenchrus ciliaris) genotypes reproduce by obligate apomixis (apospory); however, rare sexed plants have been recovered. A modified differential display procedure was used to compare gene expression in unpollinated ovaries containing ovules with cellularized sexual or apomictic female gametophytes. The modification incorporated end-labeled poly(A+) anchored primers as the only isotopic source, and was a reliable and consistent approach for detecting differentially displayed transcripts. Using 20 different decamers and two anchor primers, 2268 cDNA fragments between 200 and 600 base pairs were displayed. From these, nine reproducible differentially displayed cDNAs were identified and cloned. Based on Northern analysis, one cDNA was detected in only the sexual ovaries, two cDNAs in only apomictic ovaries and one cDNA was present in both types of ovaries. Four fragments could not be detected and one fragment was detected in ovaries, stems, and leaves. Comparison of gene expression during sexual and apomictic development in buffelgrass represents a new model system and strategy for investigating female reproductive development in the angiosperms.