Developmental comparisons of sexual and aposporous female gametophytes in Pennisetum ciliare (L.) Link /
Buffelgrass (Pennisetum ciliare (L.) Link syn=Cenchrus
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1995.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742745711&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Buffelgrass (Pennisetum ciliare (L.) Link syn=Cenchrus ciliaris L.) is an aposporous apomict species in which rare sexual plants have been recovered. This work took advantage of this reproductive versatility by comparing female gametophyte development in full-sib sexual and apomictic genotypes selected from an Fl population segregating for method of reproduction. An ultrastructural comparison revealed differences in sexual and aposporous female gametophytes fixed 0 to 4 hours after pollination. In contrast to the sexual egg apparatus (synergids and egg cell), aposporous female gametophytes had premature and accelerated degeneration of the synergids, autonomous development of proembryos, and the presence of a cell wall covering the egg cell prior to pollen tube arrival. To better understand the molecular basis of cellular differences, gene expression was compared in ovaries of previously characterized genotypes. Differential display of mRNA in unpollinated ovaries containing cellularized female gametophytes revealed that approximately 20% of all stage- specific mRNA species follow the same patterns of transcription in mature ovaries of sexual and obligately apomictic plants. Differentially displayed cDNA fragments were isolated and cloned; poly(A+) RNA blots revealed that three cDNA fragments corresponded to moderately abundant transcripts specifically expressed in ovaries containing either sexual or aposporous female gametophytes. Arabinogalactan proteins (AGPs) epitopes that relate to positional sensing and cell determination were localized immunocytochemically in sexual and aposporous ovules. No differences in expression of these developmentally regulated AGP epitopes were detected between sexual and aposporous female gametophytes. Localization of AGP epitopes in the ovular extra-cellular matrix (ECM), the micropyle, and the synergids suggests that AGPs may contribute to pollen tube guidance. The localization of AGP epitopes was conserved in aposporous female gametophytes aberrantly positioned with respect to the micropylar-chalazal axis, and suggests that positional sensing is not essential for gametophytic cell determination. Overall, the results of this study indicate that developmental comparisons of sexual and apomictic female gametophytes represent a valuble method to obtain information on specific cellular and molecular aspects of plant reproduction. |
|---|---|
| Item Description: | Vita. "Major Subject: Plant Breeding". |
| Physical Description: | x, 63 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |