Date of Award:

5-1-1995

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology (Molecular Biology)

Committee Chair(s)

Elizabeth Hood

Committee

Elizabeth Hood

Committee

Anu Singh-Cundy

Committee

Lance Seefeldt

Committee

Richard Mueller

Abstract

The objective of this research was to evaluate whether genes encoding certain classes of cell wall protein and pathogenesis-related protein are regulated in response to pollen tube growth, in maize silk. In Northern blot analysis of total RNA isolated from maize silk at different time periods after pollination, there was an increase in the transcripts for extensin, a cell wall protein. However, there was an increase in transcripts for mock pollinated samples, albeit to a lesser extent, indicating that there is a wound response as well. In contrast, PR-4, a pathogenesis-related protein gene, was induced only 24 hr after pollination, and this transcript was not wound inducible. We further evaluated extensin gene regulation by doing Western blot analysis and in situ localization. Western blot analysis with the extensin probe showed that there was increased accumulation of the protein along a time course of pollination, and this increase was detectable to a lesser extent in mock pollinated samples. The in situ localization experiment indicated that extensin accumulation occurred in all cell types in the cross section of maize instead of being localized exclusively or preferentially in the transmitting tissue. Based on these results we suggest that there is similarity between the silk tissue response to pollen tube invasion and the response of other plant tissues to pathogen invasion. However, the extensin and PR-4 genes are not likely to be directly involved in pollen tube growth and guidance. Instead, the induction of these genes might be a prophylactic response to protect the flower from secondary infections.

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