| A floral transmitting tissue-specific protein, TTS protein, has been characterized. Protein blots and immunolocalization experiments show that TTS proteins are highly glycosylated proteins localized to the extracellular matrix of transmitting tissue cells through which pollen tubes elongate in the style. The levels of TTS proteins are regulated during pistil development and by pollination, and these levels are apparently correlated with the capacity of the pistil to support pollen tube growth. Pollination also qualitatively affects TTS proteins. A 30 kD underglycosylated TTS protein species accumulates in pollinated styles, suggesting that pollen tubes may deglycosylate TTS proteins and use the sugars as nutrients. This suggestion is strongly supported by the recent results from in vitro experiments. Moreover, TTS proteins display a gradient of increasing glycosylation along the style coincident with the direction of pollen tube growth. This protein-bound sugar gradient might be involved in providing directional cues for pollen tube growth. In order to further examine the functions of TTS proteins, transgenic tobacco plants with 35S-promoter:sense TTS and TTS-promoter:antisense TTS constructs have been generated. Microscopic and interrupted pollination studies show that pollen tube growth rate is reduced in the styles of the transgenic plants with highly reduced TTS protein levels as a result of antisense- or sense-suppression. Taken together, these results suggest that TTS proteins play important roles in supporting the optimal in vivo pollen tube growth.;Pollination is known to induce a broad spectrum of responses in the pistil. I found that pollination induces poly(A) tail-shortening in at least three major classes of transmitting tissue-specific mRNAs, TTS,... |
