Characterization of cDNAs for stylar transmitting tissue-specific proline-rich proteins in tobacco

Abstract

The pistil of flowers is a specialized organ which contains the female gametophytes and provides the structures necessary for pollination and fertilization. Pollen deposited on the stigmatic surface of a compatible plant germinates a pollen tube which penetrates the stigmatic papillae and grows intercellularly through the style towards the ovules in the ovary. Pollen tube growth is largely restricted to the transmitting tissue in the style. Therefore the stylar transmitting tissue is extremely important for the migration of the pollen cell towards the ovary. We have isolated two related cDNAs, transmitting tissue-specific (TTS)-1 and TTS-2, derived from two proline-rich protein (PRP)-encoding mRNAs that accumulate specifically in the transmitting tissue of tobacco. The deduced PRP sequences share similarities with proline-rich cell wall glycoproteins found in a variety of plants. TTS-1 and TTS-2 mRNAs are induced in very young floral buds, accumulate most abundantly during the later stages of flower development when style elongation is the most rapid, and remain at relatively high levels at anthesis. These mRNAs become undetectable in maturing green fruits. In situ hybridization shows that TTS-1 and TTS-2 mRNA accumulation is restricted to the transmitting tissue of the style. The possible roles that these transmitting tissue-specific PRPs may play in maintaining the structural integrity of the style or in the function of this organ is discussed.

Arabinogalactan-proteins: structure, expression and function

“…Thus, it is likely that this bean PRP is actually a nonclassical AGP. Moreover, the carrot AGP shows a substantial degree of similarity to a set of related tobacco clones, NaPRP4, TTS-1 and TTS-2 [16,18]. The conservation of the number and relative positions of Cys residues in these encoded proteins is also noteworthy.…”

“…To date, few published reports on in situ localization of AGP mRNAs exist [18]. Given that the majority of the antibodies against AGPs apparently recognize more than one AGP family member, such experiments should provide useful gene-specific data.…”

Extensin-like Glycoproteins in the Maize Pollen Tube Wall.

“…HRGPs have long been proposed to play a role in plant reproduction, since AGPs were first discovered in styles (Clarke et al, 1979). More recently, extensin-like genes have been found to be expressed in the transmitting tissue of several species (Baldwin et al, 1992;Goldman et al, 1992;Cheung et al, 1993;Wu et al, 1993;Cheung, 1995). In addition, a pistil-specific PRP was localized to the transmitting tract of tobacco styles (Wang et al, 1993), and an HRGP with characteristics of both extensins and AGPs was isolated from transmitting tissue fluid in N. alata (Lind et al, 1994).…”

“…of extensin-like and PRP genes specifically expressed in pistillate tissues have been identified in several plant species (Baldwin et al, 1992;Chen et al, 1992;Goldman et al, 1992;Cheung et al, 1993;Wu et al, 1993).…”

Class III Pistil-Specific Extensin-Like Proteins from Tobacco Have Characteristics of Arabinogalactan Proteins

“…It has been proposed that these IM components might function in a variety of processes related to pollen tube growth such as nutrition, protection/defense, guidance, and signaling (Sanders and Lord, 1992;Cheung et al, 1995). Biochemical and molecular analyses of secreted proteins found in the IM and their genes or cDNAs led to the identification of several hydroxy-Pro (Hyp)-rich glycoproteins (HRGPs), including arabinogalactan proteins (AGPs), extensin-like glycoproteins, and Pro/ HRGPs (P/HRGPs; Chen et al, 1992;Goldman et al, 1992;Cheung et al, 1993;Wu et al, 1993;Lind et al, 1994;Du et al, 1996;Sommer-Knudsen et al, 1996). The biological function of most of these pistil-specific glycoproteins has not yet been established, although some involvement in pollen tube growth has been reported for some of these proteins (Cheung et al, 1995;Lind et al, 1996;Sommer-Knudsen et al, 1998b).…”