The S-Ribonuclease Gene of Petunia hybrida Is Expressed in Nonstylar Tissue, Including Immature Anthers

Abstract

To determine the ability of isolated S-locus promoter sequences to direct organ-specific gene expression, we used microprojectile bombardment to introduce chimeric S-allele/&glucuronidase genes into different tissues of Petunia hybrida for transient expression. Histochemical staining showed that S-locus/B-glucuronidase fusions were expressed in pistil, ovary, and petal tissue. No expression of the chimeric genes was detected in leaves or in mature pollen, either by histochemical staining or by fluorescence assays. RNA blot hybridization confirmed that low levels of S-locus mRNA accumulate in petals and ovaries in vivo. Analysis of the expression pattern of S-locus promoter deletions showed that sequences in the immediate vicinity of the TATA box were sufficient to confer qualitatively correct organ-specific expression of &glucuronidase. To further investigate the potential for S-ribonuclease expression in pollen, we used the polymerase chain reaction to amplify RNA accumulated in developing anthers. These assays demonstrated that mRNA for the S-ribonuclease accumulates to low levels in developing anthers several days prior to corolla opening and pollen anthesis. We discuss these results in light of current models of selfincompatibility.

Cloning a putative self-incompatibility gene from the pollen of the grass Phalaris coerulescens.

“…Dodds et al (1993) reported that the S RNase gene of Nicotiana alata is expressed at low levels in developing pollen, and cDNAs for the S, RNase have been cloned from an anther-derived library. A similar result has recently been reported in Brunia bybrida (Clark and Sims, 1994). In Brassica, mRNA homologous to the stigma S locus gene has been identified by polymerase chain reaction (PCR) in anthers during early microsporogenesis (Guilluy et al, 1991).…”

Role of Petal-Specific Orcinol O-Methyltransferases in the Evolution of Rose Scent

“…Moreover, characterization of the internal structure of the rose petal secretory cell, using GFPfusion proteins targeted to different cellular compartments, indicated a similar general structure to more commonly studied cellular models such as tobacco or onion (Allium cepa) epidermis cells (Boevink et al, 1998;Scott et al, 1999;Brandizzi et al, 2004), providing the possibility of comparative studies of secretory and nonsecretory cell types. Biolistic transformation can be applied to the petals from other plant species (Clark and Sims, 1994;Quattrocchio et al, 1999), and the results presented in this study therefore underline the potential of petal epidermal cells as a secretory cell model system.…”

“…However, because of the dispersed distribution of secretory structures on the organ surface, currently used secretory model systems are not well suited to a combined use of transient expression from gene gun delivered constructs and in vivo imaging techniques. On the other hand, biolistic transformation of petal cells has been limited to approaches such as promoter characterization (Clark and Sims, 1994;Quattrocchio et al, 1999).…”

The S-locus of Nicotiana alata: genomic organization and sequence analysis of two S-RNase alleles

“…In solanaceous plants such as Nicotiana alata, self-incompatibility is controlled by a single genetic locus (S-locus) with many alleles. The only known product of this locus in solanaceous plants is an extracellular glycoprotein with ribonuclease activity (S-RNase) that is expressed at high levels within the mature style [ 1,23 ] and at much lower levels within developing pollen grains [7,11 ]. Expression of S-RNases within the style is necessary for self-incompatibility [20,26], and the ribonuclease activity of the protein is required for rejection of incompatible pollen [15,19].…”

“…Self-incompatibility requires interaction of allelic products of the S-locus from pollen and style and recent evidence has confirmed that S-RNases are indeed stylar products of the S-locus [19,20,26]. The product of the S-locus in pollen is not known and, although S-RNase genes are also expressed in pollen [7,11], mutational studies indicate that the determinants of self-incompatibility in style and pollen are likely to be different. Several approaches are being used in attempts to identify unequivocally the product of the S-locus in pollen.…”