Specific expression of an extensin-like gene in the style of Nicotiana alata.

Abstract

cDNAs and corresponding genomic clones encoding a putative proline-rich protein (NaPRP3) were isolated from libraries prepared from Nicotiana alata style mRNA and genomic DNA. The predicted NaPRP3 protein is structurally similar to extensin in containing six copies of the characteristic extensin sequence Ser-Pro4, but differs in being smaller (151 residues compared with greater than 300 residues) and lacking Tyr residues. In contrast to most extensin genes, the NaPRP3 gene is not induced by mechanical wounding, and its expression is restricted to cells of the transmitting tract of the style.

Nucleotide sequence and style-specific expression of a novel proline-rich protein gene from Nicotiana alata

“…The expression of NaPRP4 is restricted to cells of the transmitting tissue of styles and its maximum level of expression is correlated with the elongation and maturation of the style. These expression patterns are similar to those of a style-specific extensin-like protein gene from N. alata (NaPRP3) [ 3 ], suggesting they might have similar functions. Possible functions include maintaining integrity of the transmitting tissue, and providing nutrition or guidance for compatible pollen tubes [3].…”

“…As a part of a broad programme to understand the molecular basis of the fertilisation process in flowering plants, we are investigating the expression and function of proline-rich proteins in styles of Nicotiana alata. We previously reported the characterisation of a style-specific extensin-like gene in N. alata [2,3]. Here, we describe the isolation of another gene (NaPRP4) encoding a novel proline-rich protein.…”

“…One of the PCR fragments obtained encoded a proline-rich protein, which did not contain the amino-acid sequence from which the primers were originally designed. This PCR fragment was used as a probe to screen a cDNA library made from N. alata style RNA as described previously [3]. Four cDNA clones were isolated and the full sequence of one is shown in Fig.…”

“…The size of RNA transcripts is indicated at the right. under conditions described previously [3]. Strong hybridisation of the cDNA probe to the cells of the transmitting tissues was obtained, with no or little hybridisation to stigmatic, cortical or epidermal cells (Fig.…”

“…To examine the expression of the NaPRP4 gene during development of the style, equal amounts of total RNA isolated from styles from developing flowers [small buds (2-3 cm), fully elongated buds (5-6cm), one-day-old and two-day-old flowers] were subjected to northern analysis [3] using the 32p-labelled NaPRP4 cDNA as a probe. The level of hybridising transcript in the style increases from the small bud stage to a maximum in the fully elongated bud stage (Fig.…”