Nucleotide sequence of two anther-specific cDNAs from sunflower (Helianthus annuus L.)

Abstract

We have recently isolated and characterized several flower-specific clones from a sunflower cDNA library [ 1]. Two of these clones, SF2 and SF18, were shown to hybridize exclusively to RNA from anthers in the late developmental stages (none of the two RNA species is detected in anthers from a closed sunflower inflorescence). The two mRNAs, which are abundant RNAs in anthers from male-fertile plants, are barely detectable in anthers from male-sterile plants. In situ hybridization studies using the labeled SF2 cDNA clone as probe have shown that the SF2 mRNA is present only in the epidermal anther cells (Evrard et al., submitted). The lack of crosshybridization between the two cDNAs suggested that the SF2 and SF18 mRNAs code for different proteins.We describe here the nucleotide sequence of the two cDNAs SF2 and SF18. The sequence analysis revealed a size of 653 bp for SF2 cDNA and 656 bp for SF18 cDNA (Fig. 1); this is a little smaller than that of the corresponding mRNAs estimated in northern experiments (800 nucleotides for SF2 and 750 nucleotides for SF18) and indicates that the two cDNAs are incomplete. Translation of the cDNA sequence of SF2 revealed an open reading frame starting with a methionine and extending over 121 amino acids. That translation must start at this specific methionine residue in vivo has recently been confirmed by the study of the corresponding gene (C. Domon, unpublished). SF18 cDNA carries a 161 amino acid-long reading frame, which is incomplete at the amino terminus. The first 8 amino acids of this incomplete SF18 reading frame are also found in the amino terminal region of SF2 (only one valine substituting for a leucine). In SF2, this region carries a typical signal peptide sequence (21 amino acids, 16 of which are hydrophobic).Not only are the SF2 and SF18 mRNAs similar in size, they also share short segments of significant sequence homology: one of these is found in the region coding for the signal peptide (where 25 out of 28 nucleotides are identical); another one is found in the untranslated 3' region which contains the polyadenylation site (AATAAA) and a short poly(A) stretch (21 A residues in SF2 and 18 A residues in SF18). This region is considered to be involved in mRNA stability [2].Although no additional sequence similarity can be detected in the SF2 and SF18 polypeptides (except for the signal peptide sequence), they share some features suggesting that they are functionally related. One of these features is a pattern of 7 cysteine residues with a nearly identical spacing in the amino moiety of the two mature polypeptides. This 'cysteine domain' (Fig. 2A), is alsoxich in charged amino acids (35 ~o in SF2 andThe nucleotide sequence data reported will appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession numbers X53374 (SF2) and X53375 (SF18).

Ha-DEF1, a sunflower defensin, induces cell death in Orobanche parasitic plants

“…2). HaDef1 expression was only detected in roots and mature leaves, with a higher expression rate in the subterranean organ, whereas SD2 and SF18 were only expressed in the inXorescences as already reported (Domon et al 1990;Urdangarin et al 2000). In accordance with these organ-speciWc expression patterns, HaDef1 was found to be up-regulated in sunXower roots in response to O. cumana (Letousey et al 2007), while SD2 and SF18 transcripts were not detected (data not shown).…”

“…The SF18 and SD2 genes exhibit a preferential anther and Xower expression pattern, respectively (Domon et al 1990;Urdangarin et al 2000). HaDef1, originally named def.…”

Molecular characterization of a gene encoding a cysteine-rich protein preferentially expressed in anthers of Lycopersicon esculentum

“…While the TomA5B protein has no other amino acid similarity to any of these proteins, the 108 protein shares 49~o, 36~o and 33~o identity with fi/1, A9 from B. napus, and A9 from A. thaliana, respectively. This cysteine pattern is not found in other stamen-specific genes that are cysteine rich, for example; LAT52 [37], SF2 and SF18 [6] or tap1 [26].…”

Anther-specific, developmentally regulated expression of genes encoding a new class of proline-rich proteins in sunflower

“…In addition, the comparison of the SF2 protein with proline-rich proteins not located in the cell wall, such as the prolamine storage proteins (for a review, see [23]), or with proteins whose cellular location is unclear, such as the soybean nodulin-75 [ 10], did not reveal any sequence similarity. The same observations were made for the protein sequence deduced from another anther-specific cDNA, which was called SF18 and which also has a high proline content [8]. In addition, the protein sequence deduced from the partial sequence of a third antherspecific cDNA (SF19) also revealed a high proline content.…”

“…Interestingly, the protein sequence deduced from the nucleotide sequences of the cDNA clones SF18 [8] also shows a high percentage of proline but is different from that of SF2 and SF19, suggesting that several proline-rich proteins are specifically synthesized during the late stages of anther maturation in sunflower.…”