The RNase PD2 gene of almond (Prunus dulcis) represents an evolutionarily distinct class of S-like RNase genes |
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Authors: | Ma R C Oliveira M M |
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Institution: | (1) ITQB/IBET, Quinta do Marques, Aptd.12, 2780 Oeiras, Portugal E-mail: mmolive@itqb.unl.pt; Fax: +351-21-4421161, PT;(2) Dept. Biologia Vegetal, Fac. Ciencias Lisboa, Campo Grande, 1700 Lisboa, Portugal, PT |
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Abstract: | A cDNA for an S-like RNase (RNase PD2) has been isolated from a pistil cDNA library of Prunus dulcis cv. Ferragnés. The cDNA encodes an acidic protein of 226 amino acid residues with a molecular weight of 25 kDa. A potential
N-glycosylation site is present at the N-terminus in RNase PD2. A signal peptide of 23 amino acid residues and a transmembrane
domain are predicted. The two active-site histidines present in enzymes of the T2/S RNase superfamily were detected in RNase
PD2. Its amino acid sequence shows 71.2% similarity to RNS1 of Arabidopsis and RNase T2 of chickpea, respectively. Northern
blotting and RT-PCR analyses indicate that PD2 is expressed predominantly in petals, pistils of open flowers and leaves of
the almond tree. Analyses of shoots cultured in vitro suggested that the expression of RNase PD2 is associated with phosphate
starvation. Southern analysis detected two sequences related to RNase PD2 in the P. dulcis genome. RFLP analysis showed that S-like RNase genes are polymorphic in different almond cultivars. The PD2 gene sequence
was amplified by PCR and two introns were shown to interrupt the coding region. Based on sequence analysis, we have defined
three classes of S-like RNase genes, with the PD2 RNase gene representing a distinct class. The significance of the structural
divergence of S-like RNase genes is further discussed.
Received: 24 January 2000 / Accepted: 17 March 2000 |
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Keywords: | S-like RNase Phosphate starvation Senescence RFLP Almond |
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