Abstract
A cDNA-amplified fragment length polymorphism (cDNA-AFLP) technique was used for differential screening of genes expressed in longan ( Dimocarpus longan Lour.) flower buds undergoing normal development versus flowering reversion. One cDNA fragment up-regulated during flowering reversion was further cloned by rapid amplification of cDNA ends (RACE) technology. This cDNA consists of 961 nucleotides and encodes an open reading frame (ORF) of 227-amino acid residues. The nucleotides and deduced amino acid sequence were both identical against published chitinases from other species and hence this cDNA was designated as DLchi (GenBank accession No. GU177464). It has a signal peptide and glycoside hydrolase’s domain. The estimated molecular weight was 24.77 kD and the isoelectric point was 5.17. This protein might be grouped as a new member of class II chitinase based on the sequences available and hypothesis discussed. DLchi might be involved in the flower bud abscission observed in longan flowering reversion. Key words: Longan, flowering reversion, chitinase gene, cloning, sequence analysis.
Highlights
Longan (Dimocarpus longan Lour.), a tree with edible fruit, is distributed widely in tropical and subtropical regions
A cDNA-amplified fragment length polymorphism technique was used for differential screening of genes expressed in longan (Dimocarpus longan Lour.) flower buds undergoing normal development versus flowering reversion
The nucleotides and deduced amino acid sequence were both identical against published chitinases from other species and this cDNA was designated as DLchi (GenBank accession No GU177464)
Summary
Longan (Dimocarpus longan Lour.), a tree with edible fruit, is distributed widely in tropical and subtropical regions. When longan flowering reversion occurs, flower buds cease normal development and instead form floral spikes with leaves. Some researchers have shown that chitinase may be involved in abscission of leaves, buds, floral. Campillo and Lewis (1992) reported that basic chitinases accumulated to high levels in abscission zones and they serologically identified a related 33 kD protein in bean anthers and pistils during flower abscission. Four different chitinase transcripts were identified during abscission of citrus leaves and apple fruits (Agusti et al, 2008; Zhou et al, 2008). A wound-inducible class I acidic chitinase gene, win, was reported in young undamaged poplar leaves, while a sharp increase, Xie et al 12505 predominantly in pollen, coincided with anther dehiscence in flowers (Clarke et al, 1994). Abscission involves the dissolving of cell walls or cell separation, so that dehiscence and senescence are similar processes involving cell wall disruption through the action of chitinases (Roberts et al, 2002; Lewis et al, 2006)
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