Generation and analysis of expressed sequence tags from the salt-tolerant mangrove species Avicennia marina (Forsk) Vierh.

Salinization poses an increasingly serious problem in coastal and agricultural areas with negative effects on plant productivity and yield. Avicennia marina is a pantropical mangrove species that can survive in highly saline conditions. As a first step towards the characterization of genes that contribute to combating salinity stress, the construction of a cDNA library of A. marina genes is reported here. Random expressed sequence tag (EST) sequencing of 1,841 clones produced 1,602 quality reads. These clones were classified into functional categories, and blast comparisons revealed that 113 clones were homologous to genes earlier implicated in stress responses, of which the dehydrins are the most predominant in this category. Of the ESTs analyzed, 30% showed homology to previously uncharacterized genes in the public plant databases. Of these 30%, 52 clones were selected for reverse Northern analysis: 26 were shown to be up-regulated and five shown to be down-regulated. The results obtained by reverse Northern analysis were confirmed by Northern analysis for three clones.