Identification of a novel gene, HAABRC5, from Helianthus annuus (Asteraceae) that is upregulated in response to drought, salinity, and abscisic acid.

Using differential display of mRNA transcripts, we obtained a partial cDNA clone, RSC5-U, that is upregulated by exposure to high salinity. A longer cDNA of 812 nucleotides, designated HaABRC5, was then cloned by rapid amplification of cDNA ends. This full-length cDNA contains an open reading frame of 423 nucleotides encoding 141 amino acids, including a "bipartite nuclear targeting sequence." The deduced amino acid sequence had no similarity to known genes in the database. The expression of HaABRC5 was investigated in more detail using quantitative reverse transcriptase-polymerase chain reaction. HaABRC5 is upregulated by drought, high salinity, and exogenous application of abscisic acid (ABA). The promoter sequence of 229 nucleotides, upstream of HaABRC5, was cloned using rapid amplification of genomic ends. Three ABA-responsive elements were found within the HaABRC5 promoter region. Therefore, HaABRC5 is probably an ABA-responsive nuclear protein playing a role in plant stress response.