Expression analysis of a gene family in loblolly pine (Pinus taeda L.) induced by water deficit stress.

A cDNA clone (lp3) from loblolly pine induced by water deficit stress (WDS) has been isolated. It is preferentially induced in roots with a constitutive basal level of expression also observed in stems and needles. Northern blot analysis with well irrigated ABA-treated seedlings indicated that the overall accumulation of lp3 transcripts in the roots was lower than that of water deficit-stressed seedlings. However, within roots, lp3 was induced by ABA indicating that the expression of lp3 in roots under WDS conditions was partly mediated by ABA. The lp3 clone is similar to a group of genes called asr (ABA stress and ripening) genes identified in several species. A genomic clone (lp3-1) was identified and its putative protein has the hydrophylicity profile similar to that of lp3 except for two deletions in the 5' region. The genomic Southern and RT-PCR (reverse transcriptase-polymerase chain reaction) analyses indicate that the lp3 gene belongs to a small multigene family of at least four members with a distinct pattern of expression during WDS.