Aldh7B6Encodes a Turgor-Responsive Aldehyde Dehydrogenase Homologue That is Constitutively Expressed in Tortula ruralis Gametophytes

Abstract

The moss Tortula ruralis is an important experimental system for studying the molecular and biochemical mechanisms of vegetative desiccation tolerance in plants. EST searches have identified a cDNA Aldh7B6 encoding a turgor-responsive aldehyde dehydrogenase (ALDH7). ALDH7B6, the 516 amino acid deduced polypeptide, is more than 60% identical to homologues from the protein family ALDH7. ALDH7B6 has a predicted molecular mass of 55.1 kDa and predicted pI of 5.87. RNA blot hybridizations were used to analyze expression of Aldh7B6 in response to desiccation, NaCl, altered light levels, ABA, & UV-C. Aldh7B6 steady-state mRNA transcript levels are unchanged in response to all treatments and the gene is constitutively expressed. We propose three conserved signature sequences for ALDH7 protein members: 1) the PR-box PAPKRGEIVRQIGD (residues 83–96), 2) the catalytic box FAAVGTAGQRCTT (residues 297–309), and the C-box (residues 424–515 of the carboxy terminus). We postulate that ALDH7B6 plays an important role in the detoxification of aldehydes generated in response to desiccation-stress and propose that ALDH7 homologues are more properly described as “stress aldehyde” ALDHs.