Molecular and structural analyses of a novel temperature stress-induced lipocalin from wheat and Arabidopsis

Two cDNAs corresponding to a novel lipocalin were identified from wheat and Arabidopsis. The two cDNAs designated Tatil for Triticum aestivum L. temperature-induced lipocalin and Attil for Arabidopsis thaliana temperature-induced lipocalin encode polypeptides of 190 and 186 amino acids respectively. Structure analyses indicated the presence of the three structurally conserved regions that characterize lipocalins. Sequence analyses revealed that this novel class of plant lipocalin shares homology with three evolutionarily related lipocalins: the mammalian apolipoprotein D (ApoD), the bacterial lipocalin and the insect Lazarillo. The comparison of the putative tertiary structures of both the human ApoD and the wheat TaTIL suggest that the two proteins differ in membrane attachment and ligand interaction. Northern analyses demonstrated that Tatil and Attil transcripts are upregulated during cold acclimation and heat-shock treatment. The putative functions of this novel class of plant lipocalins during temperature stresses are discussed.