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First published online November 23, 2005; 10.1104/pp.105.070466 Plant Physiology 139:2017-2028 (2005) © 2005 American Society of Plant Biologists
Identification, Expression, and Evolutionary Analyses of Plant Lipocalins1,[W]Département des Sciences Biologiques (J.-B.F.C., F.O., M.P., J.D., F.S.) and Département d'Informatique (C.C.), Université du Québec à Montréal, Montreal, Quebec, Canada H3C 3P8
Lipocalins are a group of proteins that have been characterized in bacteria, invertebrate, and vertebrate animals. However, very little is known about plant lipocalins. We have previously reported the cloning of the first true plant lipocalins. Here we report the identification and characterization of plant lipocalins and lipocalin-like proteins using an integrated approach of data mining, expression studies, cellular localization, and phylogenetic analyses. Plant lipocalins can be classified into two groups, temperature-induced lipocalins (TILs) and chloroplastic lipocalins (CHLs). In addition, violaxanthin de-epoxidases (VDEs) and zeaxanthin epoxidases (ZEPs) can be classified as lipocalin-like proteins. CHLs, VDEs, and ZEPs possess transit peptides that target them to the chloroplast. On the other hand, TILs do not show any targeting peptide, but localization studies revealed that the proteins are found at the plasma membrane. Expression analyses by quantitative real-time PCR showed that expression of the wheat (Triticum aestivum) lipocalins and lipocalin-like proteins is associated with abiotic stress response and is correlated with the plant's capacity to develop freezing tolerance. In support of this correlation, data mining revealed that lipocalins are present in the desiccation-tolerant red algae Porphyra yezoensis and the cryotolerant marine yeast Debaryomyces hansenii, suggesting a possible association with stress-tolerant organisms. Considering the plant lipocalin properties, tissue specificity, response to temperature stress, and their association with chloroplasts and plasma membranes of green leaves, we hypothesize a protective function of the photosynthetic system against temperature stress. Phylogenetic analyses suggest that TIL lipocalin members in higher plants were probably inherited from a bacterial gene present in a primitive unicellular eukaryote. On the other hand, CHLs, VDEs, and ZEPs may have evolved from a cyanobacterial ancestral gene after the formation of the cyanobacterial endosymbiont from which the chloroplast originated.
1 This work was supported by Genome Canada/Génome Québec and Natural Sciences and Engineering Research Council of Canada. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Fathey Sarhan (sarhan.fathey{at}uqam.ca). [W] The online version of this article contains Web-only data. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.070466. * Corresponding author; e-mail sarhan.fathey{at}uqam.ca; fax 5149874647. Received August 25, 2005; returned for revision October 3, 2005; accepted October 4, 2005. This article has been cited by other articles:
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