JXB Advance Access originally published online on July 3, 2007
Journal of Experimental Botany 2007 58(11):2717-2731; doi:10.1093/jxb/erm136
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© 2007 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Isolation, characterization, and localization of AgaSGNH cDNA: a new SGNH-motif plant hydrolase specific to Agave americana L. leaf epidermis
Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, E-29071 Málaga, Spain
* To whom correspondence should be addressed. E-mail: heredia{at}uma.es
GDSL and SGNH hydrolases are lipases involved in a wide range of functions, behaving in many cases as bifunctional enzymes. In this work, the isolation and characterization of AgaSGNH, a cDNA encoding a member of the SGNH-hydrolase superfamily from young leaf epidermis of the monocot Agave americana L., is reported. The protein possesses a typical signal peptide at its N-terminus that allows its secretion to the epidermis cell wall, as verified by immunolocalization experiments. In addition, the AgaSGNH sequence contains a His-Leu-Gly-Ala-Glu (HLGAE) motif which is similar to that observed in other plant acyltransferases. Expression levels by northern blot and in situ localization of the corresponding mRNA, as well as the immunolocalization of the protein in Agave young leaves indicate that the protein is specifically present in the epidermal cells. The detailed study performed in different parts of the Agave leaf confirms two aspects: first, the expression of AgaSGNH is limited to the epidermis, and second, the maximum mRNA levels are found in the epidermis of the youngest zones of the leaf which are especially active in cutin biosynthesis. These levels dramatically decrease in the oldest zone of the leaf, where the presence of AgaSGNH mRNA is undetectable, and the biosynthesis of different cuticle components is severely reduced. These data could be compatible with the hypothesis that AgaSGNH could carry out both the hydrolysis and the transfer, from an activated acyl-CoA to a crescent cutin in Agave americana leaves and, therefore, be involved in the still unknown mechanism of plant cutin biosynthesis.
Key words: Agave americana, epidermis, plant cuticle, plant lipases, SGNH-hydrolases
Received 4 March 2007; Revised 17 May 2007 Accepted 25 May 2007