31002:

The lipid transfer protein gene family and its role in plant response to drought stress.

Authors:	Smart, Lawrence, B.(A)Cameron, Kimberly, D.(A)Nall, Nicole, M.(A)
Affiliations:	(A): Faculty of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry
Presenter:	Smart, Lawrence B., lbsmart@syr.edu

Resistance to water loss from the leaf is provided by cells in the epidermis, including the pavement cells, which produce the cuticle, and the stomates, which regulate stomatal aperture to conserve water. We are interested in the process of differentiation of guard cells and pavement cells and how they respond to drought stress. We have isolated cDNAs that display predominant expression in guard cells of Nicotiana glauca by differential screening of a guard cell cDNA library. The majority of the clones isolated encode lipid transfer protein (LTP) and northern analysis indicates that LTP gene expression is induced under drought stress. It is thought that LTP plays a role in the transport of fatty acids through the aqueous cell wall environment in the process of cuticle deposition. The induction of LTP genes under drought stress supports this proposed role for LTP, since cuticle deposition increases in response to drought stress. We will further test this hypothesis by overexpressing LTP in transgenic hybrid poplar and measuring changes in cuticle deposition. Southern analysis of the N. glauca LTP gene family revealed that the LTP genes expressed in guard cells are part of a subfamily of 5-7 highly homologous genes. Many LTP genes have now been sequenced from a wide range of plant species, and LTP is commonly encoded by a multi-gene family. In order to characterize the full LTP gene family of a plant, we used the Arabidopsis thaliana LTP1 and LTP2 sequences as query sequences in searching dbEST and GenBank. We identified dozens of homologous Arabidopsis ESTs and genomic sequences and sorted them into 9 groups, which include LTP1 and LTP2 and 7 additional genes (LTP3-LTP9). We obtained and sequenced representative EST cDNAs for each of the 6 additional unique LTP sequences present in dbEST from the ABRC. LTP9 was identified in the Arabidopsis genomic sequence, but was not found in the EST database. Further analysis of the Arabidopsis genomic sequence revealed that LTP1 and LTP2 are closely linked to each other, as are LTP3 and LTP8, suggesting that they arose from relatively recent duplication events. Phylogenetic analysis and patterns of gene expression of the complete Arabidopsis LTP gene family will be presented. This work was supported by a grant from the McIntire-Stennis Program of the USDA.