© 2005 Heron Publishing—Victoria, Canada
Water stress-responsive genes in loblolly pine (Pinus taeda) roots identified by analyses of expressed sequence tag libraries
W. Walter Lorenz (1), Feng Sun (2), Chun Liang (2), Dmitri Kolychev (2), Haiming Wang (2), Xin Zhao (2), Marie-Michele Cordonnier-Pratt (2), Lee H. Pratt (2) and Jeffrey F. D. Dean (1, 3)
1. Daniel B. Warnell School of Forest Resources, University of Georgia, Athens, GA 30602, USA / 2. Department of Plant Biology, University of Georgia, Athens, GA 30602, USA / 3. Corresponding author (jeffdean@uga.edu) / Received January 10, 2005; accepted May 3, 2005; published online October 3, 2005
Summary
Drought stress is the principal cause of seedling mortality in pine forests of the southeastern United States and in many
other forested regions around the globe. As part of a larger effort to discover loblolly pine genes, this study subjected
rooted cuttings of three unrelated pine genotypes to three watering regimens. Expressed sequence tags (ESTs) were obtained
from both the 3' and 5' ends of 12,918 randomly selected cDNAs generated from root tissues. These ESTs were clustered to identify
6,765 unique transcripts (UniScripts) derived from 6,202 putative unique genes (UniGenes-S). Tentative annotations were assigned
on the basis of BLASTX comparisons to the Protein Information Resource Nonredundant Reference (PIR-NREF) database. Expression
levels of 42 UniScripts varied with high statistical significance with respect to treatment. Many of them resembled gene products
shown to be important for drought tolerance in other species, including dehydrins, endochitinases, cytochrome P450 enzymes,
pathogenesis-related proteins and various late-embryogenesis abundant (LEA) gene products. Similarly, expression levels of
110 UniScripts varied with high statistical significance among genotypes, indicating that gene expression patterns in this
species are much more dependent on genotype than on treatment. Most of the water stress-induced pine UniScripts that appeared
to encode products resembling drought tolerance factors in other species were most highly induced in a single genotype, suggesting
that particularly useful adaptive alleles for drought tolerance might exist within the collection of cDNAs characterized from
this genotype. Mining and visualizing the complete data set, as well as downloading of both EST and UniScript contig sequences,
are possible using MAGIC Gene Discovery at http://fungen.org/genediscovery/.
Keywords:
conifer, drought tolerance, EST, functional genomics, R statistic, transcriptional profiling.
