title: Identification and characterization of an expansin gene AsEXP1 associated with heat tolerance in C3 Agrostis grass species.
abstract: Plant tolerance of heat stress involves various changes at physiological and molecular levels. The objective of this study was to examine the expression of a gene encoding expansin protein in relation to heat tolerance in two C(3) grass species and genotypes differing in heat tolerance. Heat-tolerant, thermal Agrostis scabra, adapted to high temperatures in geothermal areas in Yellowstone National Park, was subjected to 20 degrees C (control) or 40 degrees C (heat stress) for 7 d in a growth chamber. Differential display analysis identified that a gene, AsEXP1, encoding an expansin protein, was strongly up-regulated in leaves exposed to heat stress in thermal A. scabra. Virtual northern hybridization and RT-PCR confirmed that AsEXP1 was a heat-inducible gene in leaves. The expression of AsEXP1 was induced at 1 h of plant exposure to heat stress and reached the highest level of expression at 4 h of treatment. A 1.3 kb full-length cDNA of AsEXP1 was isolated, which encodes a 251 amino acid protein. Two ecotypes of thermal A. scabra and 10 genotypes of Agrostis stolonifera (creeping bentgrass), a widely used turfgrass species in cool climatic regions, varying in the level of heat tolerance, were exposed to 40 degrees C for 7 d to examine the level of AsEXP1 expression in relation to heat tolerance. Genetic variation in heat tolerance was evaluated by measuring cell membrane stability, photochemical efficiency, and leaf growth. RT-PCR analysis revealed that the level of AsEXP1 in different genotypes was positively correlated with the level of heat tolerance in both grass species. The results first identified a heat-related expansin gene in grass species and suggest that AsEXP1 may be useful as a molecular marker to select for heat-tolerant grass germplasm.
authors.affiliation: Beijing Forestry University, Beijing 100083, China.
authors.forename: Jichen
authors.initials: J
authors.lastname: Xu
authors.forename: Jiang
authors.initials: J
authors.lastname: Tian
authors.forename: Faith C
authors.initials: FC
authors.lastname: Belanger
authors.forename: Bingru
authors.initials: B
authors.lastname: Huang
mesh_terms: D000222:Adaptation, Physiological; D031703:Agrostis / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D015152:Blotting, Northern; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
chemical_list: D010940:Plant Proteins; C095825:expansin protein, plant