JXB Advance Access published online on October 10, 2007
Journal of Experimental Botany, doi:10.1093/jxb/erm229
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
© 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.
This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
RESEARCH PAPER |
Identification and characterization of an expansin gene AsEXP1 associated with heat tolerance in C3 Agrostis grass species
1Beijing Forestry University, Beijing 100083, China
2Department of Plant Biology and Pathology, Rutgers, the State University of New Jersey, New Brunswick, NJ 08901, USA
* To whom correspondence should be addressed. E-mail: huang{at}aesop.rutgers.edu
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 C3 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 °C (control) or 40 °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 °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.
Key words: Agrostis scabra, Agrostis stolonifera, high temperature, turfgrass
Received 8 July 2007; Revised 24 August 2007 Accepted 30 August 2007