Survey of gene expression in winter rye during changes in growth temperature, irradiance or excitation pressure

Previous comparisons of winter rye plants (Secale cereale L. cv. Musketeer) grown in a combination of specific temperature (degreesC)/irradiance (mu m ol m(-2) s(-1)) regimes (20/50; 20/250; 20/800; 5/50; 5/250) revealed (1) t hat photosynthetic acclimation to low temperature mimics photosynthetic acc limation to high light because both conditions result in comparable reducti on states of photosystem II (PSII), that is, comparable PSII excitation pre ssure; (2) that the relative redox state of PSII also appears to regulate a specific cold acclimation gene, Wcs19. In order to identify additional gen es regulated differentially by either low temperature, irradiance or excita tion pressure, we initiated a detailed analysis of gene expression. We iden tified and characterized 42 differentially expressed genes from wheat and r ye. Based on their patterns of regulation under the five growth conditions employed, 37 of the cDNAs could be classified into four groups: genes regul ated by PSII excitation pressure, low temperature, growth irradiance and in teraction between growth temperature and irradiance. Partial sequence analy ses revealed that several of these genes encode known chloroplastic protein s such as ELIPs, transketolase, carbonic anhydrase and Mg-chelatase. Howeve r, five of the genes could not be classified unambiguously into any one of these four categories. The implications of these results and the limitation s of the experimental design are discussed in terms of larger-scale genomic studies designed to understand the interactions of multiple abiotic stress es to which a plant may be exposed when examining regulation of gene expres sion.