PARENT SESSION

Symposium S6B Photosynthetic acclimation: Mechanisms and gene expression
Thursday September 2nd, 2004 10:20 AM-12:40 PM Room 210A
Chair: Norio Murata
Co-Chair: Eva-Mari Aro

Environmental stress-induced expression of photosynthesis-related genes. Iwane Suzuki^{*,1, 2}, Yu Kanesaki^{1, 3}, Hiroshi Yamamoto¹, Norio Murata, ¹ Department of Regulation Biology, Okazaki, Japan² Department of Molecular Biomechanics, Okazaki, Japan³ Satellite Venture Business Laboratory, Matsuyama, Japan

ABSTRACT- Photosynthetic organisms are frequently exposed to changes in environmental stress, such as salt, osmotic, cold, heat, oxidative and high light stress, and their photosynthetic efficiency is reduced due to the photodamage of photosynthetic machinery. Recently we found that such environmental stress appears to enhance the extent of photodamage by inhibition of the recovery process. However, these organisms acclimate to the new environment to optimize the photosynthetic efficiency by regulation of the expression of a set of genes. These genes may be involved in the stimulation of repair process from the photodamage. We studied the response to the changes in environment by the genome-wide expression of genes with DNA microarrays in the cyanobacterium Synechocystis sp. PCC6803. The results revealed that some of such stress-inducible genes responded to limited kinds of stress, whereas some others responded to all or many kinds of stress tested. For example, the expression of genes for heat-shock proteins and proteases and the sodB gene for superoxide dismutase was induced by salt, osmotic, oxidative (H₂O₂) and heat-shock, but not by cold stress; The expression of the hli genes for high light-inducible proteins was induced under salt, osmotic, oxidative, high light and cold stress, but not under heat stress; the crhL gene for RNA helicase was induced under salt, osmotic and cold stress, but not under oxidative, heat and high light stress; The expression of the rbp1 gene for RNA-binding protein was induced under cold stress but not under the other kinds of stress. We will discuss the relationship between the stress-inducible gene expression and the acclimation of the photosynthetic organism to environmental stress and also the involvement of stress sensors in the stress-inducible gene expression.

KEY WORDS: Synechocystis, cyanobacteria, DNA microarray, transcriptome