PARENT SESSION
Posters P6B Photosynthetic acclimation: Mechanisms and gene expression. Abstracts (531-578)

Interactions between gene expression and leaf development during acclimation of photosynthesis to irradiance in rice. Erik Murchie^*,1, Stella Hubbart¹, Shaobing Peng², Peter Horton¹, ¹ Department of Molecular Biology and Biotechnology, Sheffield, South Yorkshire, United Kingdom² Crop, Soil and Water Sciences, Manila, Metro Manila, Philippines

ABSTRACT- Rice in tropical agricultural systems can be exposed to a wide range of light levels due to season and climate. The high levels of irradiance seen in the dry season for example result in a significant proportion of photons being excessive for assimilatory requirements and can cause photoinhibition even in well-watered plants. We have used rice as a model plant to study the long-term response of photosynthesis to high irradiance focussing on the composition of the photosynthetic apparatus and leaf morphology. Typical sun / shade differences in chloroplast composition are seen following growth in high compared to low irradiance: higher rates of photosynthesis, higher amounts of Rubisco, cytochrome b/f complex per unit leaf area, but lower levels of light harvesting complex proteins (LHCII) and total chlorophyll. Leaf thickness and total leaf area is also altered. However responses appear more complex when leaf developmental stage is considered. Using a system of transferring plants from low to high light in the laboratory we have studied responses that occur pre-full leaf expansion and post-full leaf expansion: (1) We test the hypothesis that the establishment of a high light leaf anatomy in rice is dependent upon stimuli imposed before the stage of cellular division and expansion within the leaf sheath. (2) Using microarray technology we analyse changes in gene expression occurring as a result of a transfer to high irradiance after full leaf expansion. We examine how the expression of different functional groups of genes, particularly those involved in photosynthesis, stress-responses and cell signalling, change when plants are transferred to high light at specific stages of leaf ageing.

KEY WORDS: photosynthesis, acclimation, development