[Seminar] Photosynthesis of evergreen trees in wintertime

Title: Photosynthesis of evergreen trees in wintertime

Speaker: Prof. Ryouichi Tanaka

Affiliation: Institute of Low Temperature Science, Hokkaido University

Abstract:

Acquisition of too much energy is harmful for both plants and animals. Animals are supposed to refuse too much food, while plants inevitably acquire energy by absorbing incident light as far as their leaves are green. In winter, evergreen trees are challenged by cold temperature, which substantially decreases cellular metabolism, thus the energy acquisition often surpasses consumption. To cope with this problem, evergreen leaves are able to dissipate energy as heat. Evergreen trees have at least two mechanisms to dissipate energy as heat: one mechanism is known as qE quenching, which is common to all plants, while the other mechanism appears to be specific to evergreen trees, the molecular basis of which is not well understood. We aim to elucidate the energy dissipation mechanisms of evergreen trees by analyzing the photosynthetic responses of yew (Taxus cuspidata) trees throughout a year. We found that the utilization of light energy i.e. the quantum yield of photosystem II (Phi2) linearly correlates with temperature in winter, while it is correlated with light intensity in summer. In our RNAseq analysis, the expression of the ELIP gene encoding a chloroplast protein with unknown function dominates the other genes in winter. We found that ELIP binds a photosynthetic complex in winter. I will discuss a possible regulatory mechanism of photosynthetic energy utilization.

 

Short bio:

R. Tanaka was awarded Ph.D. degree for the work on the analysis of Glutamyl-tRNA reductase (rate-limiting enzyme of chlorophyll biosynthesis), through the Graduate School of Science, in Kyoto University, in 1997. He did a Postdoc in the Institute of Plant Genetics and Crop Plant Research, in Germany, during 1997 and 1998. Having started his Academic career as Assistant Professor at the Hokkaido University, in 1998, R. Tanaka was later promoted to Associate Professor, continuing to work on chlorophyll biosynthesis and photosynthesis.