Main interest of the research group has been in photosynthetic efficiency and its regulation, especially in the mechanism of carbon assimilation. The group has recently focused on: (1) Photosynthetic acclimation to high CO2; (2) Photosynthetic efficiency regulation in main field crops including rice, wheat, and maize; (3) Mechanism of Rubisco activation in vivo.

Principal Investigator: Gen-Yun Chen, Professor. Email: chenggy@sippe.ac.cn
Staff: Xiao-Su Zhang, Reasearch intern; Da-Quan Xu, Professor (emeritus)
Graduate Students: Juan Chen; Jian-Wei Ye
Graduated Student: Dao-Yun Zhang, 2004 (PhD)

RuBP Regeneration Limitation in Rice Leaf Photosynthetic Acclimation to Free-Air CO2 Enrichment (FACE)
Atmospheric CO2 concentration has risen at an accelerating pace since the start of the Industrial Revolution. Before the Industrial Revolution CO2 was stable at about 270 μmol/mol; today CO2 is approximately 38% higher at 380 μmol/mol, and by the middle of this century it is predicted to reach 550 μmol/mol and to surpass 700 μmol/mol by the end of the century. Free-air CO2 enrichment (FACE) technique is a new method to study the effects of elevated CO2 on plants developed in the mid 1980s.
In our previous study it showed that both ribulose-1,5-bisphosphate (RuBP) carboxylation limitation and RuBP regeneration limitation exist simultaneously in rice grown under FACE conditions. In order to understand which is the predominant one in photosynthetic acclimation to elevated CO2 in rice, gas exchange, chlorophyll fluorescence, some biochemical and molecular indexes related to photosynthesis were measured. Compared with those in ambient leaves, the net CO2 assimilation rate, in vivo maximum carboxylation rate and maximum electron transport rate, Rubisco and RuBP contents, the whole chain electron transport and photophosphorylation rates, the mRNA levels of genes petA and petD respectively encoding the cytochrome (Cyt) f and the subunit IV of Cyt b6f complex, and the amount of Cyt f protein were significantly decreased, while 3-phosphoglyceric acid content, light-harvesting complex (LHC) b2 and D1 protein levels, and phosphoribulokinase activity were increased significantly in FACE leaves. Hence, RuBP regeneration limitation is a predominant one, and the decrease in the Cyt f is an important reason of the decreased RuBP regeneration capacity in FACE leaves.

Major Publications:

1. Zhang DY, Chen GY, Gong ZY, Chen J, Yong ZH, Zhu JG, Xu DQ. (2008) Ribulose-1,5-bisphosphate regeneration limitation in rice leaf photosynthetic acclimation to elevated CO2. Plant Science 175: 348-355.

2. Zhang DY, Gong ZY, Ye JW, Wu YX, Mi HL, Chen GY. (2008) Effects of zebra leaf 1-A new variegation mutation on chloroplast development in rice. Journal of Molecular Cell Biology 41: 417-422.

3. Chen Y, Xu DQ. (2007) Changes in leaf photosynthesis of transgenic rice with silenced OsBP-73 gene. Photosynthetica 45: 419-425.

4. Yong ZH, Chen GY, Zhang DY, Chen Y, Chen J, Zhu JG, Xu DQ. (2007) Is photosynthetic acclimation to free-air CO2 enrichment (FACE) related to a strong competition for the assimilatory power between carbon assimilation and nitrogen assimilation in rice leaf? Photosynthetica 45: 85-91.

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