Abstract
Photosynthesis is one of the most important determinants of crop productivity. To identify photosynthesis-related genes in rice, we generated Arabidopsis lines that rice full-length cDNAs were expressed. We have used imaging of chlorophyll fluorescence to screen photosynthesis-related mutants. Overexpression of two rice cDNAs (OsLFNR1, OsLFNR2) lead to altered chlorophyll fluorescence both in Arabidopsis and rice. Chlorophyll fluorescence analysis indicated that OsLFNR2 overexpression plant was impaired in linear electron transport and Fd-dependent PSI cyclic electron flow. OsLFNR1 overexpression plants showed growth defect. However, the growth defect was recovered when the plants were grown in nutrient rich medium. When OsLFNR1 overexpression plants were grown in nitrogen limited conditions, they exhibited long roots compared to WT. This suggests that OsLFNR1 overexpression plants have defect in nitrogen assimilation. Expression of OsLFNR genes result in suppression of endogenous FNR genes both in Arabidopsis and rice. From these results we propose that two isoforms of FNR control the balance between the demand for nitrogen assimilation and photosynthetic activity.
