Abstract
When rice phytochrome B (phyB) mutants are grown under continuous red light irradiation (Rc), the seedlings display a pale-green phenotype that contain only 20% of chlrophyll as compared with wild type (Nippnbare) seedlings and their chloroplasts are furnished undeveloped thylakoids as well. It suggests that there are phyB-dependent signaling pathways for chloroplast development. To examine the pathways, we tried to isolate factors acting on them through microarray analysis in which comparison of gene expression profiles between phyB and Nipponbare was performed. We hypothesized that reduced expression of the gene for H subunit of Mg chelatase (OsChlH) is the most probable cause for appearance of the pale-green phenotype. To confirm the hypothesis, we exposed Rc to etiolated seedlings grown in the complete darkness for 8 days and observed transitions of OsChlH transcript levels, amounts of chlorophyll precursors and chlorophyll accumulations in the seedlings. Obtained results are consistent with our hypothesis.
