Os03g0323200

• The rice gene Os03g0323200 was reported as OsCHLH in 2003. The OsCHLH gene could encode a protein of 1,388 amino acids with a putative N-terminal chloroplast transit peptide.

Annotated Information

Function

• The OsCHLH gene encodes the largest subunit of the rice Mg-chelatase, a key enzyme in the chlorophyll branch of the tetrapyrrole biosynthetic pathway.

Mutation

• Light microscopic observation of the cross-section of the

chlorina mutant leaf blade did not show any significant change in the size or number of mesophyll cells (data not known). However, TEM analysis revealed that, although there was no change in the number of chloroplasts, their shape in the OschlH mutant was irregular compared with the wild-type chloroplasts (Fig. 8). The knockout mutant did not show dispersal of prolamella bodies and retained the appearance of an etioplast in the continuous light condition. Thylakoid membranes in the mutant chloroplasts also were severely disrupted. The reduction of light harvesting complexes in the thylakoid membrane due to the lack of chlorophyll synthesis may disrupt the thylakoid ultrastructure in the mutant.

• The researchers measured chlorophyll contents in 10-day-old seedlings

(Table 1). In wild-type and the heterozygotic plants, the ratio between chlorophyll a and chlorophyll b was about three (Yamazaki et al. 1999). However, in homozygotic plants, the levels of chlorophylls were very low, indicating lack of chlorophyll biosynthesis.

Labs working on this gene

• National Research Laboratory of Plant Functional Genomics, Division of Molecular and Life Sciences, Pohang University of Science and

Technology (POSTECH), Pohang, 790-784 Republic of Korea

• School of Life Sciences and Biotechonology, Korea University, Seoul, 136-701 Republic of Korea
• Department of Molecular Genetics, National Institute of Agrobiological Resources, Tsukuba, Ibaraki, 305-8602 Japan