Os03g0563300

The rice gene Os03g0563300 was reported as Ch19 in 2006.

Annotated Information

Function

• Chl9 genes encode the OsChlI subunits of Mg-chelatase that play an important role in chloroplast development as a modulator of MgProto.

• The chlorophyll synthesis in developing chloroplasts may be coordinated primarily by the levels of Mg-chelatase activity, and whose mutation causes the alteration of leaf color from green to yellowish-green or albino.

• chl9 mutations negatively affect the formation of thylakoid membranes during chloroplast development, meaning that Mg-chelatase activity is closely associated with the development of chloroplast components.

Mutation

• chl9 mutants exhibit a yellowish-green leaf phenotype under normal growth conditions (Fig. 1B). Abnormal leaf color is first observed on the leaves of 2- to 3-week-old seedlings. And the chl9 mutant exhibits its distinctive phenotype throughout development. In addition, the chl9 mutants are viable. To characterize the chlorina phenotypes of chl9 mutants, the researchers first measured their total chlorophyll contents, and found them to be approximately 34% of wild-type Chl levels (Fig. 1D), indicating that the chlorina phenotype results from reduced chlorophyll levels. Underdeveloped thylakoid membranes, poor granum structures and non-dispersed prolamellar bodies were observed in the chloroplasts of chl9 mutant leaves (Fig. 2C, F).

Fig. 1 Characterization of the chl9 mutants. .

Fig. 2 Electron microscopic analysis of wild-type and chl9 mutants. .

• The MgProto(ME) content of chl9 leaves was lower than 31% of its wild-type indica cultivar, IR36 (Fig. 3). These results verify that the missense mutations in ChlI of chl9 result in the reduction of Mg-chelatase activity and thereby cause decreased chlorophyll accumulation in chl9 mutant leaves.

Fig. 2 Electron microscopic analysis of wild-type and chl9 mutants. .

Labs working on this gene

• Department of Plant Science, Seoul National University Seoul 151-921, Republic of Korea