ArabidopsisSTAY-GREEN, Mendel's Green Cotyledon Gene, Encodes Magnesium-Dechelatase.
Pheophytinais an essential component of oxygenic photosynthetic organisms because the primary charge separation between chlorophyllaand pheophytinais the first step in the conversion of light energy. In addition, conversion of chlorophyllato pheophytinais the first step of chlorophyll degradation. Pheophytin is synthesized by extracting magnesium (Mg) from chlorophyll; the enzyme Mg-dechelatase catalyzes this reaction. In this study, we report that Mendel's green cotyledon gene,STAY-GREEN(SGR), encodes Mg-dechelatase. TheArabidopsis thalianagenome has threeSGRgenes,SGR1,SGR2, andSTAY-GREEN LIKE(SGRL). Recombinant SGR1/2 extracted Mg from chlorophyllabut had very low or no activity against chlorophyllidea; by contrast, SGRL had higher dechelating activity against chlorophyllideacompared with chlorophyllaAll SGRs could not extract Mg from chlorophyllbEnzymatic experiments using the photosystem and light-harvesting complexes showed that SGR extracts Mg not only from free chlorophyll but also from chlorophyll in the chlorophyll-protein complexes. Furthermore, most of the chlorophyll and chlorophyll binding proteins disappeared when SGR was transiently expressed by a chemical induction system. Thus, SGR is not only involved in chlorophyll degradation but also contributes to photosystem degradation.
Institute of Low Temperature Science, Hokkaido University, Kita-ku, Sapporo 060-0819, Japan.
Yousuke
Y
Shimoda
Institute of Low Temperature Science, Hokkaido University, Kita-ku, Sapporo 060-0819, Japan ito98@lowtem.hokudai.ac.jp.|CREST, Japan Science and Technology Agency, Kita-ku, Sapporo 060-0819, Japan.
Hisashi
H
Ito
Institute of Low Temperature Science, Hokkaido University, Kita-ku, Sapporo 060-0819, Japan.|CREST, Japan Science and Technology Agency, Kita-ku, Sapporo 060-0819, Japan.
Ayumi
A
Tanaka