AsianScientist (Nov. 4, 2016) – Researchers in Japan have detailed how a gene works to turn tree leaves from green to the warm colors of autumn. Their work is published in The Plant Cell.
In plants, the pigment chlorophyll plays a central role in photosynthesis: the process of converting sunlight to energy. Autumn leaf colors occur when chlorophyll degrades as a normal part of leaf aging. The process of chlorophyll degradation is triggered when an enzyme called Mg-dechelatase extracts magnesium (Mg) from chlorophyll.
In this study, Drs. Yousuke Shimoda, Hisashi Ito, and Ayumi Tanaka at Hokkaido University demonstrated that a gene with known involvement in chlorophyll degradation, called Stay-Green (SGR), encodes for Mg-dechelatase. Stay-Green mutants allow leaves to retain greenness during senescence.
The team transiently induced SGR in fully green leaves of a small flowering plant called thale cress, which caused a reduction in chlorophyll levels. They also incubated chlorophyll with SGR in a test tube, which resulted in the conversion of chlorophyll to pheophytin a—a result that strongly suggests the role of Mg-dechelatase is chlorophyll degradation via SGR.
“It remains unclear whether SGR plays a role via Mg-dechelatase activity in supplying pheophytin a for the process of photosynthesis,” said Ito. “Little is known about the mechanism by which an enzyme extracts a metal ion from an organic compound. Our study may lead to the discovery of novel reaction mechanisms.”
The article can be found at: Shimoda et al. (2016) Arabidopsis STAY-GREEN, Mendel’s Green Cotyledon Gene, Encodes Magnesium-Dechelatase.
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Source: Hokkaido University; Photo: Pexels.
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