Two genes keep seedlings from poisoning themselves while greening
Zhu H, Li Y, Yang W, Grimm B, Lin R
Plant Signaling
The seedlings sprouting in your garden right now are racing against a self-destruct switch, and this research shows which genetic brakes keep them from producing toxic byproducts as their first leaves turn green.
When a seedling sprouts and starts making chlorophyll to capture sunlight, it also has to make heme, the molecule that carries oxygen and drives other essential chemistry. Making both at once is risky: if the process gets out of balance, plants build up light-reactive molecules that cause cellular damage, sometimes killing the seedling. Researchers found two genes, nicknamed GUN2 and GUN3, that act like traffic controllers, keeping chlorophyll and heme production in sync so young plants can green up safely.
Key Findings
Mutations in GUN2 (heme oxygenase) or GUN3 (phytochromobilin synthase) rescued a light-sensitive mutant from cell death by lowering toxic singlet oxygen levels
GUN2 and GUN3 mutations cause heme buildup that feedback-inhibits an early step in chlorophyll precursor synthesis, reducing protochlorophyllide accumulation
GUN2 and GUN3 physically interact with GUN4, and their mutation reduces levels of GUN4 and GUN5, both required for the magnesium-insertion step of chlorophyll synthesis
chevron_right Technical Summary
Scientists discovered how plants avoid a dangerous chemical pileup while turning sunlight into the machinery of photosynthesis. Two genes, GUN2 and GUN3, act as a checkpoint that balances the production of chlorophyll and heme, preventing seedlings from generating toxic, cell-damaging molecules as they green up.
Abstract Preview
Original paper
GUN2 and GUN3 Coordinate Heme and Chlorophyll Metabolism Thereby Impacting Singlet Oxygen Production and Photooxidative Responses.
Tetrapyrrole biosynthesis is an absolute essential metabolic pathway in plants that predominantly gives rise to chlorophyll, heme, and phytochromobilin. Dysregulation of tetrapyrrole biosynthesis s...
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