Abstract
Red light promotes germination after activating phytochrome phyB, which destabilizes the germination repressor PIF1. Early upon seed imbibition, canopy light, unfavorable for photosynthesis, represses germination by stabilizing PIF1 after inactivating phyB. Paradoxically, later upon imbibition, canopy light stimulates germination after activating phytochrome phyA. phyA-mediated germination is poorly understood and, intriguingly, is inefficient, compared to phyB-mediated germination, raising the question of its physiological significance. A genetic screen identified polyamine uptake transporter 2 (put2) mutants that overaccumulate polyamines, a class of antioxidant polycations implicated in numerous cellular functions, which we found promote phyA-mediated germination. In WT seeds, our data suggest that canopy light represses polyamines accumulation through PIF1 while red light promotes polyamines accumulation. We show that canopy light also downregulates PIF1 levels, through phyA; however, PIF1 reaccumulates rapidly, which limits phyA-mediated germination. High polyamines levels in decaying seeds bypass PIF1 repression of germination and stimulate phyA-mediated germination, suggesting an adaptive mechanism promoting survival when viability is compromised.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
1-Pyrroline-5-Carboxylate Dehydrogenase / genetics*
-
1-Pyrroline-5-Carboxylate Dehydrogenase / metabolism
-
Amino Acid Transport Systems / genetics*
-
Amino Acid Transport Systems / metabolism
-
Arabidopsis / growth & development*
-
Arabidopsis / metabolism
-
Arabidopsis Proteins / genetics
-
Arabidopsis Proteins / metabolism*
-
Basic Helix-Loop-Helix Transcription Factors / metabolism*
-
Down-Regulation
-
Germination
-
Light
-
Mutation
-
Phytochrome A / metabolism*
-
Polyamines / metabolism
-
Saccharomyces cerevisiae Proteins / genetics*
-
Saccharomyces cerevisiae Proteins / metabolism
Substances
-
Amino Acid Transport Systems
-
Arabidopsis Proteins
-
Basic Helix-Loop-Helix Transcription Factors
-
PIF1 protein, Arabidopsis
-
Phytochrome A
-
Polyamines
-
Saccharomyces cerevisiae Proteins
-
1-Pyrroline-5-Carboxylate Dehydrogenase
-
PUT2 protein, S cerevisiae
Grants and funding
This work was supported by grants from the Swiss National Science Foundation and by the State of Geneva (
http://www.snf.ch) (31003A_152660) to LLM, and project No. RO0418 (Sustainable Systems and Technologies, Improving Crop Production for Higher Quality of Production of Food, Feed, and Raw Materials, under Conditions of Changing Climate funded by Ministry of Agriculture, Czech Republic,
http://eagri.cz) to PT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.