Transposase-derived proteins FHY3/FAR1 interact with PHYTOCHROME-INTERACTING FACTOR1 to regulate chlorophyll biosynthesis by modulating HEMB1 during deetiolation in Arabidopsis.
Successful chlorophyll biosynthesis during initial light exposure is critical for plant survival and growth, as excess accumulation of chlorophyll precursors in darkness can cause photooxidative damage to cells. Therefore, efficient mechanisms have evolved to precisely regulate chlorophyll biosynthesis in plants. Here, we identify FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and FAR-RED IMPAIRED RESPONSE1 (FAR1), two transposase-derived transcription factors, as positive regulators of chlorophyll biosynthesis in Arabidopsis thaliana. We show that null mutations in FHY3 and FAR1 cause reduced protochlorophyllide (a precursor of chlorophyll) levels in darkness and less photobleaching in the light. We find that FHY3 directly binds to the promoter and activates expression of HEMB1, which encodes 5-aminolevulinic acid dehydratase in the chlorophyll biosynthetic pathway. We reveal that PHYTOCHROME-INTERACTING FACTOR1 physically interacts with the DNA binding domain of FHY3, thereby partly repressing FHY3/FAR1-activated HEMB1 expression. Strikingly, FHY3 expression is upregulated by white light. In addition, our genetic data indicate that overexpression, severe reduction, or lack of HEMB1 impairs plant growth and development. Together, our findings reveal a crucial role of FHY3/FAR1 in regulating chlorophyll biosynthesis, thus uncovering a new layer of regulation by which light promotes plant dark-light transition in early seedling development.
Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Weijiang
W
Tang
Wanqing
W
Wang
Dongqin
D
Chen
Qiang
Q
Ji
Yanjun
Y
Jing
Haiyang
H
Wang
Rongcheng
R
Lin
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000096:biosynthesis*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010834:Phytochrome / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D036226:Seedlings / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D002734:Chlorophyll; D009687:Nuclear Proteins; D010834:Phytochrome; C120919:FAR1 protein, Arabidopsis; C452847:FHY3 protein, Arabidopsis; C508068:At2g20180 protein, Arabidopsis