Phytochrome-interacting factors play shared and distinct roles in regulating shade avoidance responses in Populus...

Area of Science:

• Plant Biology
• Molecular Genetics
• Forest Science

Background:

• Plants adapt growth to light changes, particularly shade, via shade avoidance syndrome (SAS).
• SAS mechanisms are known in model plants but poorly understood in trees.
• Poplar (Populus) is a key model for tree research.

Purpose of the Study:

• Investigate the role of photoreceptors and PIF transcription factors in poplar SAS.
• Characterize the function of eight Populus tomentosa PIF (PtoPIF) genes in shade response.
• Elucidate the molecular pathways regulating SAS in trees.

Main Methods:

• Gene knockout and overexpression in Populus tomentosa.
• Phenotypic analysis under normal and simulated shade conditions.
• Analysis of gene expression, including auxin biosynthetic genes.

Main Results:

• PtophyB1/2 photoreceptors attenuate SAS in poplars.
• PtoPIF gene knockouts partially reduced SAS, while PtoPIF3.1/3.2 overexpression caused constitutive SAS.
• PtoPIF4.1/4.2 showed minor roles in contrast to Arabidopsis PIF4/5.
• PtoPIF3.1/3.2 directly activate PtoYUC8, a key auxin biosynthetic gene, under shade.

Conclusions:

• Poplar PIF genes, particularly PtoPIF3.1/3.2, are crucial regulators of SAS.
• A conserved PIF-YUC-auxin pathway modulates SAS in trees.
• Poplar PIFs exhibit both conserved and divergent functions compared to Arabidopsis PIFs in SAS regulation.