PHYTOCHROME-INTERACTING FACTOR 7 and RELATIVE OF EARLY FLOWERING 6 act in shade avoidance memory in Arabidopsis

Area of Science:

• Plant Biology
• Epigenetics
• Molecular Biology

Background:

• Shade avoidance is crucial for plants competing for light.
• The existence of a priming mechanism for shade avoidance responses was previously unknown.

Purpose of the Study:

• To investigate if plants possess a memory of prior shade exposure.
• To identify the molecular mechanisms underlying this shade avoidance memory.

Main Methods:

• Utilized the shade-intolerant plant Arabidopsis.
• Employed RNA-sequencing to analyze gene expression changes.
• Investigated the roles of PHYTOCHROME-INTERACTING FACTOR 7 (PIF7) and RELATIVE OF EARLY FLOWERING 6 (REF6).
• Analyzed H3K27me3 enrichment to understand epigenetic modifications.

Main Results:

• Arabidopsis demonstrated memory of a first shade event, leading to more efficient hypocotyl elongation upon subsequent shade.
• PIF7 and REF6 were identified as essential for this shade avoidance memory.
• Mutants lacking PIF7 or REF6 showed impaired induction of shade-memory-related genes.
• Priming shade treatment led to PIF7 accumulation, recruiting REF6 to demethylate H3K27me3 on specific genes, priming them for transcription.

Conclusions:

• Transcriptional memory, mediated by epigenetic modifications, enables plants to remember past shade conditions.
• This memory results in enhanced growth responses to recurring shade, optimizing light acquisition.