PIF4 and HOOKLESS1 Impinge on Common Transcriptome and Isoform Regulation in Thermomorphogenesis

Area of Science:

• Plant Biology
• Molecular Biology
• Genetics

Background:

• High temperatures induce thermomorphogenesis, involving hypocotyl elongation and leaf hyponasty.
• PHYTOCHROME-INTERACTING FACTOR4 (PIF4) is a known regulator, but HOOKLESS1 (HLS1)'s role and mechanisms are unclear.

Purpose of the Study:

• To elucidate the molecular mechanisms of HLS1 in thermomorphogenesis.
• To investigate the interplay between HLS1, PIF4, and gene regulation under heat stress.

Main Methods:

• Comparative analysis of differential gene expression (DEG) and differential alternative splicing (DAS) in wild-type and mutant plants.
• Protein-protein interaction studies to identify regulatory modules.
• Analysis of spliceosome-defective mutants' response to high temperature.

Main Results:

• HLS1 and PIF4 coregulate numerous genes involved in growth and defense.
• HLS1 interacts with PIF4, forming a regulatory module; 27.7% of coregulated genes are PIF4 direct targets.
• Over half of high-temperature-induced alternative splicing events depend on HLS1 and PIF4, and are crucial for thermomorphogenesis.
• DEG and DASGs regulated by HLS1/PIF4 show minimal overlap, indicating distinct regulatory pathways.

Conclusions:

• The HLS1-PIF4 module is a key regulator of thermomorphogenesis.
• This module precisely controls both transcriptional and post-transcriptional (alternative splicing) processes.
• High temperature employs distinct transcriptional and post-transcriptional strategies orchestrated by the HLS1-PIF4 module.