The Histone-Modifying Complex PWR/HOS15/HD2C Epigenetically Regulates Cold Tolerance

Area of Science:

• Plant Biology
• Molecular Biology
• Epigenetics

Background:

• Environmental stress, particularly cold, significantly impacts plant growth and crop yields.
• HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE15 (HOS15) is a key component of the CLR4 ubiquitin E3 ligase complex, regulating cold tolerance via epigenetic modifications.
• HOS15 facilitates cold tolerance by degrading HISTONE DEACETYLASE2C (HD2C), altering chromatin structure from repressive to permissive.

Purpose of the Study:

• To investigate the function of POWERDRESS (PWR), a HOS15-binding protein, in the plant cold stress response.
• To elucidate the molecular mechanism by which PWR contributes to cold tolerance in Arabidopsis.

Main Methods:

• Characterization of PWR loss-of-function mutants (pwr) in Arabidopsis thaliana.
• Analysis of cold-regulated (COR) gene expression and freezing sensitivity in wild-type and pwr plants.
• Co-immunoprecipitation assays to study protein-protein interactions between PWR, HOS15, and HD2C.
• Chromatin immunoprecipitation (ChIP) to assess the association of HOS15 and HD2C with COR gene promoters.
• Histone acetylation analysis to evaluate epigenetic modifications.

Main Results:

• pwr mutants exhibit reduced expression of COR genes and increased sensitivity to freezing.
• PWR interacts with HD2C via HOS15, and this interaction is essential for cold-induced HD2C degradation by HOS15.
• The binding of HOS15 and HD2C to COR gene promoters is dependent on PWR.
• Cold-induced histone H3 acetylation at COR gene promoters is significantly reduced in pwr mutants.
• PWR modulates the binding of C-repeat element-binding factor transcription factors to COR gene promoters.

Conclusions:

• The PWR-HOS15-HD2C complex is a critical regulator of COR gene expression and plant freezing tolerance.
• PWR plays an essential role in the epigenetic reprogramming of chromatin structure in response to cold stress.
• Understanding this pathway provides insights into enhancing crop resilience to cold environments.