The HOS1-PIF4/5 module controls callus formation in Arabidopsis leaf explants

Area of Science:

• Plant molecular biology
• Plant genetics
• Developmental biology

Background:

• Plant regeneration is vital for genetic manipulation and genome engineering.
• The molecular mechanisms governing *in vitro* plant regeneration require further elucidation.

Purpose of the Study:

• To investigate the role of the HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 1 (HOS1)-PHYTOCHROME INTERACTING FACTOR 4/5 (PIF4/5) module in plant callus formation.
• To understand the molecular basis of auxin-dependent callus development.

Main Methods:

• Analysis of *hos1-3* and *pif4-101 pif5-3* mutant *Arabidopsis* leaf explants.
• Assessment of callus formation and size.
• Investigation of auxin biosynthesis and signaling pathways.

Main Results:

• The HOS1-PIF4/5 module is involved in callus formation.
• Loss-of-function mutations in *HOS1* enhanced callus formation, while mutations in *PIF4/5* reduced it.
• The function of the HOS1-PIF4/5 module is dependent on auxin pathways.

Conclusions:

• The HOS1-PIF4/5 module plays a critical role in regulating auxin-dependent callus formation in *Arabidopsis*.
• This finding contributes to understanding the molecular control of plant regeneration.