Brassinosteroid coordinates cell layer interactions in plants via cell wall and tissue mechanics

Area of Science:

• Plant Biology
• Developmental Biology
• Biophysics

Background:

• Coordinated growth between cellular layers is crucial for multicellular organism development.
• The role of genes in modulating mechanical interactions between tissue layers remains largely unexplored.
• Mechanical forces and molecular signaling are potential mediators of inter-layer growth coordination.

Purpose of the Study:

• To investigate how genes controlling brassinosteroid synthesis influence mechanical interactions between plant tissue layers.
• To elucidate the mechanism by which brassinosteroids affect growth coordination, specifically focusing on epidermal constraint.

Main Methods:

• Identification and characterization of a brassinosteroid-deficient dwarf mutant in *Utricularia gibba* exhibiting twisted internal tissue.
• Analysis of a brassinosteroid mutant in *Arabidopsis* to assess epidermal stress through crack formation.
• Investigating the role of brassinosteroids in cell wall remodeling to understand their impact on mechanical properties.

Main Results:

• A brassinosteroid-deficient mutant in *Utricularia gibba* displayed internal tissue twisting, suggesting epidermal mechanical constraint.
• Brassinosteroid deficiency in *Arabidopsis* led to increased epidermal cracking, indicating elevated tissue stress.
• Brassinosteroids appear to reduce mechanical constraint imposed by the epidermis on internal tissues.

Conclusions:

• Genes driving brassinosteroid synthesis promote internal tissue growth by alleviating mechanical epidermal constraint.
• Brassinosteroids likely remodel cell walls, thereby reducing epidermal mechanical resistance.
• This study demonstrates a mechanism by which genes control growth coordination between tissue layers through mechanical regulation.