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Brassinosteroid controls leaf air space patterning non-cell autonomously by promoting epidermal growth
James M Fitzsimons1, Ana B Rock1, Richard L De Falbe1
1Sainsbury Laboratory, University of Cambridge, 47 Bateman Street, Cambridge CB2 1LR, UK.
Development (Cambridge, England)
|April 24, 2026
Summary
Plant hormone brassinosteroid (BR) is essential for leaf air space expansion. BR signaling in epidermal cells drives palisade mesophyll growth, influencing air space patterning for efficient photosynthesis.
Area of Science:
- Plant Biology
- Developmental Biology
- Plant Physiology
Background:
- Intercellular air spaces in plant leaves are crucial for efficient photosynthesis.
- The developmental mechanisms of leaf air space patterning remain largely unknown.
- A long-standing hypothesis suggests differential growth between epidermal and mesophyll tissues shapes air spaces.
Purpose of the Study:
- To investigate the molecular mechanisms underlying leaf air space morphogenesis in Arabidopsis thaliana.
- To test the role of the plant hormone brassinosteroid (BR) in air space development.
- To determine if epidermal growth influences air space patterning.
Main Methods:
- Characterization of air space development in the first leaf of Arabidopsis thaliana.
- Analysis of brassinosteroid (BR) signaling mutants and manipulation of BR perception.
- Genetic manipulation to specifically alter epidermal growth rates using inducible gene expression.
Main Results:
- Brassinosteroid (BR) is required for air space expansion in the palisade mesophyll, but not spongy mesophyll.
- Epidermal BR perception non-cell-autonomously promotes palisade air space expansion.
- Restricting epidermal growth significantly reduces palisade mesophyll air space expansion.
Conclusions:
- Brassinosteroid (BR) signaling in the epidermis is a key regulator of leaf air space patterning.
- Differential growth between epidermal and mesophyll tissues, mediated by BR, is essential for forming palisade air spaces.
- This study provides experimental evidence supporting and refining the hypothesis of growth-driven air space formation.
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