Biology subjects

Whitewoods, C. D.

Publications and source records attributed to Whitewoods, C. D..

3 recordsLinked to original sources

bioRxiv2026

The chloroplast-localised transporter RETICULATA controls palisade mesophyll cell division and expansion

Plant leaves contain extensive intercellular air spaces, which contribute to photosynthetic capacity and water use efficiency in different environments. Despite this importance, the developmental mechanisms that control leaf air space patterning are poorly understood. For over 20 years it has been known that plants with disrupted chloroplast biogenesis and metabolism have increased intercellular air spaces, but the underlying molecular mechanism is unknown. Here, we characterise leaf air space morphogenesis in mutants of the chloroplast amino acid transporter RETICULATA (RE), which has enlarged air spaces. We show that the reticulata-6 (re-6) loss of function mutant exhibits increased air space expansion specifically in the palisade, and not the spongy, mesophyll. We also show that RE does not regulate air space patterning via programmed cell death, via a change in stomatal density or a change in cell identity of the mesophyll tissue. Instead, we quantify mesophyll cell morphology and division rates to show that RE acts by promoting early palisade cell division and suppressing later cell expansion. Overall, we show that RE specifically regulated palisade mesophyll morphogenesis and air space patterning and hypothesise that chloroplasts may act to regulate air space patterning in the palisade mesophyll in response to light.

plant biology↗

bioRxiv2025

Brassinosteroid controls leaf air space patterning non-cell autonomously by promoting epidermal growth

Plant leaves contain a complex network of intercellular air spaces, which enhance gas exchange and allow efficient photosynthesis. However, despite their importance, how leaf air spaces are patterned is poorly understood. It has been proposed for almost a century that air spaces form by faster-growing epidermal tissue pulling slower-growing mesophyll cells apart, but this has never been tested. Here we characterise air space morphogenesis throughout the entirety of leaf development in the first leaf of A. thaliana and show that the plant hormone brassinosteroid (BR) is required for air space expansion in the palisade, but not the spongy, mesophyll. We also show that epidermal brassinosteroid perception is sufficient to promote air space expansion in the palisade non cell-autonomously and propose that this non cell-autonomous effect is due to altered epidermal growth. To test if epidermal growth affects air space patterning we reduce growth specifically in the epidermis using inducible expression of the growth repressor BIG BROTHER and show that an epidermal growth restriction reduces air space expansion in the palisade mesophyll. Overall, we propose that brassinosteroid signalling promotes growth in the epidermis to pattern air spaces in the palisade mesophyll. Summary statementUp to 70% of leaf volume is intercellular air space. This work shows that the plant hormone brassinosteroid acts in the epidermis to promote air space morphogenesis non-cell autonomously.

plant biology↗

bioRxiv2023

Genetic control of cell layer interactions in plants via tissue mechanics

Plant development depends on coordination of growth between different cell layers. Coordination may be mediated by molecular signalling or mechanical connectivity between cells, but evidence for genetic control via direct mechanics has been lacking. We show that a brassinosteroid-deficient dwarf mutant of the aquatic plant Utricularia gibba has twisted internal tissue, likely caused by a mechanical constraint from a slow-growing epidermis creating tissue stresses. This conclusion is supported by showing that inhibition of brassinosteroid action in an Arabidopsis mutant compromised for cell adhesion, enhances epidermal crack formation, an indicator of increased tissue tension. Thus, genes driving brassinosteroid synthesis can promote growth of internal tissue by reducing mechanical epidermal constraint, showing that tissue mechanics plays a key role in coordinating growth between cell layers. One-Sentence SummaryInternal twists in a mutant carnivorous plant reveal how genes control growth via tissue mechanics.

plant biology↗