The protein that lets plant cells stretch and grow
Pan J, Sharif R, Fang C, Ma K, Wu X
Plant Signaling
Every time you watch a seedling push through soil, a fruit soften on the vine, or a stressed houseplant bounce back after watering, expansin proteins are doing the physical work of loosening cell walls to make it happen.
Plant cells are wrapped in stiff walls made of cellulose fibers, so to grow bigger those walls have to loosen up without falling apart. Expansins are the proteins that do this: they slip between the fibers and break the hydrogen bonds holding them together, letting the wall stretch like softened taffy. This same trick drives root growth, pollen tubes reaching the egg cell, fruit going soft as it ripens, seeds cracking open, and plants adjusting their walls to survive drought or fend off pests.
Key Findings
Expansins use a two-domain structure (a GH45-like D1 domain and a CBM63-like D2 domain) to loosen cellulose-matrix bonds without breaking down the polymers, unlike enzymes
They drive 'acid growth,' the process where cell walls become more extensible as pH drops, enabling rapid cell expansion
Expansin activity spans the entire plant life cycle, shaping root and shoot architecture, pollen tube growth, fruit softening, seed germination, and stress responses to both abiotic and biotic challenges
chevron_right Technical Summary
A protein family called expansins acts like a molecular crowbar, loosening the bonds inside plant cell walls so cells can stretch and grow. This review pulls together decades of research showing expansins shape everything from root growth to fruit ripening and help plants cope with drought, heat, and pests.
Abstract Preview
Original paper
Expansins: Molecular Mediators of Cell Wall Extensibility in Plant Development and Stress Adaptation.
Expansins are fundamental agents of plant growth and adaptation, enabling cell walls to expand and remodel through unique non-enzymatic mechanisms. This review elucidates the structural biology, ev...
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