Why flower sepals stay smooth: matched growth and stiffness between cell layers
Singh Yadav A, Hong L, Klees PM, Kiss A, Petit M
Plant Signaling
The clean, smooth edge of a leaf or the green sepals cupping a flower bud depend on cell layers growing in step, and when that coordination slips, you get the crinkled, bumpy organs sometimes seen on mutant or oddly grown plants.
Researchers studied a mutant of the small mustard-family plant thale cress in which a leaf-shaping gene switched on in the wrong cell layer. The outer skin of its sepals, the small green leaves that wrap a flower bud, grew in mixed directions and was softer than the layer beneath, so it crumpled like a rug pushed from both ends. Making the outer cells grow lengthwise and stiffen restored a smooth surface, and the crumpling itself helped trigger pointed bumps by concentrating a growth hormone transporter.
Key Findings
Ectopic expression of AS2 on the outer epidermis in the as2-7D mutant caused sepals to buckle early in development.
Buckling resulted from conflicting cell growth directions and unequal stiffness between the two epidermal layers.
Overexpressing the CDK inhibitor KRP1 in as2-7D aligned outer cell growth lengthwise, stiffened the outer epidermis, and restored smooth sepals; buckling also drove PIN1 convergence that initiates pointed outgrowths.
chevron_right Technical Summary
Smooth leaf-like organs stay smooth when cells in both outer layers grow lengthwise and have similar stiffness. When one layer grows in conflicting directions and is softer, the tissue wrinkles and can sprout pointed bumps.
Abstract Preview
Original paper
Growth directions and stiffness across cell layers determine whether tissues stay smooth or buckle.
Nature exhibits organs of various shapes and forms, ranging from smooth to undulated morphologies. How cells coordinate their growth to produce smoothly shaped leaves and leaf-like organs such as s...
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Arabidopsis thaliana, the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed.