Plant-specific microtubule-associated protein SPIRAL2 is required for anisotropic growth in Arabidopsis.

In diffusely growing plant cells, cortical microtubules play an important role in regulating the direction of cell expansion. Arabidopsis (Arabidopsis thaliana) spiral2 (spr2) mutant is defective in directional cell elongation and exhibits right-handed helical growth in longitudinally expanding organs such as root, hypocotyl, stem, petiole, and petal. The growth of spr2 roots is more sensitive to microtubule-interacting drugs than is wild-type root growth.

Overexpression of a novel small peptide ROTUNDIFOLIA4 decreases cell proliferation and alters leaf shape in Arabidopsis thaliana.

Leaf shape is determined by polar cell expansion and polar cell proliferation along the leaf axes. However, the genes controlling polar cell proliferation during leaf morphogenesis are largely unknown. We identified a dominant mutant of Arabidopsis thaliana, rotundifolia4-1D (rot4-1D), which possessed short leaves and floral organs.