Plants are either straight with transverse microtubules (left), or helical thanks to slanted microtubules (right).
Hashimoto/Macmillan
The insights come from studies of Arabidopsis thaliana, which normally grows straight. Hashimoto's team isolated lefty1 and lefty2—which have left-handed helical growth—as suppressors of an existing right-handed helical growth mutant. The new mutants have an identical change in either TUA6 or TUA4—two of the plant's α-tubulin genes.
The change is near the interface with β-tubulin. The disturbed interface may produce the altered angle of microtubules seen in the mutants. Cortical microtubules are normally found running directly across the cells, but the mutant microtubules form in a skewed right-handed helix. This should alter the direction of...