Switching the direction of stem gravitropism by altering two amino acids in AtLAZY1 (Plant Phys)

In a fascinating twist to the gravitropism story, Yoshihara and Spalding have managed to make a plant with shoots that don’t ignore gravity, but actually respond in the entirely inappropriate away. The LAZY genes were first identified from a rice mutant with a decreased response to gravity. In Arabidopsis there are five genes in this family, and most share several conserved sequences of unknown function. Using atlazy1 mutants, the authors tested proteins with mutations in each of the conserved region and found one that showed a flipped gravitropism, with shoots that selectively grow down (positive gravitropism) rather than up (negative gravitropism). Interestingly, the mutant plants show a normal response to asymmetric auxin, but in the mutant the auxin gradient is flipped relative to in wild-type plants. As yet the connection between AtLAZY1 and the auxin gradient is still being worked out. (Summary by Mary Williams)  Plant Physiol.  10.1104/pp.19.01144