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bioRxiv · 10.1101/195891

Karrikin-sensing protein KAI2 is a new player in regulating root growth patterns

Swarbreck, S. M.·Guerringue, Y.·Matthus, E.·Jamieson, F. J. C.·Davies, J. M.
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Abstract

Roots form highly complex systems varying in growth direction and branching pattern to forage for nutrients efficiently. Here mutations in the KAI2 (KARRIKIN INSENSITIVE) /{beta}-fold hydrolase and the MAX2 (MORE AXILLARY GROWTH 2) F-box leucine-rich protein, which together perceive karrikins (smoke-derived butenolides), caused alteration in root growth direction (root skewing and waving) of Arabidopsis thaliana. This exaggerated root skewing was independent of endogenous strigolactone perception by the D14 /{beta}-fold hydrolase and MAX2. Thus KAI2/MAX2s regulation of root growth may be through perception of endogenous KAI2-ligands, which have yet to be identified. Degradation targets of the KAI2/MAX2 complex, SMAX1 (SUPPRESSOR OF MAX2-1) and SMXL6,7,8 (SUPPRESSOR OF MAX2-1-LIKE) are also involved in the regulation of root skewing. Genetic data reveal a new potential target for degradation, as mutation in the SKS3 (SKU5 similar) but not the SKU5/SKS17 root plasma membrane glycoprotein suppresses the exaggerated root skewing induced by the lack of MAX2. In Arabidopsis thaliana therefore, the KAI2 karrikin-sensing protein acts to limit root skewing, and we propose a mechanism involving root radial expansion as the mutants gravitropic and mechano-sensing responses remained largely unaffected.

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Swarbreck, S. M., Guerringue, Y., Matthus, E., Jamieson, F. J. C., Davies, J. M.. 2017-09-29. Karrikin-sensing protein KAI2 is a new player in regulating root growth patterns. https://doi.org/10.1101/195891

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