Ca2+ signature-dependent control of auxin sensitivity in Arabidopsis

Song, H.; Baudon, A.; Freund, M.; Randuch, M.; Pencik, A.; Ondrej, N.; He, Z.; Kaufmann, K.; Gilliham, M.; Friml, J.; Hedrich, R.; Huang, S.

doi:10.1101/2025.10.04.680446

bioRxiv · 10.1101/2025.10.04.680446

Ca2+ signature-dependent control of auxin sensitivity in Arabidopsis

Song, H.·Baudon, A.·Freund, M.·Randuch, M.·Pencik, A.·Ondrej, N.·He, Z.·Kaufmann, K.·Gilliham, M.·Friml, J.·Hedrich, R.·Huang, S.

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Abstract

Plants must continually balance growth with arrest, especially under stress. Auxin signaling acts as a central regulatory hub in this process, yet the mechanisms that dynamically tune early auxin signalling in real time remain unknown. Here, we used the light-gated, Ca2+-permeable Channelrhodopsin 2 variant XXM2.0 to optogenetically impose defined Ca2+ signatures on Arabidopsis root cells. Repetitive light activation triggered cytosolic Ca2+ signals that in turn suppressed auxin-induced membrane depolarization and Ca2+ transients. Moreover, prolonged optogenetic Ca2+ stimulation affects auxin-responsive transcriptional reprogramming. As phenotypic output, reversible inhibition of root growth by suppressing cell division and elongation was observed. We further identify a candidate CaM7-CNGC14 module that likely mediates Ca2+-dependent gating of early auxin signalling. Our study thus introduces a synthetic biology approach to decompose calcium-auxin crosstalk in plant cells, and demonstrates that optogenetically imposed cytosolic Ca2+ signals act as dynamic regulators of auxin susceptibility in roots.

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Song, H., Baudon, A., Freund, M., Randuch, M., Pencik, A., Ondrej, N., He, Z., Kaufmann, K., Gilliham, M., Friml, J., Hedrich, R., Huang, S.. 2025-10-05. Ca2+ signature-dependent control of auxin sensitivity in Arabidopsis. https://doi.org/10.1101/2025.10.04.680446

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