Leiden University Scholarly Publications

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Wei, X. (2024)

Calcium-dependent regulation of auxin transport in plant development

Doctoral Thesis
The plant hormone auxin regulates plant growth and development through polar cell-to-cell transport-generated maxima and minima. PIN FORMED (PIN) auxin efflux carriers determine the direction of this auxin flow through their asymmetric placement on the plasma membrane (PM). In Arabidopsis thaliana (Arabidopsis), the PM-associated protein kinase PINOID (PID) regulates PIN localisation and thereby auxin transport polarity by phosphorylating these carriers in their central cytoplasmic loop. PID in turn interacts with the calmodulin-like protein TOUCH3 (TCH3) in response to elevated cytosolic calcium, which dissociates PID from the PM and inhibits its kinase activity. In this thesis, we show that PID also interacts with 10 other CALMODULIN/CALMODULIN-LIKE proteins, which together with TCH3 form a confined clade in the CaM/CML family. The CaM/CML binding domain in PID was found to map to an amphipathic alpha-helix inserted in the catalytic kinase core. Disruption of this...Show moreThe plant hormone auxin regulates plant growth and development through polar cell-to-cell transport-generated maxima and minima. PIN FORMED (PIN) auxin efflux carriers determine the direction of this auxin flow through their asymmetric placement on the plasma membrane (PM). In Arabidopsis thaliana (Arabidopsis), the PM-associated protein kinase PINOID (PID) regulates PIN localisation and thereby auxin transport polarity by phosphorylating these carriers in their central cytoplasmic loop. PID in turn interacts with the calmodulin-like protein TOUCH3 (TCH3) in response to elevated cytosolic calcium, which dissociates PID from the PM and inhibits its kinase activity. In this thesis, we show that PID also interacts with 10 other CALMODULIN/CALMODULIN-LIKE proteins, which together with TCH3 form a confined clade in the CaM/CML family. The CaM/CML binding domain in PID was found to map to an amphipathic alpha-helix inserted in the catalytic kinase core. Disruption of this alpha-helix did not affect PID kinase activity, but impaired both its PM association and the interaction with the CaM/CMLs, making the kinase “untouchable”. Expression of “untouchable” PID versions in the pid mutant background revealed that proper calcium-CaM/CML-PID signalling is essential to maintain the robust spiral phyllotaxis that is typical for the Arabidopsis inflorescence.Show less
Auxin
PINOID (PID) kinase
Calmodulins/Calmodulin-likes (CaM/CMLs)
CALMODULIN-LIKE 12/TOUCH 3 (CML12/TCH3)
Phyllotaxis
Inflorescence meristem (IM)
Polar auxin transport
Calcium signalling
Arabidopsis thaliana
All authors
Wei, X.
Supervisor
Offringa, R.
Co-supervisor
Hooykaas, P.J.J.
Committee
Meijer, A.H.; Memelink, J.; Balazadeh, S.; Merks, R.M.H.; Geisler, M.; Sprakel, J.H.B.
Qualification
Doctor (dr.)
Awarding Institution
Institute of Biology Leiden (IBL), Faculty of Science, Leiden University
Date
2024-01-11
ISBN (print)
9789464836509

Funding

Sponsorship
China Scholarship Council