DOMAIN OF UNKNOWN FUNCTION581-9 negatively regulates SnRK1 kinase activity

Area of Science:

• Plant molecular biology
• Plant physiology
• Biochemistry

Background:

• Sucrose nonfermenting 1 (SNF1)-related protein kinase 1 (SnRK1) is a crucial energy sensor in plants, regulating transcriptional changes for cellular homeostasis during energy deficit.
• The precise mechanisms controlling SnRK1 activation remain incompletely understood, despite its negative regulation.

Purpose of the Study:

• To investigate the role of the Arabidopsis DOMAIN OF UNKNOWN FUNCTION (DUF581) protein, specifically DUF581-9/FCS-like zinc finger 3, in regulating SnRK1 activity.
• To elucidate the molecular mechanism by which DUF581-9 affects SnRK1 activation and plant response to starvation.

Main Methods:

• Investigated the interaction between DUF581-9 and the catalytic subunit of SnRK1 (KIN10) in Arabidopsis.
• Assessed SnRK1 activity, T-loop phosphorylation, and KIN10 auto-phosphorylation in the presence and absence of DUF581-9.
• Examined the effect of DUF581-9 overexpression on plant adaptation to starvation and its protein turnover rate.

Main Results:

• DUF581-9 directly binds to KIN10, inhibiting SnRK1 activation by preventing geminivirus rep-interacting kinase (GRIK)-dependent T-loop phosphorylation.
• Overexpression of DUF581-9 in Arabidopsis reduced SnRK1 signaling, impaired adaptation to starvation, and decreased KIN10 phosphorylation.
• DUF581-9 protein undergoes rapid proteasomal degradation during starvation, releasing inhibition and facilitating SnRK1 activation.

Conclusions:

• DUF581-9 acts as a negative regulator of SnRK1 activity under energy-sufficient conditions.
• The rapid turnover of DUF581-9 during energy deficit provides a swift mechanism for SnRK1 activation, independent of de novo protein synthesis, aiding plant adaptation.