Seed longevity is controlled by metacaspases

Area of Science:

• Plant biology
• Molecular biology
• Biochemistry

Background:

• Seed longevity is essential for survival and relies on maintaining protein homeostasis (proteostasis) during dormancy.
• The precise mechanisms regulating proteostasis in quiescent seeds remain largely unknown.

Purpose of the Study:

• To investigate the role of type-II metacaspase (MCA-II) proteases in seed proteostasis and longevity.
• To elucidate the molecular mechanisms linking MCA-II proteases, CDC48, and protein degradation in seeds.

Main Methods:

• Arabidopsis thaliana genetic mutants lacking all six MCA-II proteases were analyzed.
• Seed proteostasis, CDC48 localization at the endoplasmic reticulum (ER), and lipid droplet dynamics were assessed.
• The interaction between MCA-II proteases, PUX10, and CDC48 was investigated.

Main Results:

• MCA-II mutant seeds exhibited disturbed proteostasis and failed to restrict CDC48 at the ER for misfolded protein clearance.
• Endoplasmic reticulum localization of CDC48 depends on MCA-II-mediated cleavage of the adaptor protein PUX10.
• Loss of MCA-II function led to altered PUX10 levels, partially restoring proteostasis and prolonging seed lifespan.

Conclusions:

• A novel proteolytic module involving MCA-II proteases, PUX10, and CDC48 is identified.
• This module regulates spatiotemporal proteolysis, lipid droplet dynamics, and protein homeostasis, conferring seed longevity.
• Understanding these mechanisms offers potential strategies for enhancing seed storage and viability.