Polymerization-mediated SRFR1 condensation in upper lateral root cap cells regulates root growth

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Primary root growth is crucial for plants, adapting to environmental factors.
• Lateral root cap (LRC) cells influence meristem size and lateral root initiation.
• Protein condensation is increasingly recognized as a regulator of cellular processes.

Purpose of the Study:

• To identify and characterize a protein condensation mechanism in LRC cells that governs root growth.
• To elucidate the role of SUPPRESSOR of rps4-RLD1 (SRFR1) in root development.
• To investigate how environmental conditions and hormone treatments affect SRFR1 condensation.

Main Methods:

• Identification of an upper LRC-specific protein condensation mechanism involving SRFR1.
• Mutational and biophysical analyses of SRFR1 domains (PANT and IDR1).
• Functional substitution assays using zwitterionic dehydrins.

Main Results:

• SRFR1 condensate formation is driven by the PANT domain and regulated by the zwitterionic IDR1.
• IDR1 acts as a temperature-dependent chaperone, promoting polymerization at low temperatures and preventing aggregation at high temperatures.
• Zwitterionic dehydrins can functionally substitute for IDR1, and altering IDR1's charge impacts SRFR1 condensation and root growth.

Conclusions:

• A novel temperature-adaptive protein condensation mechanism involving SRFR1 regulates root growth.
• The zwitterionic nature of IDR1 is critical for its chaperone activity and physiological function.
• This mechanism of zwitterionic intrinsically disordered regions (IDRs) associated with polymerization domains may be a general principle for preventing aggregation and promoting polymerization under varying temperatures.