Simultaneous imaging and functional studies reveal a tight correlation between calcium and actin networks

Area of Science:

• Cell Biology
• Plant Science
• Biophysics

Background:

• Tip-growing cells elongate via polarized secretion of cell-wall material.
• Calcium is crucial for regulating cell-wall deposition, but its in vivo targets remain unclear.

Purpose of the Study:

• Investigate intracellular calcium dynamics in tip-growing moss cells.
• Elucidate the mechanistic link between calcium, actin, and polarized cell growth.

Main Methods:

• Utilized a genetically encoded cytosolic FRET probe to visualize calcium dynamics.
• Employed wavelet analysis and signal-sifting for quantitative comparison of calcium behavior.
• Simultaneously imaged cytosolic calcium and actin.

Main Results:

• Observed a fluctuating tipward calcium gradient with oscillatory profiles.
• Suppressed growth correlated with longer calcium oscillation frequencies, indicating feedback.
• High cytosolic calcium promoted actin disassembly, while low calcium promoted assembly at the tip.

Conclusions:

• Tipward calcium gradients are quantitatively linked to actin accumulation in vivo.
• The moss Physcomitrella patens is a powerful model for studying calcium-actin-growth interactions.
• A feedback mechanism exists between calcium gradients and actin organization in tip growth.