The role of MAPK in the regulation of fungal swelling pressure by ion current

<p> The fungus usually maintains an internal swelling pressure of 500 kPa during growth. However, the fungus inevitably suffers from osmotic stimulation during growth. The organism maintains a transmembrane osmotic gradient by adjusting the swelling pressure to drive cell elongation. Mitogen-activated protein kinase (MAPK) is one of the important signal transduction systems in the organism, which can regulate the osmotic pressure of cells.

The fungus responded rapidly to the hyperosmotic stress, and a short period of depolarization (1-2min) occurred before the recovery of swell pressure (10-60min), followed by continuous hyperpolarization (5-10min). The well-known Australian microbiologist Lew established a research method based on non-damage micro-measurement technology and found that the short-term depolarization is caused by Ca2 + influx, and the continuous hyperpolarization is caused by H + outflow. The osmotic mutant os-1 has a lower swelling pressure than the wild type, and there is no continuous hyperpolarization after the hyperosmotic treatment. There is a significant difference in the ion flow between the two. The Cl- absorption of os-1 increases, and the K + flow is almost unchanged, H + Outflow fell.

The ion flux study and molecular biology experiments show that MAPK can regulate ion transport, activate H + -ATPase and regulate the absorption of K + and Cl-. This study provides evidence for people to understand how cells control ion flow through the action of proteins, and ultimately regulate the cell's swelling pressure to adapt to the osmotic stress in the environment. The regulatory role of Ca2 + in it will be further studied.

Keywords: mitogen-activated protein kinases (MAPK); Turgor; Ion flux; Fungi
References: Lew RR, et al. Eukaryotic cell, 2006, 5,480-487

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