Chloride transport and homeostasis in plants.

The micronutrient chloride (Cl) plays key roles in plant physiology, from photosystem II and vacuolar ATPase activity to osmoregulation, turgor maintenance and drought resilience, while also posing toxicity risks at high concentrations. This review examines Cl uptake, transport and homeostasis, focussing on adaptations balancing its dual roles as a nutrient and toxicant. Key transporters, including NPF, SLAH, ALMT, CLC and CCC families, mediate Cl fluxes to maintain ionic balance and prevent toxicity.

Potassium extrusion by plant cells: evolution from an emergency valve to a driver of long-distance transport.

The ability to accumulate nutrients is a hallmark for living creatures and plants evolved highly effective nutrient transport systems, especially for the uptake of potassium (K). However, plants also developed mechanisms that enable the rapid extrusion of K in combination with anions. The combined release of K and anions is probably an ancient extrusion system, as it is found in the Characeae that are closely related to land plants.

Guard cells count the number of unitary cytosolic Ca signals to regulate stomatal dynamics.

Transient stimulus-specific increases in the cytosolic Ca concentration ("calcium signatures") of guard cells have been proposed to regulate the opening and closure of stomatal pores on plant leaves. However, the mechanism by which these Ca signatures are generated and translated into stomatal movement is still largely unresolved. We used a light-gated, Ca-permeable variant of ChannelRhodopsin 2 (ChR2-XXM2.

Light-gated channelrhodopsin sparks proton-induced calcium release in guard cells.

Although there has been long-standing recognition that stimuli-induced cytosolic pH alterations coincide with changes in calcium ion (Ca) levels, the interdependence between protons (H) and Ca remains poorly understood. We addressed this topic using the light-gated channelrhodopsin KCR2 from the pseudofungus , which operates as a H conductive, Ca impermeable ion channel on the plasma membrane of plant cells. Light activation of KCR2 in guard cells evokes a transient cytoplasmic acidification that sparks Ca release from the endoplasmic reticulum.