Inositol 1,4,5-trisphosphate and intracellular Ca²⁺ levels: A local Ca²⁺ signal can induce the production of Ins(1,4,5)P₃ through a Ca²⁺-sensitive phospholipase C. All phospholipases C so far characterized in plants are of the delta type and may be Ca²⁺-sensitive. Unlike in animal systems, the molecular downstream targets of Ins(1,4,5)P₃ in plants are, as of now, not known. However, Ins(1,4,5)P₃ injected into various plant cells results in an increase in cytosolic calcium. An important property of Ins(1,4,5)P₃ signals is that they are rapidly transmitted between neighboring plant cells. When Ins(1,4,5)P₃ was injected into a staminal hair cell, an Ins(1,4,5)P₃ signal could be transmitted to neighboring cells via plasmodesmata prior to calcium-induced plasmodesmata closure. This allows the plant to distribute an Ins(1,4,5)P₃-mediated Ca²⁺ wave throughout a tissue. This finding may be particularly important for an understanding of osmotic stress responses in higher plants, because a transient increase in Ins(1,4,5)P₃ would provide the cells with the capability to rapidly transmit a stress response to its neighbor prior to sealing the affected cells from the rest of the plant. Thus, Ins(1,4,5)P₃ as a second messenger provides a rapid means of vectorial signal propagation and amplification in plants.

Cellular functions of Phosphoinositides

The inositol headgroup

Cellular localization of phosphoinositides

Phosphoinositides as central mediators of plant growth responses

Unique properties of plant phosphoinositide metabolism

Inositol 1,4,5-trisphosphate regulates intracellular Ca²⁺ levels