Stromule

A stromule (plural: stromules) is a dynamic, tubular extension emanating from a plastid, most commonly a chloroplast, in plant cells. These structures are typically narrow, ranging in diameter from 0.3 to 0.8 μm, and can vary significantly in length, often extending several micrometers. Stromules can connect different plastids within the same cell, facilitating the exchange of molecules and signals between them.

The primary function of stromules is believed to involve intracellular communication and transport between plastids and other cellular compartments, including the nucleus. They are thought to play a role in the distribution of proteins, metabolites, and genetic material within the plant cell. The dynamics of stromule formation and extension are influenced by various factors, including developmental stage, environmental stimuli, and the overall metabolic state of the cell.

While stromules are most frequently observed extending from chloroplasts, they can also originate from other types of plastids, such as leucoplasts and amyloplasts. Their formation involves the coordinated remodeling of the plastid membrane and the cytoskeleton, with actin filaments and microtubules playing a key role in their elongation and stabilization. Research into stromule dynamics and function is ongoing, with current studies focused on elucidating the precise mechanisms underlying their formation, the nature of the molecules they transport, and their overall contribution to plant cell biology.