Retrograde signaling establishes a feedback loop where signals travel backward from the chloroplasts to the nucleus, eliciting responses. This intricate regulatory network comprises specific sensor molecules that move from the chloroplast to the nucleus via the cytosol, managing the essential expression of nuclear genes and conveying information about these energy-transducing organelles’ functional and physiological states. In plants, plastid-mediated retrograde signaling operates through two pathways: the biogenic signaling pathway, which activates during early development, and the operational signaling pathway, which modulates the functional status of chloroplasts amid environmental stress. Many researchers believe that GUN1 (GENOMES UNCOUPLED), a chloroplast-localized protein, plays a crucial role in biogenic retrograde communication. However, relatively little is known about the signaling components and activities involved in the operational pathways. This review focuses on the involvement of signaling components, sensor molecules, and processes in intracellular signaling pathways that coordinate gene expression between the chloroplast and nucleus during various environmental stressors.