Chloroplasts and Plant Sustainability: Key Roles and Emerging Insights.

Chloroplasts are the primary sites of photosynthesis, but growing evidence highlights their broader role as central hubs that coordinate plant responses to environmental challenges. They retain a semi-autonomous genetic system and communicate extensively with the nucleus through anterograde and retrograde signalling pathways, enabling coordinated cellular regulation. Beyond energy conversion, chloroplasts host key biosynthetic pathways and dynamically adjust their metabolic and redox states in response to developmental and environmental cues. This review summarizes the current knowledge of chloroplast functions in response to abiotic and biotic stresses, emphasizing their contribution to plant resilience, productivity and sustainability. Under abiotic stress, chloroplasts undergo structural, metabolic and redox reprogramming to maintain photosynthetic efficiency and metabolic homeostasis. During biotic stress, they act as a powerful signalling platform that integrates immune responses with metabolic and redox regulation. These functions rely on overlapping signalling pathways that are differentially tuned to support acclimation or defence. By coordinating stress responses with photosynthetic activity and metabolic efficiency, chloroplasts play a central role in sustaining plant productivity and represent promising targets for enhancing crop resilience and agricultural sustainability under climate change and increasing pathogen pressure.