Figure 2.

H₂O₂-mediated retrograde signaling. Chloroplasts, mitochondria, and peroxisomes are linked together to facilitate the shuttling of intermediate metabolites between them. When plants are subjected to environmental stresses, a large amount of H₂O₂ is produced in these three organelles. H₂O₂ can be used as a signal molecule to regulate the expression of nuclear response genes through the MAPK cascade or potentially through other unknown pathways. H₂O₂ in chloroplasts also promotes the dissociation of the transcription factor PTM from the chloroplast membrane to regulate nuclear gene expression. M, mitochondria; C, chloroplast; P, peroxisome; N, nucleus.