Fig. 6: A schematic model delineating a signaling pathway that integrates Fe and P availability cues to regulate chlorophyll accumulation and photosynthesis genes.
From: Interdependent iron and phosphorus availability controls photosynthesis through retrograde signaling
Fe deficiency (−Fe+P) causes a decrease in the expression of bZIP58 that is central to controlling the transcription of nuclear-encoded photosynthetic genes. P limitation under Fe deficiency (−Fe−P) prevents this downregulation of bZIP58 and induces VTC4. The induction of VTC4 expression requires bZIP58, whose effect could be direct or indirect, represented here by “X”. We propose that induction of VTC4 increases ascorbic acid in the chloroplast mediated by PHT4;4. We hypothesize that the increase of ascorbic acid level prevents ROS accumulation, thus maintaining the expression of bZIP58 and its downstream photosynthesis genes and leading to the “stay-green” phenotype. The figure was created with BioRender.com.
