Plant growth stimulation by high CO2 depends on phosphorus homeostasis in chloroplasts.

Elevated atmospheric CO2 enhances photosynthetic rate,1 thereby increasing biomass production in plants. Nevertheless, high CO2 reduces the accumulation of essential nutrients2 such as phosphorus (P),3 which are required for photosynthetic processes and plant growth. How plants ensure enhanced growth despite meager P status remains enigmatic. In this study, we utilize genome-wide association analysis in Arabidopsis thaliana to identify a P transporter, PHT4;3, which mediates the reduction of P in chloroplasts at high CO2. Decreasing chloroplastic P fine-tunes the accumulation of a sugar-P metabolite, phytic acid, to support plant growth. Furthermore, we demonstrate that this adaptive mechanism is conserved in rice. Our results establish a mechanistic framework for sustainable food production against the backdrop of soaring CO2 levels across the world.

Interdependent iron and phosphorus availability controls photosynthesis through retrograde signaling.

Iron deficiency hampers photosynthesis and is associated with chlorosis. We recently showed that iron deficiency-induced chlorosis depends on phosphorus availability. How plants integrate these cues to control chlorophyll accumulation is unknown. Here, we show that iron limitation downregulates photosynthesis genes in a phosphorus-dependent manner. Using transcriptomics and genome-wide association analysis, we identify two genes, PHT4;4 encoding a chloroplastic ascorbate transporter and bZIP58, encoding a nuclear transcription factor, which prevent the downregulation of photosynthesis genes leading to the stay-green phenotype under iron-phosphorus deficiency. Joint limitation of these nutrients induces ascorbate accumulation by activating expression of an ascorbate biosynthesis gene, VTC4, which requires bZIP58. Furthermore, we demonstrate that chloroplastic ascorbate transport prevents the downregulation of photosynthesis genes under iron-phosphorus combined deficiency through modulation of ROS homeostasis. Our study uncovers a ROS-mediated chloroplastic retrograde signaling pathway to adapt photosynthesis to nutrient availability.

Plant resilience to phosphate limitation: current knowledge and future challenges.

Phosphorus (P) is an essential macronutrient for all living organisms. Importantly, plants require a large amount of P to grow, and P deficiency causes huge losses in plant production. Although this issue can be mitigated by the appropriate use of phosphate (Pi) rock-derived P fertilizers, phosphate rock is a finite natural resource. Moreover, the increased demand for food as a result of our growing global population is another factor contributing to a prospective P crisis. While creating crops that are resilient to Pi deficiency presents great scientific challenge, the current progress in our understanding of how plants regulate Pi homeostasis offers some opportunities for further study. In this review, we present the published research supporting these opportunities, which are based on the molecular mechanisms that plants have evolved to respond to P deficiency. First, we focus on recent advances in P sensing and signaling pathways in the regulation of root system architecture. Next, we describe the mechanisms that regulate Pi transport and accumulation, in a Pi- (or other nutrient) dependent manner. Integrating these data will help to design an innovative strategy for improving Pi nutrition in plants. In addition, this will help with Pi scarcity, one of the challenges facing agriculture in the twenty first century.