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 Metabolic Network 15: A resource of genome-wide metabolism databases for 126 plants and algae.

To understand and engineer plant metabolism, we need a comprehensive and accurate annotation of all metabolic information across plant species. As a step towards this goal, we generated genome-scale metabolic pathway databases of 126 algal and plant genomes, ranging from model organisms to crops to medicinal plants (https://plantcyc.org). Of these, 104 have not been reported before. We systematically evaluated the quality of the databases, which revealed that our semi-automated validation pipeline dramatically improves the quality. We then compared the metabolic content across the 126 organisms using multiple correspondence analysis and found that Brassicaceae, Poaceae, and Chlorophyta appeared as metabolically distinct groups. To demonstrate the utility of this resource, we used recently published sorghum transcriptomics data to discover previously unreported trends of metabolism underlying drought tolerance. We also used single-cell transcriptomics data from the Arabidopsis root to infer cell type-specific metabolic pathways. This work shows the quality and quantity of our resource and demonstrates its wide-ranging utility in integrating metabolism with other areas of plant biology.

Genome-enabled discovery of anthraquinone biosynthesis in Senna tora.

Senna tora is a widely used medicinal plant. Its health benefits have been attributed to the large quantity of anthraquinones, but how they are made in plants remains a mystery. To identify the genes responsible for plant anthraquinone biosynthesis, we reveal the genome sequence of S. tora at the chromosome level with 526 Mb (96%) assembled into 13 chromosomes. Comparison among related plant species shows that a chalcone synthase-like (CHS-L) gene family has lineage-specifically and rapidly expanded in S. tora. Combining genomics, transcriptomics, metabolomics, and biochemistry, we identify a CHS-L gene contributing to the biosynthesis of anthraquinones. The S. tora reference genome will accelerate the discovery of biologically active anthraquinone biosynthesis pathways in medicinal plants.

[Effects of enflurane on myocardial reperfusion injury during cardiac surgery with cardiopulmonary bypass].

OBJECTIVE: To study the effects of inhalation enflurane (Enf) before aortic clamping on myocardial reperfusion injury in cardiac surgery with cardiopulmonary bypass (CPB). METHODS: hirty patents undergoing selective cardiac valve replacement were randomly allocated to three groups. Group I and group II inhaled 1.0 MAC and 0.5 MAC Enf before clamping aorta, respectively. Group III was the control group interval administration with Fentanyl. RESULTS: Immediately upon aortic clamp release (T2), the value of CK-MB, MDA and SOD of all the groups was significantly increased, however,their concentration did not peak significantly until T3 and T4(10 and 30 min after clamp aorta release). The levels at 60 min (T5) and 24 hours (T6) aorta were lower than T4 but still higher than T(0). At T3 and T4, CK-MB levels in group I were significantly higher than those in II and III groups (P=0.0220, 0.0108 and 0.0202, 0.0295). At T6, the CK-MB level of group II was significantly higher than that of group III (P<0.0001). At T4 and T5, the MDA value of group I was higher than that of group II (P=0.0060 and 0.0364). Meanwhile, the SOD level in group I was also higher than that of group II and group III at the T4 point (P<0.0001 and 0.0084). There was a correlation between the CK-MB value and the aorta clamping time,correlation coefficient range being 0.55 - 0.81,(P<0.05). However, there was no correlation between the CK-MB and MDA, SOD. CONCLUSION: There is ischemia reperfusion injury during cardiac surgery CPB with the increase of OFR production and elevation of the antioxidant reserve. Inhalation of large dose of enflurane may result in increased myocardial ischemia reperfusion injury manifested by elevated levels of myocardial enzymes and OFR production.