Source-sink dynamics in field-grown durum wheat under contrasting nitrogen supplies: key role of non-foliar organs during grain filling

20 páginas, 9 figurasThe integration of high-throughput phenotyping and metabolic approaches is a suitable strategy to study the genotype-by-environment interaction and identify novel traits for crop improvement from canopy to an organ level. Our aims were to study the phenotypic and metabolic traits that are related to grain yield and quality at canopy and organ levels, with a special focus on source-sink coordination under contrasting N supplies. Four modern durum wheat varieties with contrasting grain yield were grown in field conditions under two N fertilization levels in north-eastern Spain. We evaluated canopy vegetation indices taken throughout the growing season, physiological and metabolic traits in different photosynthetic organs (flag leaf blade, sheath, peduncle, awn, glume, and lemma) at anthesis and mid-grain filling stages, and agronomic and grain quality traits at harvest. Low N supply triggered an imbalance of C and N coordination at the whole plant level, leading to a reduction of grain yield and nutrient composition. The activities of key enzymes in C and N metabolism as well as the levels of photoassimilates showed that each organ plays an important role during grain filling, some with a higher photosynthetic capacity, others for nutrient storage for later stages of grain filling, or N assimilation and recycling. Interestingly, the enzyme activities and sucrose content of the ear organs were positively associated with grain yield and quality, suggesting, together with the regression models using isotope signatures, the potential contribution of these organs during grain filling. This study highlights the use of holistic approaches to the identification of novel targets to improve grain yield and quality in C3 cereals and the key role of non-foliar organs at late-growth stages.This study was supported by the projects AGL2016-76527-R and PID2019-106650RB-C22, funded by the Spanish Ministry of Science and Innovation, and the projects CSI260P20 and CLU-2019-05-IRNASA/CSIC Unit of Excellence funded by the Junta de Castilla y León and co-financed by the European Union (ERDF). We also acknowledge the support of FCT—Fundaçãopara a Ciência e a Tecnologia, I.P., through the R&D Unit GREEN-IT -Bioresources for Sustainability (UIDB/04551/2020 and UIDP/04551/2020). RMP was the recipient of an FPI-INIA fellowship from the Spanish Ministry of Science and Innovation (CPD2016-0107)Peer reviewe

Dissecting the subcellular compartmentation of proteins and metabolites in arabidopsis leaves using non-aqueous fractionation

Non-aqueous fractionation is a technique for the enrichment of different subcellular compartments derived from lyophilized material. It was developed to study the subcellular distribution of metabolites. Here we analyzed the distribution of about 1,000 proteins and 70 metabolites, including 22 phosphorylated intermediates in wild-type Arabidopsis rosette leaves, using non-aqueous gradients divided into 12 fractions. Good separation of plastidial, cytosolic, and vacuolar metabolites and proteins was achieved, but cytosolic, mitochondrial, and peroxisomal proteins clustered together. There was considerable heterogeneity in the fractional distribution of transcription factors, ribosomal proteins, and subunits of the vacuolar-ATPase, indicating diverse compartmental location. Within the plastid, sub-organellar separation of thylakoids and stromal proteins was observed. Metabolites from the Calvin-Benson cycle, photorespiration, starch and sucrose synthesis, glycolysis, and the tricarboxylic acid cycle grouped with their associated proteins of the respective compartment. Nonaqueous fractionation thus proved to be a powerful method for the study of the organellar, and in some cases sub-organellar, distribution of proteins and their association with metabolites. It remains the technique of choice for the assignment of subcellular location to metabolites in intact plant tissues, and thus the technique of choice for doing combined metabolite-protein analysis on a single tissue sample

The interplay between carbon availability and growth in different zones of the growing maize leaf

Plants assimilate carbon in their photosynthetic tissues in the light. However, carbon is required during the night and in nonphotosynthetic organs. It is therefore essential that plants manage their carbon resources spatially and temporally and coordinate growth with carbon availability. In growing maize (Zea mays) leaf blades, a defined developmental gradient facilitates analyses in the cell division, elongation, and mature zones. We investigated the responses of the metabolome and transcriptome and polysome loading, as a qualitative proxy for protein synthesis, at dusk, dawn, and 6, 14, and 24 h into an extended night, and tracked whole-leaf elongation over this time course. Starch and sugars are depleted by dawn in the mature zone, but only after an extension of the night in the elongation and division zones. Sucrose (Suc) recovers partially between 14 and 24 h into the extended night in the growth zones, but not the mature zone. The global metabolome and transcriptome track these zone-specific changes in Suc. Leaf elongation and polysome loading in the growth zones also remain high at dawn, decrease between 6 and 14 h into the extended night, and then partially recover, indicating that growth processes are determined by local carbon status. The level of Suc-signaling metabolite trehalose-6-phosphate, and the trehalose-6-phosphate: Suc ratio are much higher in growth than mature zones at dusk and dawn but fall in the extended night. Candidate genes were identified by searching for transcripts that show characteristic temporal response patterns or contrasting responses to carbon starvation in growth and mature zones

The interplay between carbon availability and growth in different zones of the growing maize leaf

Plants assimilate carbon in their photosynthetic tissues in the light. However, carbon is required during the night and in nonphotosynthetic organs. It is therefore essential that plants manage their carbon resources spatially and temporally and coordinate growth with carbon availability. In growing maize (Zea mays) leaf blades, a defined developmental gradient facilitates analyses in the cell division, elongation, and mature zones. We investigated the responses of the metabolome and transcriptome and polysome loading, as a qualitative proxy for protein synthesis, at dusk, dawn, and 6, 14, and 24 h into an extended night, and tracked whole-leaf elongation over this time course. Starch and sugars are depleted by dawn in the mature zone, but only after an extension of the night in the elongation and division zones. Sucrose (Suc) recovers partially between 14 and 24 h into the extended night in the growth zones, but not the mature zone. The global metabolome and transcriptome track these zone-specific changes in Suc. Leaf elongation and polysome loading in the growth zones also remain high at dawn, decrease between 6 and 14 h into the extended night, and then partially recover, indicating that growth processes are determined by local carbon status. The level of Suc-signaling metabolite trehalose-6-phosphate, and the trehalose-6-phosphate:Suc ratio are much higher in growth than mature zones at dusk and dawn but fall in the extended night. Candidate genes were identified by searching for transcripts that show characteristic temporal response patterns or contrasting responses to carbon starvation in growth and mature zones

Trehalose 6-phosphate coordinates organic and amino acid metabolism with carbon availability

Trehalose 6-phosphate (Tre6P) is an essential signal metabolite in plants, linking growth and development to carbon metabolism. The sucrose-Tre6P nexus model postulates that Tre6P acts as both a signal and negative feedback regulator of sucrose levels. To test this model, short-term metabolic responses to induced increases in Tre6P levels were investigated in Arabidopsis thaliana plants expressing the Escherichia coli Tre6P synthase (otsA) under the control of an ethanol-inducible promoter. Increased Tre6P led to a transient drop in sucrose content, post-translational activation of nitrate reductase and phosphoenolpyruvate carboxylase, and increased levels of organic and amino acids. Radio- (14CO2) and stable-isotope (13CO2) labelling experiments showed no change in the rates of photoassimilate export in plants with elevated Tre6P, but increased flux of carbon into organic acids. It is concluded that high Tre6P lowers sucrose levels by stimulating nitrate assimilation and anaplerotic synthesis of organic acids, thereby diverting photoassimilates away from sucrose to generate carbon skeletons and fixed nitrogen for amino acid synthesis. These results are consistent with the sucrose-Tre6P nexus model and implicate Tre6P in coordinating carbon and nitrogen metabolism in plants.Fil: Figueroa, Carlos Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Feil, Regina. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Ishihara, Hirofumi. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Watanabe, Mutsumi. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Kölling, Katharina. Institute of Agricultural Sciences; SuizaFil: Krause, Ursula. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Höhne, Melanie. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Encke, Beatrice. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Plaxton, William C.. Queens University; CanadáFil: Zeeman, Samuel C.. Institute of Agricultural Sciences; SuizaFil: Li, Zhi. Universidad de Hohenheim; AlemaniaFil: Schulze, Waltraud X.. Universidad de Hohenheim; AlemaniaFil: Hoefgen, Rainer. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Stitt, Mark. Max Planck Institute of Molecular Plant Physiology; AlemaniaFil: Lunn, John E.. Max Planck Institute of Molecular Plant Physiology; Alemani