A cross-scale analysis to understand and quantify the effects of photosynthetic enhancement on crop growth and yield across environments

Photosynthetic manipulation provides new opportunities for enhancing crop yield. However, understanding and quantifying the importance of individual and multiple manipulations on the seasonal biomass growth and yield performance of target crops across variable production environments is limited. Using a state-of-the-art cross-scale model in the APSIM platform we predicted the impact of altering photosynthesis on the enzyme-limited (A_c) and electron transport-limited (A_j) rates, seasonal dynamics in canopy photosynthesis, biomass growth, and yield formation via large multiyear-by-location crop growth simulations. A broad list of promising strategies to improve photosynthesis for C₃ wheat and C₄ sorghum were simulated. In the top decile of seasonal outcomes, yield gains were predicted to be modest, ranging between 0% and 8%, depending on the manipulation and crop type. We report how photosynthetic enhancement can affect the timing and severity of water and nitrogen stress on the growing crop, resulting in nonintuitive seasonal crop dynamics and yield outcomes. We predicted that strategies enhancing A_c alone generate more consistent but smaller yield gains across all water and nitrogen environments, A_j enhancement alone generates larger gains but is undesirable in more marginal environments. Large increases in both A_c and A_j generate the highest gains across all environments. Yield outcomes of the tested manipulation strategies were predicted and compared for realistic Australian wheat and sorghum production. This study uniquely unpacks complex cross-scale interactions between photosynthesis and seasonal crop dynamics and improves understanding and quantification of the potential impact of photosynthesis traits (or lack of it) for crop improvement research.     

The recycling itinerary of the 46 kDa mannose 6-phosphate receptor--Golgi to late endosomes--coincides with that of the 215 kDa M6PR

The intracellular distribution and trafficking of the 46 kDa mannose 6-phosphate (M6PR) receptor has been investigated in rat Clone 9 hepatocytes and NRK cells and compared to that of the 215 kDa M6PR. Antibodies were generated to a synthetic peptide corresponding to the last 15 amino acids of the C-terminal cytoplasmic domain of the 46 kDa M6PR and used to localize it by immunofluorescence and immunoperoxidase labeling. At steady state the 46 kDa M6PR was concentrated at its presumptive sorting site in the Golgi complex, mainly in middle and trans cisternae. In cells treated with chloroquine or NH4Cl, the receptor was found in swollen multivesicular endosomes as well as in Golgi cisternae. When chloroquine-treated cells were double labeled with antibodies to both the 215 and 46 kDa M6PR, all of the endosomes which contained detectable 46 kDa also contained 215 kDa receptor. Thus, after weak base treatment, the 46 kDa receptor is located in a compartment which corresponds to the delivery site of the 215 kDa receptor, previously identified as a late endosome (Woods, J. W., J. Goodhouse, M. G. Farquhar, Eur. J. Cell Biol. 50, 132-143 (1989]. We conclude that the intracellular itinerary of the 46 kDa M6PR is similar to that of the 215 kDa M6PR in that both receptors cycle between the Golgi complex and the same population of late endosomes (prelysosomes). However, the distribution of the two receptors along the recycling route varies under identical conditions in these two cell types.(ABSTRACT TRUNCATED AT 250 WORDS)     

Critical review: incorporating the arrangement of mitochondria and chloroplasts into models of photosynthesis and carbon isotope discrimination

Photosynthesis Research - The arrangement of mitochondria and chloroplasts, together with the relative resistances of cell wall and chloroplast, determine the path of diffusion out of the leaf for...