Plausible Photosynthetic Parameters that Contribute to Differences in Grain Protein Content among Rice Genotypes

Abstract

Abstract Aim Attempts to increase grain protein content (GPC) most often resulted in a reduction of yield in cereals. This trade-off between GPC and yield rises mainly because of shared source of reductants for carbon and nitrogen assimilation. The major intent of this study was to understand this trade-off between GPC and grain yield in rice. Methods Based on a previous study, we identified two genotypes contrasting GPC with comparable yield and photosynthesis. We articulated the interrelation between carbon and nitrogen assimilation to understand the phenomenon that led to higher GPC without compromising its yield among the contrasts. We also looked at how these genotypes behaved to ambient and low light intensities in terms of photosynthesis and protein synthesis under limiting electron source. Results Our findings suggested that under ambient light, the high GPC genotype has adopted the triose phosphate utilization limitation as a traffic switch to limit the flow of electrons to carbon assimilation and divert the excess electrons to other sinks. The diversion of extra electrons particularly to nitrite reduction is boosted by increased substrates from higher uptake, transport and metabolism of nitrogen in leaf. In low GPC genotype under ambient light intensity excess electrons were quenched in the form of heat. Conclusions These findings suggest that efficiency in utilization of electrons by adopting a switch called TPU limitation coupled with better remobilization efficiency can be a promising genotype for breeders to develop a high yielding variety complemented with high GPC.