By 2021, nearly 9% of the global population was still suffering from hunger. It has estimated that the world population will reach 9.7 billion in 2050 (United Nations, 2019; Tian et al., 2021), which requires a 2.4% increase per year for the yields of major crops. However, current growth rates are only half of this, imposing serious challenges in increasing grain yield by crop breeding. Plant growth and development mainly require energy and nutrients, and thus it is generally considered that the crop yield could be increased by elevating photosynthetic efficiency and higher nitrogen-use efficiency. Moreover, the uptake and transport of nitrogen must be coordinated with carbon fixation and production of carbohydrates by photosynthesis. However, effective strategies for optimizing the carbon/nitrogen status in crops are still relatively limited and therefore require new promising targets.