Investigating the Role of MicroRNA396 (miR396) Gene in Regulating Wheat Yield and Grain Nitrogen Concentration

Nitrogen (N) is essential for crop growth, yet excessive fertilization causes environmental issues, highlighting the need to sustain yield and grain N concentration under reduced N input. miR396s are known to regulate plant development and stress responses. Here, we examined whether and how miR396 affects wheat yield and N status under high and low N conditions. TaMIM396 (transforming with the target mimicry construct of miR396) overexpression significantly increased plant height, spike length, grain yield, and grain N concentration under both N treatments. Physiological data showed TaMIM396 enhanced dry matter (DM) and N accumulation at anthesis and maturity, as well as improved post-anthesis remobilization of DM and N to grains. RNA-seq analysis revealed that, under low N, TaMIM396 specifically upregulated key photosynthetic antenna genes, including Lhca3 and Lhcb1/2/3/5, which are critical for light harvesting, suggesting improved photosynthetic efficiency that promotes DM accumulation under N limitation. Collectively, our results demonstrate that TaMIM396 acts as a broad-spectrum N-efficiency gene, coordinating carbon and N remobilization while boosting photosynthetic capacity, thereby supporting stable yield and grain N concentration across N supply levels. Therefore, TaMIM396 is a promising candidate for breeding N-efficient wheat cultivars compatible with sustainable high-yield agriculture.