Diethyl aminoethyl hexanoate (DA-6), an artificial tertiary amine, is a plant growth regulator that has been applied to many plant species, such as maize, cotton, soybean, peanut, and tomato. Extensive studies have demonstrated that DA-6 has many beneficial effects on agricultural production, including increasing the photosynthetic rate and yields, promoting biomass accumulation, and improving germination and seedling establishment of naturally and artificially aged soybean seeds. Moreover, DA-6 can accelerate microalgal growth and enhance the quantity and quality of lipids for biodiesel production. Combining DA-6 and high light can promote astaxanthin accumulation in green microalgae. DA-6 also plays important roles in improving the defence response of plants under diverse environmental stresses, such as salinity stress, chilling stress and heavy metal stress. DA-6 can be used to alleviate salinity stress by inducing the advantageous effects of salinity tolerance and decreasing oxidative damage]. Foliar sprays of DA-6 can increase cadmium extraction efficiency and can alleviate metal toxicity. DA-6 can also be used in combination with other plant growth regulators and/or phytohormones. Numerous studies have shown the physiological effects of DA-6, but the molecular mechanism remains unknown.

DA-6 has been applied at many stages, including germination, seedling growth, and flowering. The dissipation half-lives of DA-6 are 1.1–2.2 days, 5.4–8.2 days and 1.5–1.9 days in pakchoi, in cotton, and in the soil, respectively. Rapid degradation of DA-6 would be beneficial for the safe use of DA-6. Spraying DA-6 at the seedling stage can promote plant growth by enhancing photosynthesis and regulating hormone balance in maize and soybean. However, the molecular mechanism by which spraying DA-6 after anthesis influences wheat is still unknown.

Grain weight is a crucial component of grain yield and is significantly influenced by DA-6 levels. Some genes and signalling pathways that determine seed size (grain weight) have been identified, such as the ubiquitin–proteasome pathway, the mitogen-activated protein kinase signalling pathway, genes involved in G-protein signalling and phytohormones and genes that encode transcriptional regulatory factors. DA-6 can increase protein contents in plants. Moreover, genes, environmental conditions, and cultivation patterns also affect seed protein content, which is related to both wheat end use and seed vigour. However, the effects of spraying DA-6 after anthesis on wheat grain weight and seed protein content remain unknown.

In this study, the results showed that spraying DA-6 after anthesis increased wheat grain weight and seed protein content. Transcriptome analysis subsequently showed that DA-6 affected plant hormone signal transduction and sucrose synthesis in the flag leaves, protein processing in endoplasmic reticulum (ER) in the stems, and starch synthesis and protein processing in ER in the seeds. Upregulated genes involved in sucrose synthesis in the flag leaves and starch synthesis in the seeds might be associated with increased 1000-grain weight and genes involved in protein processing in ER in both the stems and seeds might contribute to enhanced seed protein content.