iTRAQ proteome analysis reveals the underling mechanisms of foliage zinc-spraying to improve photosynthetic capacity and seed yields of Peaonia ostii ‘Fengdan’

Zinc (Zn) deficiency is a significant nutritional limitation to crop yield globally, particularly in calcareous soil environments. Tree peony of Peaonia ostii 'Fengdan' is regarded as an oil crop due to its seeds rich in alpha-linolenic acid, a beneficial compound for health promotion. However, low seed yield remains a primary challenge in attaining sufficient seed oil from tree peony. In this study, Zn fertilization was applied to soil or foliage of P. ostii 'Fengdan' in the growth period before fruit development. Our findings reveal that foliar Zn-spraying, as opposed to soil application, proves to be a more effective method for augmenting seed yield, Zn accumulation and photosynthetic capacity in 'Fengdan'. Comparative analyses of the leaf proteome of 'Fengdan' using iTRAQ profiling under foliar Zn-spraying identified 115 differentially expressed proteins (DEPs), including 36 upregulated proteins, which likely contribute to the observed increase in seed yields of 'Fengdan' caused by foliage Zn-spraying. Specifically, Zn