Spatial Distribution Characterization of Hormonal Metabolites in Morphologically Diverse Jujube Fruits via MALDI-MS Imaging

Ziziphus jujuba Mill. is an important economic tree species in China with nutritional, ecological and ornamental values, and its fruits show abundant variations in size and shape. Phytohormones regulate fruit morphogenesis, yet the spatial distribution characteristics of endogenous phytohormones in jujube fruits with different shapes remain unclear. In this study, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was applied to explore the spatial distribution patterns of phytohormones in round, constricted and long jujube fruits. The results indicated that phytohormones were uniformly distributed in the flesh and pericarp of round and constricted fruits. Certain auxins and gibberellins were undetectable in the outer pericarp of long fruits, while one cytokinin was predominantly accumulated at the fruit base. The differential distribution of phytohormones is likely a potential factor triggering jujube fruit morphological differentiation. This study clarifies the spatial variation in endogenous phytohormones, helping elucidate the regulatory mechanism of jujube fruit shape.