Profiling of phytohormones in rice under elevated cadmium concentration levels by magnetic solid-phase extraction coupled with liquid chromatography tandem mass spectrometry.

Phytohormones, a collection of signal small molecules with various structures, regulate a series of physiological processes of plants. For instance, they regulate the growth and development, response to biotic and abiotic stresses. Quantification of trace endogenous phytohormones is essential to elucidate their molecular mechanisms in response to stresses. However, the structural and chemical diversity of phytohormones make it difficult to purify and enrich multiple phytohormones in one-step. In the current study, a method was developed to comprehensively profile phytohormones, including 8 cytokinins (CKs), indole-3-acetic acid (IAA), abscisic acid (ABA), jasmonic acid (JA) and 10 gibberellins (GAs) by Fe3O4@TiO2-based magnetic solid-phase extraction coupled with ultra-performance liquid chromatography-electrospray tandem mass spectrometry (Fe3O4@TiO2-based MSPE-UPLC-MS/MS). In the proposed method, the phytohormones in the acetonitrile extract of plant tissues were captured and purified by one-step MSPE using Fe3O4@TiO2 as a sorbent prior to UPLC-MS/MS analysis. The sensitivity, accuracy and reproducibility of the proposed analytical method were demonstrated to satisfy the profiling of multiple phytohormones in plant tissue. We then further used the Fe3O4@TiO2-based MSPE-UPLC-MS/MS method to explore the change of phytohormones in rice under Cd stress. The results showed that CKs, IAA, ABA, JA and biological active GAs all increased under Cd stress, suggesting that these phytohormones may take part in response to Cd stress. The study may promote the further understanding of the physiological functions of phytohormones in response to Cd stress.