PI3K is involved in nucleolar structure and function on root-tip meristematic cells of Triticum aestivum L.

In this study, wheat (Triticum aestivum L.) seeds were used to detect the effect of wortmannin, a specific inhibitor of PI3K, on the nucleolar structure and function. When the germinated seeds were treated with wortmannin, it was shown that the root growth was suppressed and the mitotic index was decreased. The inhibition effects were positively correlated with the concentrations of the drug. The observations of light and transmission electron microscopy revealed that the nucleolar morphology became irregular and their fine structure disappeared. Some granules with a size range of 0.05–0.30 μm diffused from the nucleoli and gradually moved to the nucleoplasm between or around the chromatin. Indirect immunofluorescence staining indicated that B23 shuttled from the nucleoli to the nucleoplasm, or even, to the cytoplasm. RT-PCR technique demonstrated that the expression of C23 was severely down-regulated. Our results suggest, for the first time, that wortmannin treatment can not only damage nucleolar structure, but also inhibit its function, implying that PI3K is involved in nucleolar structure and function.