Plastid-nuclear complexes: permanent structures in photosynthesizing tissues of vascular plants

Communication between the cytosol and organelles has been much studied in plant cells, while the nature of direct interaction of nuclei and chloroplasts, and the interaction of tubular and saccular networks derived by them, are still a challenge to research. Here we show by the use of several microscopy methods and techniques that different compact plastid-nuclear complexes (PNCs) are permanent structures of cells in gymnosperms and angiosperms like juniper (Juniperus communis), tobacco (Nicotiana tabaccum), garden onion (Allium cepa) and other plants. PNC acts in a continuous interrelated three-level movement: (i) by slowly tumbling the whole PNC in a fixed locality of a cell; (ii) by rocking of some chloroplasts near the nucleus; (iii) by rushing of many nuclear derivatives (endoplasmic reticulum, dictyosomes) at relatively high speed among the PNCs and other cell structures. It can be suggested that PNCs provide beneficial exchange of substances between the chloroplasts and nucleus, thus inhibiting formation of gerontoplasts during the senescence of cells.