Microtubule organization during the development of the mitotic apparatus in cultured mesophyll protoplasts of higher plants – an immunofluorescence microscopic study

Abstract

Microtubule organization in the course of the interphase‐mitosis transition, karyokinesis and cytokinesis in cultured mesophyll protoplasts of Medicago sativa L. cv. Regen S and Nicotiana tabacum L. cv. Wisconsin 38 was investigated during the early culture stages. A prominent circular band of microtubules, the prophase band of microtubules (PB) was seen in the cell cortex during prophase in most cells. The band appeared during very early prophase and disappeared during late prophase. Other prophase microtubule arrays were nuclear‐envelope associated microtubule fluorescence (perinuclear fluorescence, PNF) and groups of microtubules radiating from the nuclear envelope into the cytoplasm. These radiating microtubutes (perinuclear radiating microtubules, PNR) were particularly long and prominent in the PB plane appearing to link the PNF with the PB network. The possible functions of the PNR are discussed. The role of the PB is discussed in the light of the unorganized nature of these cells.