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. 2010 Jan 1;21(1):18–28. doi: 10.1091/mbc.E09-01-0063

Figure 2.

Figure 2.

Oscillation, rotation and bypassing of nuclei in an A. gossypii hypha. Hyphae expressing AgH4-GFP to mark nuclei (green) and AgTub4-RedStar2 to mark SPBs (red) were pregrown and mounted for fluorescence videomicroscopy at room temperature as described in Materials and Methods. GFP and red fluorescent protein (RFP) fluorescence was imaged for 500 ms each in five Z-planes, 0.75 μm apart at 1-min intervals and processed (Supplemental Movie S1). (A) Maximal projections at 11 time points showing frequent changes in the position and SPB orientation of the 11 nuclei monitored in Supplemental Movie S1. During the 110 analyzed 1-min time intervals, nuclei moved forward 34 times and backward 30 times, all of which were led by the SPB. During the remaining 46 intervals, nuclei moved only marginally. Nonmoving as well as moving nuclei rotated during 53 intervals by up to 180° as seen by changes of the SPB positions. The relative position of SPBs in all fast-moving nuclei was “head-first” (at the leading edge of nuclear movement), and inversions in the direction of nuclear movement were preceded by inversion of the SPB position. Bar, 5 μm. (B). Diagram of the position of nuclei (circles) and orientation of SPBs (red dots) at 0 and 10 min. Identical nuclei are connected by dotted lines highlighting the four bypassing events. The arrow marks the 1.5-μm elongation of the hypha during 10 min, which was measured using the overilluminated montage of A to visualize the background staining of the hyphal cytoplasm. (C). Detailed diagrammatic presentation of backward and forward as well as rotational movements of two nuclei (6, white asterisk and 7, yellow asterisk) within 10 min (movie frames 3–13 of Supplemental Movie S1). Nucleus 6 bypasses nucleus 7 by migrating 5 μm backward, inverts the position of the SPB by rotation at 4 and 5 min, and migrates 3 μm forward. Nucleus 7 represents a typical tumbling nucleus showing minor movements and small angle rotations until 8 min, at which time it undergoes a rotation and then a forward movement of 2 μm. Fast-moving nuclei in A and C seem to be stretched and sometimes display two SPBs. This does not reflect the real shape of fast nuclei or duplicated SPBs however; rather, it is due to the high migration speed and the fact that these images show projections of five focal planes taken within 6 s.