Figure 3.

Mispositioning of the SPK in a kipA mutant. (A) Correlation between SPK position and growth direction. Top, noncentral SPK (arrow) in a hypha of ΔkipA mutant strain SSK13. Bottom, 5 min later, growth has occurred in the direction of the noncentral SPK. (B) Determination of SPK position in wild-type (top, RMS011) and ΔkipA mutant (bottom, SSK44) hyphae. The center of the tip and central axis of the hypha were defined as indicated by the lines, and SPK position was determined by measuring the distance from the center of the SPK to the central axis and expressing the value as a percentage of the radius of the hypha (i.e., the distance from the central axis to the outer edge of the hypha at the position indicated by the line perpendicular to the central axis). (C, left) Examples of tracks of SPKs in wild-type (RMS011) and ΔkipA (SSK44) strains. The shaded box represents (top to bottom) half the diameter of the hypha in each case; the straight line represents its central axis and a time period of 10 min over which measurements were made. (C, right) Summary of data for 129 measurements (17 germlings) on strain RMS011 and 121 measurements (28 germlings) on strain SSK44. The average (shaded box) and maximum (white box) distances of the SPK from the central axis are indicated. Note that, in some cases, the SPKs moved considerably further from the central axis than seen in the typical tracks shown on the left.