Figure 2.
Figure 2. F-actin is essential for the ingression of incipient septum rudiments. (A) Septation in cells treated with LatA. All the open septa (open arrowheads) except septum rudiments (arrows) progress to completion (closed arrowheads) in cells grown in the presence of LatA. Cells grown as in Fig. 1 D were shifted to YES containing LatA (100 µM; time 0) and analyzed by CW fluorescence microscopy. Scale bar = 5 μm. (B) The percentage of cells with septa divided into different length intervals as indicated was quantified in CW-stained cells as in A. After a long LatA treatment (1 h), most cells displayed either septum rudiments or complete septa (n = 1,077 septa). (C) LatA treatment in cells with septum rudiments causes Bgs1, Bgs4, and Ags1 glucan synthase spreading, forming large lateral bands (arrows). Cells were grown as in A and simultaneously analyzed by RFP, GFP, and CW fluorescence microscopy after 15 min with LatA. Scale bar = 2 μm. (D) Time-lapse sequences from incipient septation to completion in the absence of LatA (top panel) or from incipient septation to ingression arrest and spreading of Bgs1 in the presence of LatA (middle and bottom panels). Cells grown as in Fig. 1 D were shifted to YES containing LatA (time 0) and examined by RFP-Bgs1 and CW fluorescence time-lapse video microscopy. Arrows, loss of Bgs1 ring and spreading of Bgs1; white arrowheads, septum rudiment; blue arrowhead, septum completion; dashed rectangles, septum area shown in the time-lapse sequences of CW series. Scale bars = 5 μm. (E) TEM ultrastructure of control septa formed in cells without LatA treatment. Both open and complete septa present the typical three-layered structure of PS and SS. Cells were grown as in A without LatA and analyzed by TEM. Line points inside the PS and SS. Scale bars = 2 μm. (F) Ultrastructure of the lateral cell wall depositions (arrows) generated from non-ingressing septum rudiments without F-actin. Cells were grown as in A with LatA and analyzed by TEM. Scale bars = 2 μm. (G) Model of septum rudiment arrest and the ensuing lateral deposition of cell wall in the absence of F-actin. LatA treatment causes the blockage of slow-ingressing rudiments (phase 1, <0.30 µm in length) and Bgs1, Bgs4, and Ags1 spreading all over the plasma membrane, forming ICWs. GS, glucan synthase. Error bars show SD.

F-actin is essential for the ingression of incipient septum rudiments. (A) Septation in cells treated with LatA. All the open septa (open arrowheads) except septum rudiments (arrows) progress to completion (closed arrowheads) in cells grown in the presence of LatA. Cells grown as in Fig. 1 D were shifted to YES containing LatA (100 µM; time 0) and analyzed by CW fluorescence microscopy. Scale bar = 5 μm. (B) The percentage of cells with septa divided into different length intervals as indicated was quantified in CW-stained cells as in A. After a long LatA treatment (1 h), most cells displayed either septum rudiments or complete septa (n = 1,077 septa). (C) LatA treatment in cells with septum rudiments causes Bgs1, Bgs4, and Ags1 glucan synthase spreading, forming large lateral bands (arrows). Cells were grown as in A and simultaneously analyzed by RFP, GFP, and CW fluorescence microscopy after 15 min with LatA. Scale bar = 2 μm. (D) Time-lapse sequences from incipient septation to completion in the absence of LatA (top panel) or from incipient septation to ingression arrest and spreading of Bgs1 in the presence of LatA (middle and bottom panels). Cells grown as in Fig. 1 D were shifted to YES containing LatA (time 0) and examined by RFP-Bgs1 and CW fluorescence time-lapse video microscopy. Arrows, loss of Bgs1 ring and spreading of Bgs1; white arrowheads, septum rudiment; blue arrowhead, septum completion; dashed rectangles, septum area shown in the time-lapse sequences of CW series. Scale bars = 5 μm. (E) TEM ultrastructure of control septa formed in cells without LatA treatment. Both open and complete septa present the typical three-layered structure of PS and SS. Cells were grown as in A without LatA and analyzed by TEM. Line points inside the PS and SS. Scale bars = 2 μm. (F) Ultrastructure of the lateral cell wall depositions (arrows) generated from non-ingressing septum rudiments without F-actin. Cells were grown as in A with LatA and analyzed by TEM. Scale bars = 2 μm. (G) Model of septum rudiment arrest and the ensuing lateral deposition of cell wall in the absence of F-actin. LatA treatment causes the blockage of slow-ingressing rudiments (phase 1, <0.30 µm in length) and Bgs1, Bgs4, and Ags1 spreading all over the plasma membrane, forming ICWs. GS, glucan synthase. Error bars show SD.

This Feature Is Available To Subscribers Only

or Create an Account

Close Modal
Close Modal