Fig. 1: The importance of subapical cells for hyphal growth.

a Hyphae of T. reesei, expressing TrmsGFP-Sso1. Individual cells are separated by septa. Scale bar = 10 µm. b Electron micrograph showing multiple WBs “guarding” the septal pore. Scale bar = 0.5 µm. c WBs, labelled with Hex1-TrmsGFP (green), in cells expressing the plasma membrane marker TrmCherry-Sso1 (red). WBs spread around septal pores (“Open”) or locate in the centre of the septum (“Plugged”). Scale bar = 1 µm. See also Supplementary Movie 1. d Quantitative analysis of WB sealing of septal pores; red dots represent means of individual experiments. Note that almost all septa are open. Sample size n = 3 independent experiments with 14–35 septa per experiment. e Extension of a hypha over 4 min. False coloured overlay shows hyphal extension. Scale bar = 2.5 µm. f Extension of a hypha over 48 min after laser-injury of the 2^nd cell. Scale bar = 2.5 µm. g Effect of injury of subapical cells on hyphal tip growth. Hyphae that failed to seal their apical cell after laser injury or were not growing before injury were not included. Sample size n = 4 independent experiments for 2^nd and 3^rd cell and n = 3 independent experiments for 4^th, 5^th and 6^th cell with 9–22 hyphae per experiment. h Growth rate of intact (control) and injured hyphae of T. reesei. Growth was measured 45 min after laser injury. Sample size n = 181 hyphae for control n = 5 hyphae for 2^nd cell, n = 37 hyphae for 3^rd cell, n = 43 hyphae for 4^th cell, n = 48 hyphae for 5^th cell and n = 47 hyphae for 6^th cell from 3–17 independent experiments. i Bright-field image series showing retrograde motion of cytoplasm and organelles (arrowhead) after laser injury of the 2^nd cell. Note retrograde movement of cytoplasm due to leakage prior to WB-based septum sealing (open arrowhead). Scale bar = 3 µm. See also Supplementary Movie 3. j Contrast-inverted kymograph showing retrograde EE motility after laser injury of the second cell. Septum indicated by a red-dotted line; time of laser treatment indicated by green arrowhead. Horizontal scale bar = 1 µm; vertical scale bar = 3 sec. k Hyphal response to laser injury-induced cytoplasm leakage from the 1^st cell. Cytoplasm leakage is given as retrograde displacement of TrmsGFP-Rab5-labelled EEs (relative to the length of the 1^st cell). Growth of injured hyphae was measured after 45 min. Sample size n = 31(Not growing), n = 8 (Growing) and n = 13 (Dying) independent experiments. See also Supplementary Fig. 2. Results were confirmed in 3 (a, c, e, f, i, j) and 2 (b) independent experiments. Bars in (d, g) represent mean ± SEM; sample sizes are indicated; red dots represent independent experiments; some data sets in (h,k) did not pass a normality test (Shapiro-Wilk test, P > 0.05) and thus are given as Whiskers’ plots (h, blue lines: 25/75 percentiles; red line: median; minimum and maximum at whiskers ends) or as individual data points, including median and 95% confidence interval (k); statistical comparison with control in (h, k) used non-parametric Mann-Whitney testing, with *= two-tailed P-value 0.0134 (k), **= two-tailed P-values of 0.0059 (h) and ****= two-tailed P-values < 0.0001 (h). Data in (a, d–k) were obtained from growing hyphae. All data are provided in the Source Data file.