FIG. 1.

Manipulation of polarized growth in the ramosa-1 mutant. (A) Conidia obtained from the ramosa-1 and T312 strains were cultivated under controlled conditions and subjected to differential interference contrast microscopy. Pictures for at least 100 germlings were taken for each time point and the percentage of branched germlings calculated (number at upper right). Young unbranched germlings are visible for both strains after 13 h of growth at 24°C (a and b). After a temperature upshift to 37°C for 1 h, 75% of ramosa-1 germlings show apical branches (c), compared to only 5% of T312 germlings (d). For the next 3 hours at 37°C, 100% of ramosa-1 germlings developed additional apical and subapical branches (e, g, and i) before growth ceased (i). In contrast, the majority of T312 germlings grew in a polar fashion (f, h, and j). (B) Polar growth of ramosa-1 germlings corresponding to panel i resumed after the temperature was downshifted to 24°C for 3 h (a). A subsequent temperature upshift to 37°C for 1 h resulted in the formation of new apical branches (b). Septa are indicated by arrowheads. Bars, 10 μm.