Figure 9.

CYCB1;1::GUS (A), DR5::GUS (B) and ARR5::GUS (C) expression in the shoots and roots of control and VOC-exposed Arabidopsis seedlings after 7 days of co-cultivation with Serendipita in split plates. Results are shown for Serendipita isolate 30; identical responses were recorded with S. indica and S. williamsii. The panels on the right display details on the GUS activity in lateral root tips (1 and 2) and in newly emerging lateral roots (3) or newly established lateral root primordia (4). Compared to the corresponding controls, GUS expression in the VOC-treated shoots was stronger and expanded only for ARR5::GUS, showing activity in the rosette leaves, aside from expression in the shoot apical meristem. With regard to the VOC-exposed root system, a higher and more extensive staining as compared to the control was observed in the root tips of all three reporter lines (see insets 1 and 2) and in the developing lateral roots/primordia of the CYCB1;1::GUS and DR5::GUS seedlings (see insets 3 and 4 in A, B). ARR5::GUS expression was weak or absent in lateral root initiation sites in treated (and non-treated) plants (see inset 3 in C), but large areas of the pericycle were activated in several parts of the root system upon VOC exposure (see inset 4 in C). Scale bars = 5 mm for the overview pictures on the left and 200 µm for the zooms on the right.