Fig. 1.

Lateral haustorium structure at different developmental stages of Phtheirospermumjaponicum. (A) Developmental stages of the xylem bridge were classified into three categories: SI, pre-initiation; SII, developing; and SIII, fully connected. (B) Ratio of each developmental stage at the indicated time point. n=21∼26 for each time point. (C-E) Longitudinal sections of haustorium at the indicated time point. Blue broken lines delineate the layer of indicated cell types: epi, epidermis; cor, cortex; endo, endodermis; peri, pericycle. Sections were stained with Safranin-O. (F) Magnified view of the interface region of the haustorium indicated in E. Black asterisks indicate intrusive cells. (G-K) Expression pattern of the AtCYCB1;2 promoter in the P. japonicum root meristematic region (G) and differentiated region (H) before haustorium formation, and during haustorium development at the indicated time points (I-K). Six out of eight hairy roots showed a similar expression pattern. The same haustorium is shown in I-K. Two haustoria developed in close proximity, indicated by white arrows. White asterisks denote intrusive cells. YFP fluorescence is in yellow. Bright-field and YFP fluorescent images are merged. Scale bars: 100 μm in A,G-K, 50 μm in C-E, 20 μm in F. Pj, P. japonicum root; At, Arabidopsis thaliana root.