Figure 2.

Regulation of phloem-conducting cell differentiation in haustoria of Cuscuta japonica. (A) Expression profile of CjNEN4 in haustoria. Expression level increased from 72 to 96 h.a.a., which is inconsistent with the retention of nuclei. Expression levels were normalized by that of C. japonica ribosome protein S18 gene (CjRPS18). Mean and standard error of three biological replicates are indicated. (B) Hypothesis for the regulation of differentiation and enucleation of phloem-conducting cells. Main hypothesis is that OPS-BIN2-BES1 regulatory pathway may promote the enucleation by controlling APL-NAC45/86-NEN regulatory pathway, although the point of action has not been identified (dotted arrow). In Cj haustoria, expression of OPS, BIN2, or BES1 may be lower than conventional vascular tissues, which results in retention of nuclei in phloem-conducting cells.