Abstract
Haustorium development in C. japonica can be induced by cytokinin (CK) or by far-red light (FR) with contact stimuli. Our previous data on expression patterns of Cuscuta response regulator genes (CjRRs) during the haustorium induction strongly suggested an increase of the endogenous CK level in FR-irradiated Cuscuta. In this study, to inquire the occurrence of de novo synthesis of CK following FR irradiation, a cDNA clone of isopentenyltransferase gene (CjIPT) was isolated and its expression levels were monitored. Following FR irradiation, although expressions of CjRRs were induced within two hours, CjIPT transcripts could not be detected until twelve hours, demonstrating that the CjIPT cloned here does not involve in the increase of cytokinin level responsible for an enhancement of CjRR expression. This is supported by the observation that the CjRR expressions were induced in Cuscuta which had been treated with cycloheximide (100μM, 3 hours), followed by FR irradiation.
