Poster: Hormone synthesis & metabolism

Abs # 468: Ethylene-regulated expression of the ipt gene increases flower number in transgenic Dendranthema x grandiflorum.

Presenter:	Khodakovskaya, Mariya V, Mar.Khod@uconn.edu
Authors	Khodakovskaya, Mariya V (A)   McAvoy, Richard  (A)   Liu, Hong  (A)   Li, Yi  (A)
Affiliations:	(A): University of Connecticut

Cytokinins play an important role in regulating plant growth and development. The cytokinin gene, isopentenyl transferase (ipt), was placed under the control of an ethylene-regulated promoter and introduced into Dendranthema x grandiflorum (chrysanthemum cv. Iridon). Transformants were confirmed by PCR and Southern blot, and analyzed for phenomic response under both greenhouse and growth chamber conditions. Transgenic plants displayed a number of altered phenotypes in both greenhouse and growth chamber studies. While some transgenic lines appeared similar to the non-transgenic wild-type cultivar, others displayed dramatic increases in lateral branching development and developed shorter internodes. Most of the transgenic lines showed an increase in flower bud initiation ranging from 2 to 10-fold compare with wild-type plant. It was possible to select lines characterized by normal chrysanthemum shoot morphology but displaying dramatic increasing of flower bud number. Analysis of ipt expression (RT-PCR) revealed a correlative increase in ipt expression as phenomic response became more extreme. Isolated leaves of ethylene regulated promoter-ipt transgenic tobacco plants remained healthy and green after 20 days of dark incubation at 25oC and showed a significantly prolonged retention of chlorophyll. Leaves of non-transformed plants yellowed and senesced under the same storage regime. This unique genetic construct appears to have potential use for crop improvement in ornamental species by altering branching habit and increases flower bud initiation.