OVEREXPRESSION OF WUSCHEL IMPROVES THE INDUCTION OF EMBRYOGENIC CALLUS IN SCALPS OF MUSA ACUMINATA L. AAA, CV. “GRAND NAIN”

Abstract

Background: During the last few years the home box transcription factor WUSCHEL (WUS) has been shown to cause dedifferentiation when expressed on somatic cells followed by a production of new stem cells that can lead to somatic embryogenesis or organogenesis. WUS has been shown to promote the transition from a vegetative to an embryogenic state when overexpressed. Objective/Hypothesis. The genetic in vitro transformation of meristematic tissue of Musa acuminata L. AAA, cv. “Grand Nain” was carried out using a heterologous gene WUSCHEL from Arabidopsis thaliana, via vacuum infiltration with Agrobacterium tumefaciens, to establish and ascertain if its expression modifies the progression of the explants to the embryogenesis process and or reduces the time needed for in vitro embryogenic induction phase. Methodology: Explants of proliferating shoot meristems, named “scalps”, of Musa acuminata L. AAA, cv. “Grand Nain” was transformed with WUS gene under the control of promoter GAL4, inducible by 17b-estradiol. The effect of steroid 17b-estradiol (b-Est) and homobrassinolide (HomoBra) on the in vitro somatic embryogenesis induction phase of non-transformed banana scalps was investigated. Results: The successful transformation of the explants was confirmed by PCR, for the transferred neomycin phosphotransferase II (NPTII) and the WUS gene. In addition, the expression of the red fluorescent protein (RFP) for the corresponding transferred reporter gene was verified by fluorescence microscopy in proliferated transformed tissues. Besides, the transformed tissue response to the induction of embryogenesis with either b-Est and/or HomoBra, inducers of the transgene were investigated. Implications: The improvement of the process of somatic embryogenesis in this way, generates a more effective and productive study model in a short time. Conclusions: WUS can promote the meristematic tissue-to-embryonic transition, and eventually somatic embryo formation, suggesting that the homeodomain protein can play a critical role during embryogenesis.