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evident by 1983 that the Agrobacteriuni IS a sure candidate for genetic trallsformation
(Chilton, 1983; Herrera-Estrella et al., 1983). Where T-DNA of the Ti plasm~d call be
--. . .
transferred to the plant cells and that can servr. as an cxcelle~lt tool for the genetic
transformation of plants by dlsarnming the T-DNA and introducing the genes of interest into
that area.
2.1.2.2 Molecl~lnr ~nccl~a~~is~~~
of T-DNA Ir:~~~sfcr illto pla~~ts
Tlis dlrtails of tliesc ~nechanisms can be obta~ned from scveral ~revicws (Hooykans
and Schilperoot, 1992; Zambryski, 1992; Grcene and Zambryski, 1993; Zupan and
Zambtysk~, 1995). Wirlatls (1992) provided a critical review of chenlical signaling between
Agrobacirriu~~i and plants cells. .
2.1.2.3 Tools for ge~letic tl.ansformatio~~ /
Understanding the plant gene structure and its essential components is n
prerequisite for dcsig~~iny the tools for gellctic transformation. By the time the coilcept~~nl
basis fbr the genctlc transfonnation was ready using Aprubaclei~iu~~i, the components of a
complete plant gclie to be effcctivcly exl~resscd was also ready. The ainalgamation of
various niolecular biology tech~iiques led to the dcs~gning of vectors for transforming the
plant cells.
i
Tru~s/orrnuiio~~ vectors: Most widely used vectors are binary vectors (Bevan,
1984) and cointegrate type vectors (Draper el al., 1988; Rogers ct al., 1987; Deblaere et al.,
1987). The co~ntegrate type vectors have bccoiile less popular since they are more difficult
to engineer than binary type ones and are less efticiel~t.