Explants of Ri-transformed hairy roots of spinach can develop embryogenic calli in the absence of gibberellic acid, an essential growth regulator for induction of embryogenesis from nontransformed roots

摘要

Hairy roots of spinach (Spinacia oleracea L.) were obtained by inoculation of cotyledon explants with wild-type Agrobacterium rhizogenes A13. Integration of the transfer DNA (T-DNA) of a root-inducing (Ri) plasmid of A. rhizogenes into the plant DNA was confirmed by the polymerase chain reaction. Somatic embryogenesis from explants of hairy roots were induced even when the callus-induction (CI) medium did not contain gibberellic acid (GA(3)) which is considered to be a key growth regulator that is critical for induction of somatic embryogenesis in spinach. Proteins extracted from hairy root-derived calli and from non-transformed root-derived calli generated on medium that contained 10 muM naphthaleneacetic acid (NAA), without GA(3), were analyzed by polyacrylamide gel electrophoresis. The proteins from the former calli included appreciably higher levels of a 31-kDa basic protein (BP31) (pI=8.8) than proteins from the latter. This 31-kDa protein also accumulated in embryogenic calli derived from non-transformed roots. Somatic embryos from hairy root explants, grown on medium without growth regulators, yielded regenerated plantlets with actively growing root systems and shoots that did not bolt.