Hairy Root Cultures and Plant Regeneration in <i>Solidago nemoralis</i> Transformed with <i>Agrobacterium rhizogenes</i>

Abstract

By screening a native plant extract library we identified Solidago nemoralis as a novel source of agonists for alpha7 nicotinic receptors for acetylcholine with therapeutic potential. The next phase of our drug discovery strategy is to in crease the yields of active compounds in the plant species by gain of function mutations in hairy root cultures [1]. Here we report a protocol for Agrobacterium rhizogenes- mediated genetic transformation of hairy root cultures of Solidago nemoralis which will enable this . Leaf explants of this species were successfully transformed with a frequency of 30% - 35% using A. rhizogenes strain R1000 harboring the binary vector pCambia 1301. Transformation was confirmed using the β -glucuronidase (GUS) histochemical assay. Transformed hairy roots showed spontaneous regeneration of adventi tious shoots in media without the addition of cytokines, albeit at very low frequency. However, media supplementation with auxin ( α -naphthaleneacetic acid, NAA) increased shoot regeneration frequency to 35% and resulted in viable ad ventitious shoots. Transformation was confirmed at all phases of plant regeneration by GUS staining. Hairy root trans formation of Solidago altissima has been previously reported, but this is the first report of genetic transformation of S. nemoralis . The protocol will allow for a large population of activation tagged mutants of S. nemoralis to be generated which will be then screened for the presence of stable mutants which are over-producing metabolites with activity at alpha7 nicotinic receptors. These over-producing mutant cultures will then be regenerated into intact mutant plants.