AGROBACTERIUM RHIZOGENES-MEDIATED TRANSFORMATION AND REGENERATION OF THE LEGUME ASTRAGALUS-SINICUS (CHINESE MILK VETCH)

A system for the Agrobacterium rhizogenes-mediated transformation and root and then shoot regeneration of the legume species Astragalus sini cus (Chinese milk vetch) has been developed. A. rhizogenes DC-AR2 stra in harboring the binary vector pBI121, carrying the uidA gene encoding GUS activity, was used to transform seedlings in wound sites. Transfo rmation was monitored by detection of mikimopine and histochemical bet a-glucuronidase (GUS) activity. GUS expression was found in approximat ely 44% of the seedlings 15 days after infection and 46% of the aerial roots tested were GUS positive while all of the GUS positive roots al so contained mikimopine, which is a characteristic of strain DC-AR2. W hen the transformed roots were cultured in vitro, sporadic shoot devel opment occurred after culture periods ranging from 1 to 2 months and t ransgenic A. sinicus plantlets were established. The transformation of the regenerated plantlets was further confirmed by histochemical GUS activity and by Southern blot analysis. The resulting plants exhibited the 'Ri plasmid' syndrome such as small thin leaves and short interno des while cultured roots grew rapidly and were plagiotropic. This tran sformation and plant regeneration system will be useful as a model sys tem for testing the expression of genes and their effect on a legumino us plant. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.