The Clerodendrum aculeatum-systemic resistance inducing (CA-SRI) protein, a 34 kDa basic protein, plays a key role in inducing strong systemic resistance in susceptible plants against various plant viruses [22]. We have cloned the cDNA encoding the CA-SRI from C. aculeatum leaves using antibodies raised against the purified protein and degenerate oligonucleotide probes derived from microsequencing of the CA-SRI protein. The full-length cDNA consisted of 1218 nucleotides with an open reading frame of 906 bp. The deduced amino acid sequence of CA-SRI protein showed varying homology (ranging from 11 to 54%) to the ribosome inactivating proteins (RIPs) from other plant species. CA-SRI inhibited in vitro protein synthesis both in rabbit reticulocyte lysate and wheat germ lysate but not in Escherichia coli in vitro translation system. The CA-SRI open reading frame was expressed in an E. coli expression vector and the purified recombinant protein inhibited protein synthesis in rabbit reticulocyte lysate. Southern blot analysis indicated that the CA-SRI gene may be present in low copy number.

In vitro produced plants were transferred to sterilized garden soil: compost (1:1) and then transferred to green house for hardening. Genetic stability of mother plant and the regenerants produced in vitro was assessed by random amplified polymorphic DNA (RAPD). In randomly selected plant material (mother plant) and its regenerants, 87 scorable bands were generated by four different primers, showing monomorphism with the mother plant. Thus, molecular analysis reveals that the micropropagation system described is a reliable method for propagation of P. lanceolata.