EXPRESSION OF THE MOVEMENT PROTEIN OF TOBACCO MOSAIC-VIRUS IN THE CYANOBACTERIUM ANABAENA SP STRAIN PCC-7120

The movement protein (MP) of tobacco mosaic virus (TMV) alters the str ucture and function of the plasmodesmata, the intercellular communicat ion channels in plants. cDNA encoding the TMV MP was cloned in a cyano bacterial shuttle vector and transferred to Anabaena sp. strain PCC 71 20. MP was synthesized in Anabaena sp. strain PCC 7120 from the tac pr omoter and was induced severalfold by addition of the lac inducer IPTG . Immunoblot analysis of subcellular fractions obtained from IPTG-indu ced vegetative cells indicated that MP was highly enriched in the cell wall and the cytoplasmic membrane fractions. High level of MP express ion prevented diazotrophic growth and new heterocyst differentiation i n cultures of Anabaena sp. strain PCC 7120. Although expression of MP in undifferentiated filaments did not inhibit growth, these filaments could not form heterocysts when subsequently deprived of combined nitr ogen. Wild-type cells or cells containing the shuttle vector lacking t he MP gene grew normally and differentiated heterocysts in the presenc e of IPTG. These results are consistent with the idea that interaction of MP with components in the cells of Anabaena sp. strain PCC 7120 pe rturbs normal cell-to-cell communication in the filaments, thereby pre venting heterocyst differentiation and diazotrophic growth.