Steve Topletz <[EMAIL PROTECTED]> spaketh thusly: >Antibiotics are to my knowledge extremely phytotoxic, more >toxic to the plant than to the organism.
Most are, yes. We routinely use kanamycin for transgenic selection (neomycin phosphotransferase expression using nptII). We also use bialaphos (a tripeptide antibiotic that is also a pretty darned good herbicide) with resistance conferred from the Bah protein in Streptomyces hygroscopicus; hygromycin phosphotransferase (hpt); gentamycin acetyltransferase (accC3); bleomycin resistance; and blah blah blah. The trick is that since plants normally die in the presence of the antibiotic, if we "install" a gene of interest, and it is linked to antibiotic resistance, then only successfully transformed plants will survive in the presence of the antibiotic. Look for the first generation of transgenic phals to hit the shelf to be resistant to kan or whatever. In fact, I wouldn't consider it unlikely that orchid judging someday may require some form of leaf testing for the presence of selectable markers. Remember, you read it here first. (That'll work until the marker genes can be removed, or something like the mannose-6-phosphate system come online, making antibiotic selection less useful.) However, there are two that stand out in that they are not sufficiently phytotoxic that they may be employed to rid cultures of the agrobacterium that are used for transformation: carbenicillin, and Timentin (ticarcillin + clavulanic acid). The former runs $15 a gram from PhytoTech, the second runs about $22 a gram. We routinely use several hundred mg/L of carb or tim in media with no untoward effects versus a control. OTOH, 1-2 mg/L of bialaphos kills just about everything, and 4+ mg/L is invariably lethal unless transformation has been successful. Whether either would actually do any good in mature plants, I don't know. Tissue penetration may not be sufficient. Cheers, -AJHicks Chandler, AZ _______________________________________________ the OrchidGuide Digest (OGD) [EMAIL PROTECTED] http://lists.orchidguide.com/mailman/listinfo/orchids
