Director, NIH 
- 2 - 
November 21, 1977 
assumptions seem to be consistent with the wording of the Introduction 
of the proposed revision, but the proposed revision also requires 
specific exclusion of recombinant DNAs not considered novel. My 
interpretations and the required exclusions would place a nearly 
impossible burden on the Director and the Recombinant DNA Molecular 
Program Advisory Committee if such a list of combinations of DNAs 
is actually prepared. 
Certification of Host-Vector Systems . To explore applications 
of recombinant DNA technology in plants requires the development of 
useful host-vector systems. The vector concept implies a genetic 
element that can transmit a fragment of foreign DNA and direct its 
replication. To develop a host-vector system for novel recombinant 
DNA, the proposed revision requires one to determine with which 
organism the host normally exchanges genetic information, with 
which organisms the vector exchanges genetic information, and what 
sort of information is exchanged before that host-vector system can 
be employed in recombinant DNA research. These tasks required for 
certification will be simplified and the answers determined with 
greater precision if recombinant DNAs not considered novel (according 
to the previous discussion) are employed and results analyzed with 
molecular probes. Furthermore, the section of the proposed revision 
of the Environmental Guidelines dealing with plant host-vector 
systems allows certain vectors to be employed for transfer of 
recombinant DNA to host plant material under P2 and P3 levels of 
containment. In the same section, the proposed revision provides 
for a reduction of containment level if hosts such as undifferentiated 
plant cells in culture are employed. I assume that the studies 
contemplated in these sections are restricted to certified host- 
vector systems. 
Forbidden Experiments . Under the section of the Experimental 
Guidelines dealing with plant host-vector systems, "whole plants or 
plant parts that cannot be adequately contained" are restricted. I 
cannot determine whether the intent is to forbid experiments with 
whole plants or to forb’id experiments with whole plants that cannot 
be adequately contained. I assume the latter interpretation is 
consistent with the intent because elsewhere in the same section, 
the quidelines implies that plant parts or whole mature plants of 
small species (e.g., Arabidopsis ) can be adequately contained. 
This interpretation raises yet another question. No matter how 
large the species in question may normally become, it can be used 
experimentally as a small plantlet or seedling. I raise, this 
question because embryogenesis from suspension culture is a rapidly 
evolving technique that might usefully be employed to determine the 
effect of recombinant DNA on plant hosts. The normal size of the 
plant species is relatively unimportant because the experiment can 
be terminated at any time physical requirements for containment 
dictate. 
Modified Viruses . In much of the work one might presently 
contemplate, the vector would be a recombinant DNA formed from an 
infectious viral genome. I assume that such a vector would be 
considered a modified virus. 
[Appendix A — 79] 
