MOLECULAR ASPECTS OF NUCLEAR GENOME INVOLVEMENT IN S CYTOPLASMIC MALE-STERILE MAIZE.

摘要

The nuclear genome genetically influences the S-type of cytoplasmically inherited male sterility in maize (cms-S) at three levels: (1) nuclear fertility restoring genes; (2) the degree of instability, i.e., the frequency of reversion to fertility; and (3) the proportion of revertants which are due to either nuclear or cytoplasmically based mutations. At the molecular level, this thesis project asked if the linear, plasmid-like mitochondrial DNAs (plmtDNAs) S1 and S2, unique to plants carrying cms-S cytoplasms, are involved in the nuclear control phenomenon. Levels of S1 and S2 plmtDNAs were assayed electrophoretically and shown to have differing replication characteristics in different inbred backgrounds, irregardless of the cms-S cytoplasmic strain. Shifts in relative levels of S1 and S2 were observed as nuclear genomes converted during backcross programs.;The presence of S2 plmtDNA sequences in nuclear DNA was assayed in lines in which nuclear based reversions to fertility occur, using the techniques of Southern filter hybridization with genomic DNA restriction digests and in situ cytological nucleic acid hybridizations. Non-mtDNA hybridization bands in the genomic blots and putative chromosomal hybridization sites for S2 were observed and suggest a means of communication between organelles at the DNA level. Complications arose from the presence of mtDNA sequences during hybridization analyses so that confirmation of these results will require supplementary methods which are most discriminatory.