Agrobacteria carrying mutations at the auxin-biosynthesizing loci (iaaH and iaaM of the Ti plasmid) induce shoot-forming tumors on many plant species. In some cases, e.g. Nicotiana glutinosa L., tumors induced by such mutant strains exhibit an unorganized and fully autonomous phenotype. These characteristics are stable in culture at both the tissue and cellular level. We demonstrate that the cytokinin-biosynthesis gene (ipt) of the Ti plasmid is responsble for the induction of both auxin and cytokinin autonomy in N. glutinosa. Cloned cell lines carrying an ipt gene but lacking iaaH and iaaM are capable of accumulating indole-3-acetic acid. Interestingly, non-transformed N. glutinosa tissues exhibit an auxin-requiring phenotype when they are grown on medium supplemented with an exogenous supply of cytokinin. These results strongly indicate that exogenously supplied cytokinin does not mimic all the effects of the expression of the ipt gene in causing the auxin-autonomous growth of N. glutinosa cells.

Extraction of RNA from Tetrahymena mitochondrial ribosomes yields several RNA species, including a "large" 21S molecule, a "small" 14S molecule, a 7S molecule, and other smaller RNAs. The molecular weight of the 14S rRNA indicates that it is about 1,300 bases in length. We have sequenced the 14S rRNA gene and, by aligning our sequence with that of the corresponding small rRNA from E. coli, find that the 14S rDNA is at least 1,635 bases in length. We propose, based on the results of hybridization studies, that this unexpected length is due to the presence of 7S RNA sequence within the 14S gene sequence. The 7S region is apparently lost from the 14S rRNA, yet is still a component of the ribosome.

An experiment was conducted to determine the types, extent, and heritability of new phenotypic variants recovered from carrot cell cultures initiated from mature tap-root explants of the male-fertile carrot (Daucus carota L.) `Slendero'. Embryogenic callus was transferred to plant-growth-regulator-free medium 66 days after culture initiation, and regenerated plantlets were harvested and eventually planted in a field. The tap roots of mature regenerated plants were vernalized at 5C for 9 weeks and replanted. Of 31 flowering regenerants, 25 exhibited some form of petaloid male sterility; the remaining six regenerants were male fertile. All plants from the same original explant were either all sterile or all fertile. Three generations of sterile regenerant × petaloid cytoplasmic male sterility (CMS) maintainer (M) progeny tests showed that the new CMS behaved in a similar manner to that previously reported. Comparison of mitochondrial DNA restriction patterns of sterile and fertile regenerants with those of `Slendero', petaloid CMS, petaloid M, and brown anther CMS lines resulted in the following conclusions: 1) the sterile regenerants exhibited patterns identical to the known petaloid CMS and 2) the fertile regenerants were different from the original `Slendero' and the sterile regenerants and nearly identical to a known petaloid CMS M line. The high frequency of CMS among regenerants from `Slendero' carrot cell cultures may provide an efficient method to develop sterile M tandem lines and corresponding new hybrid varieties.