Genomic incompatibility

Genotype had a pronounced effect on the Riobisco activity, however, none of the hybrids exceeded the activity measured for PDH40 (Table 1.). The parental chloroplast type, as such, did not influence the Rubisco activity, however, our results indicated that Rubisco activity was affected by nuclear-organelle genome incompatibility. At the tetraploid level the most affected hybrid had tuberosum cpDNA. Among the hexaploid hybrids the parental nuclear dosage effect supported the incompatibility hypothesis. 

Hosaka, K., Hanneman, R. E. Jr. (1998b). Genetics of self-compatibility in a self-incompatible wild diploid potato speeies Solanum ehaeoense. 2. Localization of an S locus inhibitor (Sli) gene on the potato genome using DNA markers. Euphytica, 103, 256-271. 

It was earlier hypothesized that the AAC had been invented either by chlamydiae with subsequent LGT to rickettsiae or by rickettsiae, and was physically but not functionally transferred from the latter to the genome of an amitochondriate host. Similarly to Coxl, also containing 12 transmembrane domains incompatible with import, rickettsial AAC could not be imported into mitochondria, but was later recruited to chloroplasts in a plant lineage (Emelyanov 2001b). Therefore, unrelated mitochondrial AAC - a member of the mitochondrial carrier family proteins containing six transmembrane... 

If one examines the pattern of proteins synthesized in cells infected for three to four hours with a picomavirus, the only proteins synthesized are viral, for by this time the synthesis of most host proteins has ceased. In the earliest studies carried out by Summers et al. (I4) in poliovirus-infected HeLa cells, about I4 different virus-specified polypeptides were identified by SDS-polyacrylamide gel electrophoresis. The net mass of these viral polypeptides, however, exceeded the coding capacity of the viral genome by a factor of 2. This finding was incompatible with what was then known about the translation of the small RNA bacteriophages such as Q6 and R17 In these cases, each of the three cistrons was found to have its own initiation and termination signals (15) ... 

The viability of these hybrid cells permits an inference of interest from both the embryological and evolutionary points of view. The continuous multiplication and apparent permanence of hybrids between somatic cells of species phylogenetically as remote as the hamster, the rat, and the mouse, shows that, between somatic cells, there is no incompatibility similar to that observed in sexual interspecific crosses. It will be recalled that this incompatibility, in the extreme cases, results in the elimination of the foreign chromatin from the fertilized egg. It is clear therefore that the inviabiUty of sexual hybrids between remote forms, when they do contain both parental genomes, is due to their inadequacy for directing development and differentiation rather than to the inability of hybrid genotypes to control the balanced metabolism involved in cell replication. 

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