Evaluation of Factors Affecting Direct Organogenesis in a Somatic Tissue Culture of Sinningia speciosa (Lodd.) Hiern

In this study, the influence of genotype, concentration of thidiazuron (TDZ), and explant position on the culture medium in organogenesis in a somatic tissue culture of two gloxinia cultivars was investigated. Isolated explants cultured on the medium containing TDZ formed adventitious shoots directly without an intervening callus phase. Explant regeneration frequency varied depending on the genotype, TDZ concentration, and explant position on the medium. The analysis of variance revealed that cultivar (C), TDZ concentration (T), position of explant on culture medium (P), and the interaction of C × T, C × P, T × P, and C × T × P significantly influenced the frequency of shoot formation. However, the effect of interface C × P and C × T × P on the number of shoots per explant was not significant. “Snowy” leaf explants manifested a significantly higher mean shoot formation frequency (p ˂ 0.01) in comparison with the cultivar “Midnight Purple”. The medium enriched with 3.5 μM TDZ resulted in the highest organogenesis frequency, while the highest shoot number per explant was acquired on medium supplemented with 4.0 μM TDZ. The explants of the tested cultivars cultured on the medium with the adaxial side down showed a significantly higher (p ˂ 0.01) shoot formation frequency in comparison with explants cultured on the medium with the abaxial side, and they showed a higher mean number of shoots per explant. An effective method for in vitro organogenesis of Sinningia speciosa (Lodd.) Hiern without an intervening callus phase was established.

Rapid, Stabilizing Palindrome Rearrangements in Somatic Cells by the Center-Break Mechanism

ABSTRACT DNA palindromes are associated with rearrangement in a variety of organisms. A unique opportunity to examine the impact of a long palindrome in mammals is afforded by the Line 78 strain of mice. Previously it was found that the transgene in Line 78 is likely to be palindromic and that the symmetry of the transgene was responsible for a high level of germ line instability. Here we prove that Line 78 mice harbor a true 15.4-kb palindrome, and through the establishment of cell lines from Line 78 mice we have shown that the palindrome rearranges at the impressive rate of about 0.5% per population doubling. The rearrangements observed to arise from rapid palindrome modification are consistent with a center-break mechanism where double-strand breaks, created through hairpin nicking of an extruded cruciform, are imprecisely rejoined, thus introducing deletions at the palindrome center. Significantly, palindrome rearrangements in somatic tissue culture cells almost completely mirrored the structures generated in vivo in the mouse germ line. The close correspondence between germ line and somatic events indicates the possibility that center-break modification of palindromes is an important mechanism for preventing mutation in both contexts. Permanent cell lines carrying a verified palindrome provide an essential tool for future mechanistic analyses into the consequences of palindromy in the mammalian genome.

RESISTANCE RESPONSES OF PLANTS REGENERATED FROM TOMATO ANTHER AND SOMATIC TISSUE CULTURES TO CLAVIBACTER MICHIGANENSE SUBSP. MICHIGANENSE

The production of gametoclonal and somaclonal variants in tomato is of great importance for the genetic improvement of tomato hybrids and cultivars. The possibility to obtain tomato plants resistant to Clavibacter michiganense subsp. michiganense (Cmm) through anther and tissue culture was investigated in the present study. Regenerants from anther and tissue cultures and their progenies (R1-R3) in the cultivars Roma ms and Bella, lines L. 24–13, and L. 6944, as well as the hybrids Roma ms × UC 82A, Roma ms × L. 31, Roma ms × Bella, and Cristy, were tested for resistance to Cmm. The regenerants differed in their resistance to Cmm. All regenerants from the anther culture of the genotype Roma ms and Roma ms × UC 82A are susceptible to the disease, while those from Bella and Roma ms × L. 31 vary from susceptible to resistant. The highest number of regenerants obtained from somatic tissue culture lacking disease symptoms until the end of the vegetation was observed in the genotypes Cristy and L. 24–13. Variation in regenerant resistance is found in R1, Rb, and R3. The results suggest that the gametoclonal and somaclonal variation may be efficiently applied to obtain tomato plants resistant to Cmm.

Variations in long-term wheat somatic tissue culture

Morphological and chromosomal changes were induced among plants regenerated from wheat somatic embryogenic tissues that retain regenerative potential for a long time. An effect of in vitro culture on mitochondrial DNA was also ascertained since variations in mitochrondrial DNA were observed in embryogenic and nonembryogenic genotypes. These variations were detected on restriction patterns. The possible significance of the mtDNA variations in affecting plant fertility and regeneration ability is discussed.