Somaclonal Variation in the Gliadin Patterns of Grains of Regenerated Wheat Plants

Maddock, S. E., Risiott, R., Parmar, S., Jones, M. G. K. andShewry, P. R. 1985. Somaclonal variation in the gliadin patternsof grains of regenerated wheat plants.—J. exp. Bot. 36:1976–1984. The banding patterns of the gliadin storageproteins of the grains of 590 regenerated plants from six wheatcultivars were examined by polyacrylamide gel electrophoresisusing lactate buffer. Variation additional to that present incontrol material was observed at a low frequency (1%). Two variantlines showed extensive changes in banding patterns which wereaccompanied by morphological variation of the plants. More limitedvariation in the form of an extra –gliadin band was observedin a third line. Differences in the seed gliadins were not foundin four lines which had shown stable phenotypic changes in heightin field trials. Key words: Wheat, somaclonal variation, gliadins, tissue culture, seed proteins     

Regulation of Rubisco by inhibitors in the light

2-carboxy-D-arabinitol-1-phosphate (CA1P) bound to Rubisco either in leaf extracts or after purification can be displaced by SO₄^2? ions. Thus, treatment of leaf extracts with a buffer containing 200 mol m^?3 SO₄^2? displaces any bound CA1P and enables measurement of maximum car-boxylation potential. In tobacco leaves, the activity following treatment with SO₄^?2 ions (‘maximal activity’) is greater than the total Rubisco activity. The ratio of the two activities altered in a dynamic way with fluctuations in irradiance. Even in species which do not produce significant amounts of CA1P, the maximal activity greatly exceeded the total activity. Anion exchange separation of components in acid extracts confirmed the absence of CA1P in tobacco leaves harvested above an irradiance of 300 μmol quanta m^?2 s^?1, but the presence of another inhibitor of Rubisco. These results are consistent with the regulation of Rubisco activity by inhibitors other than CA1P which, like CA1P, can be displaced by SO₄^2? ions.     

Identification of dry-pinned museum specimens of the sibling species Anopheles gambiae and An.arabiensis (Diptera: Culicidae) using non-radioactively labelled DNA probes

Non-radioactively labelled DNA probes were tested for their ability to identify dried museum specimens of Anopheles gambiae and its sibling species An.arabiensis . The specimens were the progeny of wild-caught females collected in 1991 from villages in western Kenya. Three years later, specimens whose identity was known to the second author were provided 'blind' to the first author for identification with oligonucleotide probes (SH 5 and SH 4 derived from pAngss and pAngsl, respectively) using a simplified squash-blotting protocol for non-radioactive probes. All specimens were successfully identified with whole-body squashes, and the results agreed with previous identifications of parents or siblings based on rDNA-polymerase chain reaction . The amounts of DNA released by squash-blotting were just sufficient for identification by those experienced in the technique, but not for squashes of heads or thoraces alone. An aim of the study was to determine whether squash-blot methods of identification might be useful for establishing the genetic identity of name-bearing type specimens of sibling species held in museum collections.     

The Effect of Boron and Gibberellic Acid on the Senescence of Leaf Discs from Lycopersicon esculentum cv. Rutgers

When leaf discs of Lycopersicon esculentum Mill. cv. Rutgers were floated on solutions containing 4.33 × 10^–6 M gibberellic acid (GA₃), 1.0 ×x 10^–6M boron (B), separately and together, senescence was retarded with respect to controls. Degradation of chlorophyll, total protein, RNA, and DNA was delayed, and decreases in fresh weight and leaf disc diameter checked. The loss of chlorophyll, protein, RNA, DNA, fresh weight, and diameter were 10, 20, 30, 8, 28, and 0 per cent with GA₃ alone; 15, 25, 35, 8, 31, and 0 per cent with B alone; 8, 14, 25, 7, 25, and 0 per cent with GA₃ plus B; contrasted with 50, 40, 50, 9, 42, and 3 per cent for the controls. An analysis of variance was performed on all data except for disc diameter. All sources of variance were significantly or highly significant at the 1 per cent level except for the effect of boron on DNA level, which was significant only at the 2.5 per cent level. Retardation of senescence by GA₃ may be associated with the known ability of GA₃ to stimulate m-RNA and protein synthesis. The effect of boron may be due to an effect on sugar and starch balance, translocation of sugar, or on water balance, but more likely boron plays a role in nucleotide and protein metabolism in plants. Boron may be involved in the synthesis of DNA, a role perhaps mediated by GA₃.