RIBOSOMAL-RNA GENES OF PHASEOLUS-COCCINEUS - V - RELATIONSHIP BETWEENRDNA PHENOTYPE AND SOMATIC DIFFERENTIATION

Size variations in the intergenic spacer of ribosomal DNA were detecte d between individual plants of openly pollinated Phaseolus coccineus. Eleven days after sowing, two plant samples were examined: slowly deve loping plants with a length less than 40 cm; and fast developing plant s with a length greater than 70 cm. The two samples were characterized by different plant weight and, at maturity, by highly distinctive see d yield. They also exhibited distinct patterns of protein expression a s analyzed by 2-D electrophoresis. In particular a 38 kDa protein, rel ated to malate dehydrogenase on the basis of its N-terminal sequence, was present at higher concentration and higher activity levels in fast developing plants. Intergenic spacer length variants were detected in both samples at approximately 180 bp intervals. More than one spacer length variant was present in each individual plant. At least 13 diffe rent intergenic spae er hybridization patterns were in fact detected: some patterns occurred equally in both slowly and fast developing samp les while the majority of patterns was significantly different between the two samples.