Mutational instability in Ulva mutabilis and its relation to different stages of the life cycle

Abstract

Studies of the mutational instability presently residing in three mutant strains of Ulva mutabilis Føyn have indicated that, (I) it has a dominant behaviour in heterozygous conditions, (II) its inheritance seems not to be that of a single mendelian factor, and (III) the degree of instability as measured by the gametes is variable and dependent on the genetic constitution of the sporophyte generation prior to the gametophytes in question.

Transformation of Ulva mutabilis (Chlorophyta) by vector plasmids integrating into the genome

“…Algal strains. The wildtype U. mutabilis Føyn strain wt-G (mtÀ) (gametophyte); ([mtÀ]; G/PS-swi + ; mut À ; RS 140 + ; RS180 + ); and its "slender" mutant sl-G(mt+)5 (gametophyte) (mt(+); Sl + ; G/PS-swi À ; mut À ; RS 140 + ; RS180 -) are direct descendants of the original isolates of B. Føyn from the South Atlantic coast of Portugal near Ohlão and Faro (Føyn 1958) [(mt(+) and mt(À): mating type; G/PS-swi: capability to switch between the gametophyte and parthenosporophyte modes of parthenogenetic propagation pathways (Hoxmark 1975) (mut: mutational instability (="mutabilis trait") Børresen 1975, Børresen andFjeld 1977); RS140 (Gen-Bank acc. no.…”

“…In later investigations, A. Fjeld and S. Børresen, however, noticed that the high mutability is not a general trait of U. mutabilis but must have resided in only one of the three original isolates collected at Olhão Børresen 1975, Børresen andFjeld 1977). While this presumably genetically instable original strain unfortunately became lost in culture, the "mutabilis trait" still survived in certain of the mutants originated by this mechanism and in their spontaneous revertants Børresen 1975, Børresen andFjeld 1977). A number of these original spontaneous developmental mutants, such as "slender" (sl), "long" (l) (Føyn 1959), "bubble" (bu) (Fjeld 1970), "lumpy" (lu) (Bryhni 1974), "slen-deroid 1" (sd1), and "slenderiod 2" (sd2) (Fjeld and Børresen 1975), are still in culture, as well as the genetically stable form of the wildtype (Fjeld 1972).…”

“…In addition, the descendants of these four plants exhibited characteristic differences in their morphology compared to the rest of the collected algae. This presumably new species was named Ulva mutabilis, because a wide variety of different developmental mutants spontaneously arose with an unusual high frequency among the offspring of these strains (Føyn 1958, 1959, Fjeld and Børresen 1975, Børresen and Fjeld 1977. In later investigations, A. Fjeld and S. Børresen, however, noticed that the high mutability is not a general trait of U. mutabilis but must have resided in only one of the three original isolates collected at Olhão Børresen 1975, Børresen andFjeld 1977).…”

“…This presumably new species was named Ulva mutabilis, because a wide variety of different developmental mutants spontaneously arose with an unusual high frequency among the offspring of these strains (Føyn 1958, 1959, Fjeld and Børresen 1975, Børresen and Fjeld 1977. In later investigations, A. Fjeld and S. Børresen, however, noticed that the high mutability is not a general trait of U. mutabilis but must have resided in only one of the three original isolates collected at Olhão Børresen 1975, Børresen andFjeld 1977). While this presumably genetically instable original strain unfortunately became lost in culture, the "mutabilis trait" still survived in certain of the mutants originated by this mechanism and in their spontaneous revertants Børresen 1975, Børresen andFjeld 1977).…”

Conspecificity of the model organism Ulva mutabilis and Ulva compressa (Ulvophyceae, Chlorophyta)

“…). The species “ U. mutabilis ” was established based on a wide range of spontaneous developmental mutants that appeared at an unusually high frequency in the offspring of the collected source material (Føyn , , Fjeld and Borresen , Børresen and Fjeld ). One noteworthy form was the ribbon‐shaped mutant named “slender,” which strongly differed from the typical and genetically stable wildtype's lettuce‐like form (Føyn , Løvlie ).…”