Revertants of
unc-15(
e73)I, a paralyzed mutant with an altered muscle paramyosin, include six dominant and two recessive intragenic
unc-15 revertants, two new alleles of the previously identified suppressor gene,
sup-3 V, and a new suppressor designated
sup-19(
m210)V. The recessive intragenic
unc-15 revertants exhibit novel alterations in paramyosin paracrystal structure and distribution, and these alterations are modified by interaction with
unc-82(
e1220)IV, another mutation that affects paramyosin. A strain containing both
unc-15 and a mutation in
sup-3 V that restores movement was mutagenized, and paralyzed mutants resembling
unc-15 were isolated. Twenty mutations that interfere with suppression were divided into three classes (nonmuscle,
sus-1, and mutations within
sup-3) based on phenotype, genetic map position and dominance. The nonmuscle mutations include dumpy and uncoordinated types that have no obvious direct effect on muscle organization. Two recessive mutations define a new gene,
sus-1 III. These mutations modify the
unc-15(
e73) phenotype to produce a severely paralyzed, dystrophic double mutant that is not suppressed by
sup-3. Five semidominant, intragenic
sup-3 antisuppressor mutations, one of which occurred spontaneously, restore the wild-type
sup-3 phenotype of nonsuppression. However, reversion of these mutants generated no new suppressor alleles of
sup-3, suggesting that the
sup-3 antisuppressor alleles are not wild type but