A KALILO-LIKE LINEAR PLASMID IN LOUISIANA FIELD ISOLATES OF THE PSEUDOHOMOTHALLIC FUNGUS NEUROSPORA-TETRASPERMA

Two Louisiana strains of Neurospora tetrasperma contain a linear plasm id (LA-kalDNA) with a restriction map identical to the Hawaiian Neuros pora intermedia senescence plasmid, kalDNA, but with termini 100 nucle otide pairs shorter. One of these strains also bore a circular plasmid similar to the Hawaiian circular plasmid Hanalei-2. One species proba bly acquired both plasmids from the other by horizontal transfer, at a time sufficiently distant for sequence divergence to take place. Many LA-kalDNA-bearing derivative strains senesced, but this plas mid does not guarantee senescence. Furthermore, LA-kalDNA does not insert into mtDNA. One senescent strain showed no LA-kalDNA. The plasmids are eff ectively transmitted via the pseudohomothallic sexual cycle. Single ma ting-type derivatives transmit plasmids maternally.