Genetic control of gene expression: independent location of flt(3) and its interactions with the mutable v locus in Nicotiana.

New information has resulted from studies comparing the genetic behavior of two experimental cultures, termed variegated-3 and variegated-1, which arose earlier following an interspecific cross. Phenotypic expression in the plant material involves distinctive variegation patterns of anthocyanin distribution in floral tissues.-The data are consistent with the hypothesis that the genetic constitution of variegated-3 includes a unique and independently segregating regulator component, Flt(3), in addition to the v locus element held in common with variegated-1. Flt(3) has not been generated anew within the variegated-1 genotypes among more than 10,000 observed progeny. Presence of Flt(3) modifies the timing of somatic sectoring events, and is correlated with the capability to produce, in germ cell lines of phenotypically flecked plants, frequent changes at the v locus to a stable, non-variegating, dominant allelic form, V.-The latter process is of special interest because progeny tests of mutant individuals, containing newly-arisen V alleles, fail to reveal continued presence of Flt(3). Thus the mechanism generating V from v appears to be correlated invariably with loss or inactivation of the controllingelement inducing this class of mutations, which is located initially on a different chromosome from that bearing v.