Revertants and recombinants in bz2 alleles with Mu insertions

--Virginia Walbot

Heterozygotes were constructed between different mutable alleles of bz2 containing Mu insertions:

bz2-Mu1/bz2-mu2 both Mu1 insertions, approx. 800bp apart
bz2-Mu1/bz2-mu3 both Mu1 insertions, approx. 400bp apart
bz2-Mu1/bz2-Mu9 Mu1 and Mu9 insertions, approx. 300bp apart
bz2-mu2/bz2-mu3 both Mu1 insertions, approx. 400bp apart
bz2-mu2/bz2-Mu9 Mu1 and Mu9 insertions, approx. 500bp apart

In a population of 194,600 kernels from active lines 3 purple kernels were found (1.5 x 10-5) representing revertants, recombinants, and/or gene conversion events. Similar lines with an inactive Mutator system were screened yielding 2 purple kernels among 377,900 progeny (5.3 x 10-6) from recombination and/or gene conversion events. From these data it appears that an active Mutator system does little to enhance intragenic recombination and/or gene conversion events. Dooner, HK and colleagues have demonstrated a similar lack of effect of Mu1 insertions (Dooner and Ralston, Maydica 34:333, 1990). They concluded that Mu1 insertions act in a manner similar to point mutations, in contrast to Ds insertions that appear to favor the recovery of conversion events compared to intragenic recombinants (Ralston et al., Genetics 119:185, 1988; Dooner, Genetics 113:135, 1986).

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