RFLP MAPPING OF THE MAIZE DZR1 LOCUS, WHICH REGULATES METHIONINE-RICH10-KDA ZEIN ACCUMULATION

The dzr1 locus in maize posttranscriptionally regulates the accumulati on of methionine-rich 10 kDa zein in the endosperm. An allele of this locus present in the inbred line BSSS53, dzr1 + BSSS53, conditions sev eral-fold higher accumulation of the 10 kDa zein in comparison with st andard inbred lines, leading to enrichment of methionine content in BS SS53 by 30%. In a population segregating for high and low 10 kDa zein, dzr1 + BSSS53 was found tightly to cosegregate with a 22 kDa zein gen e cluster, belonging to the Z1C subfamily of alpha-zeins that is locat ed on chromosome 4S. One member of this gene cluster, azs22/6, was est imated to be located less than 0.4 cM from dzr1 + BSSS53, while three other 22 kDa zein genes mapped 3.4 cM away. Restriction fragment lengt h polymorphism (RFLP) mapping of dzr1 was conducted using additional m aize DNA markers and orthologous rice DNA markers. One maize marker, p hp20725, was identified that mapped 1.1 cM from dzr1, proximal to the centromere. Another marker derived from rice, rz329, mapped 6.6 cM dis tal to dzr1. Pulsed-field gel electrophoresis (PFGE) of the 22 kDa zei n cluster showed that probably all copies of the 22 kDa zein genes are present within a 200 kb SalI fragment. The recombination frequency wi thin this cluster was estimated to be 20-fold higher than that predict ed for the maize genome.