DOSAGE REGULATION OF ZEA-MAYS HOMEOBOX (ZMHOX) GENES AND THEIR RELATIONSHIP WITH THE DOSAGE-SENSITIVE REGULATORY FACTORS OF SHRUNKEN-1 (SH1) IN MAIZE

In gene dosage studies on the expression of the maize Shrunken 1 gene, several dosage-sensitive regulatory factors were identified that modu late Sh 1 mRNA levels in various aneuploids. ZmHox1a and 1b have been shown to interact with the Sh 1 promoter sequences in vitro. The prese nt study was conducted to test whether these molecularly defined regul atory genes are subject to dosage modulation and to determine whether ZmHox1a and 1b are involved with the dosage-sensitive modification of Sh 1 expression. The result was that ZmHox1a and 1b were affected by s everal transacting dosage modifiers and that both genes exhibited a st ructural gene dosage effect but did not modulate Sh 1 mRNA levels. For some chromosomal regions, a correlation was found between the dosage regulation of Sh 1 and that of ZmHox1a, while other effects were not c orrelated. The results suggest that the dosage effects on Sh 1 are not mediated by ZmHox1a or 1b, but interestingly Sh 1 and ZmHox1a share s ome dosage-regulatory effects. (C) 1997 Wiley-Liss, Inc.