Author
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Muhitch, Michael |
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Submitted to: Aflatoxin Workshop
Publication Type: Abstract Only Publication Acceptance Date: 10/26/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: The maternal tissues that surround the developing sporophyte act as the first line of defense against fungal diseases of the seed. In maize, however, Fusarium verticilliodes is even present in the pedicel tissues of asymptomatic kernels. In order to increase the resistance of maize kernels to infection by Fusarium verticilliodes and other cob-rotting fungi, a cassette is being developed to direct disease resistance gene expression within the pedicel and other maternal tissues that are associated with the developing seed. Toward this goal the gene encoding the cytoplasmic isozyme of glutamine synthetase that is strongly expressed in the pedicel of the developing maize kernel has been cloned. This gene, GS1-2, contains a relatively small 5' upstream (promoter) region of approximately 660 bp. Sequence analysis of the promoter reveals putative motifs corresponding to cis regulatory elements involved in maternal expression of anthocyanin genes and also to elements involved in the regulation nitrogen metabolism gene expression. A deletion series of the 5' upstream region of maize GS1-2 from -664 (relative to the putative transcriptional start site) to -72 were fused to the reporter gene GUS and stably expressed in maize plants. Histochemical analysis of the expression of the -664 full length construct revealed GUS to be strongly expressed in the pedicel, the subtending glumes and in the pericarp, but not in the embryo or the endosperm. When the promoter was deleted to -394 by or shorter, GUS activity was noted in additional kernel and vegetative tissues. The GS1-2 promoter will now be used to test whether expressing antifungal or mycotoxin-metabolizing enzymes within the kernel's maternal tissues does in fact lead to reduced fungal infection. |
