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Miclaus, M., Wu, Y., Xu, J-H., Dooner, H. K., and Messing, J. The Maize High-lysine Mutant opaque7 is Defective in an acyl-CoA Synthetase-like Protein. Genetics, 10.1534/genetics.111.133918, 2011.

Abstract: Maize (Zea mays) has a large class of seed mutants with opaque or nonvitreous endosperms that could improve the nutritional quality of our food supply.
The phenotype of some of them appears to be linked to the improper formation of
protein bodies (PBs) where zein storage proteins are deposited. Although a
number of genes affecting endosperm vitreousness have been isolated, it has
been difficult to clone opaque7 (o7), mainly because of its low penetrance in
many genetic backgrounds. The o7-reference (o7-ref) mutant arose
spontaneously in a W22 inbred, but is poorly expressed in other lines. We report
here the isolation of o7 with a combination of map-based cloning and transposon
tagging. We first identified an o7 candidate gene by map based cloning. The
putative o7-ref allele has a 12-bp in-frame deletion of codons 350 to 353 in a
528-codon long acyl-CoA synthetase-like gene (ACS). We then confirmed this
candidate gene by generating another mutant allele from a transposon-tagging
experiment using the Activator/Dissociation (Ac/Ds) system in a W22
background. The second allele, isolated from approximately 1 million gametes,
presented a 2-kb Ds insertion that resembles the single Ds component of doubleDs, McClintock’s original Dissociation element, at codon 496 of the ACS gene.
PBs exhibited striking membrane invaginations in the o7-ref allele and a severe
number reduction in the Ds-insertion mutant, respectively. We propose a model
in which the ACS enzyme plays a key role in membrane biogenesis, by taking
part in protein acylation, and that altered PBs render the seed non-vitreous.

Keywords: opaque7; Acyl-CoA; transposon tagging; endosperm; protein bod


Posted by Mihai Miclăuș


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