Compositional and transcriptional analyses of reduced zein kernels derived from the opaque2 mutation and RNAi suppression.
Corn protein is largely made up of a group of nutritionally limited storage proteins known as zein. The reduction of zein can be achieved by a transcriptional mutation, opaque2 (o2), or a transgene targeting zein through RNA interference (RNAi). Zein reduction results in an increase of more nutritionally balanced non-zein proteins, and therefore enhance the overall quality of corn protein. In this study, the composition of mature kernels and the transcriptional profile of developing kernels of these two types of zein reduced kernels were compared. Both zein reduced kernels contained higher levels of lysine and tryptophan and free amino acids were 10-20-folds more abundant than the wild-type counterpart. We also found that free lysine contributed partially to the increased lysine in o2 kernels while protein-bound lysine was mainly responsible for the increased lysine in transgenic zein reduction (TZR) kernels. Although they had relatively similar gene expression patterns in developing endosperm, o2 kernels had greater transcriptional changes than TZR kernels in general. A number of transcripts that were specifically down-regulated in o2 were identified. Many promoter sequences of these transcripts contain putative O2 binding motifs, suggesting that their expression is directly regulated by O2.
Frizzi
Alessandra
A
Calgene Campus, Monsanto Company, 1920 Fifth Street, Davis, CA 95616, USA.
Caldo
Rico A
RA
Morrell
James A
JA
Wang
Meng
M
Lutfiyya
Linda L
LL
Brown
Wayne E
WE
Malvar
Thomas M
TM
Huang
Shihshieh
S
D000596:Amino Acids / Q000032:analysis; D015152:Blotting, Northern; D004268:DNA-Binding Proteins / Q000235:genetics*; D056625:Endosperm / Q000235:genetics* / Q000648:ultrastructure; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D009154:Mutation / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D015854:Up-Regulation / Q000235:genetics; D003313:Zea mays / Q000235:genetics* / Q000648:ultrastructure; D015028:Zein / Q000235:genetics* / Q000378:metabolism
D000596:Amino Acids; D004268:DNA-Binding Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C067402:opaque-2 protein, Zea mays; D015028:Zein
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