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United States Department of Agriculture

Agricultural Research Service


item Khavkin, Emil
item Coe Jr, Edward

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: This study asks whether genes significant to crop productivity have random locations in the chromosomes. In the 10 chromosomes of maize, genes that affect growth, development, and stress response are in clusters on the chromosome maps, i.e., nonrandomly distributed. Evidence for clustering was derived through summarization and analysis of locations of these classes of genes, with the map locations at which inheritance of quantitatively measured traits has been demonstrated. The value of this information is that it suggests a further need to develop focused and incisive breeding strategies for crop improvement. Because significant genes are clustered, the following impacts are evident: 1) advancements are needed in methods for recombining blocks of genes and for increasing map resolution; and 2) advancements require more detailed definition of cell signalling and coordination of functions within plant cells.

Technical Abstract: In maize, genes for growth, development, and stress response associate into functional clusters, 10 to 30 cM long, distributed nonrandomly along all 10 chromosomes. These clusters comprise the loci for environmental and hormonal perception, the loci for the growth machinery (e.g., genes for the enzymes of hormone synthesis, mutations disturbing sporophyte and gametophyte development, or genes for programmed cell death) and the maste genes (e.g., transcription factors) presiding over spatial and temporal transitions in cell growth and differentiation. Taking into consideration mapping accuracy, these genes generally coincide also with the location of homeobox genes as determined with cDNA probes. Upon parallel analysis of over 800 quantitative trait loci (QTLs) for plant architecture, growth, and development in vivo and in vitro, grain yield as the integer of growth, and abscisic acid accumulation and effects, the majority also map within these clusters. Concomitantly, several physiologically different quantitative traits governing plant development and yield are often mapped by the same molecular probe. The clusters are redundant, apparently due to duplication events in the course of maize evolution. We presume that these clusters are the functional units of genes expressed in concert to contribute toward plant development and apparently to some of the plant responses to abiotic stress. The major QTLs for plant height, earliness, and grain yield are the visible manifestations of these developmental clusters. The physiological advantage of close association of functionally related genes in clusters may rely on compartmentation of signal molecules, which helps cooperatively recruit the transcription factors into multicomponent regulatory modules of high specificity.

Last Modified: 08/21/2017
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