Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: THE PLANT CHROMOSOME - A 1994 VIEW
THE PLANT CHROMOSOME - A 1994 VIEW
Richard Flavell, John Innes Institute, Norwich Research Park,
Colney Norwich, UK RG12 6EY.
A plant chromosome is a product of evolution. To interpret
its structure we need to understand how the myriad of component
sequences and higher order structures have evolved under the
forces of mutation, cellular processes and natural selection.
Plant chromosomes contain sequences that evolve rapidly, often
highly repeated, and evolutionarily conserved sequences including
the genes. Many of the molecular mechanisms that drive rapid
evolution of repeats, especially transposons are known. These
are responsible for the major differences in chromosome
architecture within and between species. We presume natural
selection plays a major role in conserving gene structure. From
comparative genome mapping we are finding extensive synteny for
the genes between distantly related species. Does this reflect
common evolutionary origins or have selective forces preserved
gene order? This synteny will prove to be of enormous value in
the identification and isolation of genes, just as the
conservation of gene sequences is proving to be a major aid for
identification of gene function. Larger chromosomal structures
such as telomeres and centromeres are becoming better defined but
we have much to learn about how a chromosome is organized within
a nucleus and how it is programmed through a cell cycle and
meiosis. The coming years of research will produce a vast amount
of data revealing sequence evolution and function and there will
then be the more complex challenge to relate DNA sequence to
chromosome architecture and behaviour through the cycles of
different cell types. These themes will be discussed with the
aid of specific examples.
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