Cold Spring Harbor, New York
September 24, 2008
 Cold
Spring Harbor Laboratory (CSHL) professor David Jackson,
Ph.D., and a team of plant geneticists have identified a gene
essential in controlling development of the maize plant,
commonly known in the United States as corn. The new research
extends the growing biological understanding of how the
different parts of maize arise--important information for a
plant that is the most widely planted crop in the U.S. and a
mainstay of the global food supply.
The researchers found that a gene called sparse inflorescence1,
or spi1, is involved the maize plant's synthesis of the growth
hormone auxin. This chemical messenger is familiar to biology
students, who learn that it is produced by the tip of a growing
shoot. When the hormone is applied to only one side of the
shoot, that side grows faster, causing the tip to bend.
In a much more complex process, auxin also helps to shape
structures such as leaves or the female organs (ears) and male
organs (tassels) of corn. The initial stages of these structures
are called meristems, which consist of versatile,
undifferentiated cells analogous to the stem cells found in
animals. Jackson and colleagues from UC San Diego, including
Andrea Gallavotti who spent one year in Jackson’s lab to perform
some of this work, and at California State University at Long
Beach and Pennsylvania State University, found that meristems
emerge from an interplay between the synthesis of auxin by
various cells and its motion between them. Disrupting either its
production (by causing a mutation in the spi1 gene) or its
motion results in stunted, defective organs.
Eudicots vs. Monocots
Much has been learned in the past about organ development in the
cress plant known as Arabidopsis, which biologists regard as a
“model organism” for plant research, much as the lab mouse has
served as a model for research on mammalian biology. Arabidopsis
is in a plant group called eudicots, however, while maize and
many other food crops belong to a group known as monocots. The
spi1 gene has cousins that affect auxin synthesis and organ
formation in Arabidopsis, but there are important differences.
“In maize, spi1 mutations cause severe developmental effects,
which is not the case in Arabidopsis, which we demonstrated by
deleting, or ‘knocking-out,’ genes similar to spi1,” Jackson
explained. “Our work helped demonstrate that spi1 in maize has
evolved a dominant role in auxin biosynthesis, and is essential
for what we plant scientists call inflorescence development--the
process in seed plants in which a shoot forms that supports the
plant’s flowers,” he added.
“When we looked at the interaction between spi1 and genes of the
plant that regulate auxin transport, we found, interestingly,
that the transport of auxin and biosynthesis work together in a
synergistic manner to regulate how the meristem and lateral
organs of the maize plant develop.”
“sparse inflorescence1 encodes a monocot-specific YUCCA-like
gene required for vegetative and reproductive development in
maize” received advanced online publication in the Proceedings
of the National Academy of Sciences on September 17, 2008. The
complete author list is: Andrea Gallavotti, Solmaz Barazesh,
Simon Malcomber, Darren Hall, David Jackson, Robert Schmidt, and
Paula McSteen. The paper is available at
http://dx.doi.org/10.1073/pnas.0805596105.
Cold Spring Harbor Laboratory (CSHL) is a private,
not-for-profit research and education institution at the
forefront of efforts in molecular biology and genetics to
generate knowledge that will yield better diagnostics and
treatments for cancer, neurological diseases and other major
causes of human suffering. |
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