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Andrew H. Paterson talks with
ScienceWatch.com and answers a few questions about
this month's New Hot Paper in the field of Plant & Animal
Science. The author has also sent along an image of his
work.
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Article Title: The Sorghum bicolor genome and the
diversification of grasses
Authors: Paterson, AH, et al.
Journal: NATURE, Volume: 457, Issue: 7229, Page: 551-556, Year:
JAN 29 2009
* Univ Georgia, Plant Genome Mapping Lab, Athens, GA 30602
USA.
* Univ Georgia, Plant Genome Mapping Lab, Athens, GA 30602
USA.
* Rutgers State Univ, Waksman Inst, Piscataway, NJ 08854
USA.
(addresses have been
truncated.)
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Why do you think your paper is highly
cited?
As the second fully sequenced cereal genome (rice being the first), sorghum
permitted us to compare these divergent lineages in the flowering plant
group (grasses) that provides humanity with most of its food and feed, and
a growing share of its fiber and fuel.
Sorghum also added new dimensions to our ability to compare monocots
(including the cereals) to eudicots such as the other flowering plant
genomes sequenced to date. The importance of sorghum as a botanical model
for food/feed/fodder/biomass production makes this work important to the
transition to a more bio-based economy.
Better understanding of its drought tolerance may help in adapting to a
future in which agriculture has access to a smaller portion of the world's
water supply. Unique physiological mechanisms (i.e., traits) underpinning
its high nitrogen use efficiency (NUE) may benefit other crops, and reduce
nitrate runoff into the world's waterways.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
We described the largest and most complex plant genome that had been
sequenced using the whole-genome shotgun approach, at that time.
In addition to the value of sorghum itself for comparative biology
(detailed above), this work illustrates the high level of sequence
contiguity and accuracy that may be achieved by using the whole-genome
shotgun sequencing approach to clothe a backbone of detailed genetic and
physical maps.
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Sorghum
stands tall.
[+]View
larger image &
details...
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Our work suggests that hundreds of additional plant genomes (including most
of the crops that sustain humanity) may be amenable to this sequencing
approach, despite high levels of gene duplication and repetitive DNA.
A surprise regarding the organization of this relatively large genome
appears to be true of many additional plant genomes. Remarkably, about 985
of the recombinations in this genome and the vast majority of gene-like
sequences are contained in about one-third of the total chromosomal DNA.
This suggests various strategies to more affordably generate very
informative partial sequences of complex genomes of many other grasses and
other plant species, and should help us to reduce our reliance on a very
small number of crops as sources of our food, feed, fuel, and fiber.
Would you summarize the significance of your paper
in layman's terms?
Initial analysis of the sorghum genome sequence provides insights into the
"parts list" of plants that are well-adapted to converting sunlight and
carbon dioxide into usable products (grain and biomass) at high
temperatures and with a minimum of water.
This knowledge will help to accelerate improvement of the relatively small
and simple genome of sorghum to meet human needs for food and
biomass/biofuel, and also will accelerate improvement of its close
relatives with much larger and more complex genomes, such as sugarcane and
"giant Chinese silver grass" (Miscanthus), which reaches 12 feet
in height and has silvery plumes that are well-separated above the
cornstalk-like foliage in late summer.
How did you become involved in this research, and
were there any problems along the way?
When I started down this road in 1992, plant genomics was in its infancy.
Funding for plant genomics research was modest, and the importance of
sorghum was appreciated by only a small community of scientists and
stakeholders.
Improved genomics technology and heightened awareness of what genomics
could offer, the resurgence of interest in biofuels, increased awareness of
the need to produce crops with less water, and invigorated international
efforts to enhance the quality and stability of the food supply in Africa
(where sorghum is native, and a staple) all helped to bring the sequence to
fruition.
Where do you see your research leading in the
future?
The reference genome of sorghum opens many new doors to better utilize the
intrinsic genetic potential of plants to meet human needs. We are working
to learn about functions of specific genes that differentiate sorghum from
other botanical models and/or major crops.
Also, the sequence reveals that different regions of the genome of sorghum
and other grasses have evolved by very different mechanisms and at very
different rates. We would like to learn the causes of this phenomenon and
the reasons for it.
Do you foresee any social or political
implications for your research?
Sorghum is well-suited to several niches in the global agro-ecosystem that
are likely to be of growing importance. Already, it is an essential staple
in much of Africa, especially in the Sahel region where episodic drought is
frequent and challenges to development are great.
Improved yield stability (especially drought tolerance and resistance to
insect pests and hemi-parasitic weeds from the genus Striga) and
nutritional quality of food/feed produced from sorghum grain is one
important dimension needed in an integrated effort to better meet the basic
needs of some of the world's poorest people in some of the world's most
difficult agricultural environments.
The drought tolerance of sorghum makes it of growing interest well outside
its native region in Africa. Presently, agriculture enjoys access to a
large share of the world's water supplies, but population growth and
climatic changes suggest that many parts of the world will face a "water
crisis" in the next few decades.
Expanded production of sorghum itself may contribute to an agricultural
system that can better sustain humanity while using less water.
Furthermore, identifying the genetic determinants of sorghum's intrinsic
drought tolerance may contribute to the improvement of other crop plants
(such as maize) to be more drought tolerant and/or water-use efficient.
Increased production of sorghum and its close relatives may reduce
dependence on fossil fuels. Sorghum is the #2 source of seed-based biofuel
(after maize) in the USA, and it shows much promise as a source of
"next-generation" biofuel from lignocellulosic tissues.
Perennial forms of sorghum offer the means to breed genotypes that can be
produced on marginal soils that are not well-suited to food production,
with a minimum of cultivation to mitigate erosion.
Rapid progress envisioned in learning about the functions of sorghum genes
is expected to translate well to its close relatives, sugarcane (arguably
the leading biofuel crop worldwide), and Miscanthus (a singularly
promising biofuel crop for temperate regions).
Recent studies have also shown that sorghum appears to be unique among
cultivated cereals in having the ability to protect its nitrogen supply
from nitrification by soil microbes. This "biological nitrification
inhibition" capacity of sorghum has tremendous potential to improve NUE of
crop production and reduce nitrate pollution of waterways associated with
intensive crop production.
Andrew Paterson, Ph.D.
Distinguished Research Professor
and Director
Plant Genome Mapping Laboratory
University of Georgia
Athens, GA, USA
Web |
Web
Figure 1:
Figure 1:
Sorghum stands tall. Comparison of the completed genome sequences of rice
(foreground) and sorghum (background) provides insight into the ~70-million
year evolutionary history of Poaceae grasses that provide much of
our food, animal feed, and fodder, as well as a growing share of our fuel.
These two grasses, together with the more recently sequenced
Brachypodium distachyon, are attractive models for determining the
functions of genes that are important to the productivity and quality of a
wide range of seed/grain, turf, forage, and biomass crops, as well as the
spread and persistence of many weedy/invasive grasses. Ongoing studies are
expected to provide insights into productivity under favorable conditions,
drought and disease resistance under unfavorable conditions, reproductive
biology, nutritional value, compositional properties related to biofuel
uses, and many other dimensions of grass biology. Photo credit Dr. C. T.
Hash, ICRISAT.
KEYWORDS: MAIZE GENOME; RICE GENOME; WIDE ANALYSIS; CELL-WALLS; EVOLUTION;
SEQUENCE; GENES; IDENTIFICATION; RECOMBINATION; DUPLICATION.
