Preparing For Climate Change: Analyzing Genome Of Heat And Drought Resistant Cereal Plant
February 7, 2009 — The global climate is changing, and this change is already impacting food supply and security. People living in regions already affected by aridity need plants that can thrive / grow under dry conditions.
One example is sorghum: Also known as milo, durra, or broomcorn, sorghum is a grass species that can grow up to five meters in height and is extremely resistant to aridity and hot conditions. The grass, which originates from Africa, can thrive under conditions and locations where other cereal plants cannot survive due to lack of water. In arid-warm and moderate regions of the Americas, Asia and Europe it is mainly utilized for food and fodder and is also gaining in significance as a basis for bio-fuel. The plant also provides fibers as well as combustible material for heating and cooking.
As part of an international consortium of scientists, researchers at Helmholtz Zentrum München are analyzing the genes of sorghum, the first plant of African origin whose genome has been sequenced.
Dr. Klaus Mayer of the Institute of Bioinformatics and Systems Biology of the Helmholtz Zentrum München described the scientists’ research goal: ”We want to elucidate the functional and structural genomics of sorghum.“ He went on to explain: ”That is the prerequisite for making this important grain even more productive through targeted breeding strategies. As German Research Center for Environmental Health, sustaining the food supply is one of our most important research topics. That is why we are trying to learn something about the molecular basis of the plant’s pronounced drought tolerance in order to apply this knowledge to other crop plants in our latitude zone as well. “The first results of the study have been published in the current issue of Nature.
What makes sorghum interesting as a model system is that it is more closely related to the predominant grains of tropical origin, for example maize, than it is to rice. Moreover, sorghum, unlike many other crop plants, has not undergone genome enlargement in the past millions of years. Its rather small genome – about one-fourth as large as the human genome – is a good starting point for investigating the more complex genomes of important crop plants such as maize or sugarcane, especially since sorghum - like these two plants –is a ”C4 plant“.
Due to biochemical and morphological specialization, such plants use a special kind of photosynthesis (in which first a molecule with four carbon atoms is formed, thus the name). They can assimilate carbon at higher temperatures and more efficiently than ”C3 plants“ and are especially suitable for the production of biomass for energy. Sorghum is the first cereal plant with C4 photosynthesis whose genome has been completely sequenced. The analysis of its functional genomics provides new insights into the molecular differences between C3 and C4 plants.
Furthermore, the comparison with the C3 plant rice - likewise completely sequenced – gives us information about how these cereals became more divergent in the course of evolution.The data of the Munich scientists also allow a comparative analysis of sorghum, rice and maize. This analysis yields information about the evolution of the genome size, distribution and amplification of genes or recombination processes.
Last but not least, the researchers have validated a method in their study - whole genome shotgun sequencing – which is an especially fast and inexpensive method of sequencing complete chromosomes and genomes. In this method, the DNA is copied multiple times and then shredded into many small fragments by squeezing the DNA through a pressurized syringe. Finally the fragments are sequenced from both ends ans subsequentially the millions of small DNA fragments are assembled by elaborate computational methods into complete chromosomes.
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