Blacksburg, Virginia
September 11, 2007
An international team of
scientists has produced a new type of rice that grows better and
uses water more efficiently than other rice crops. Professor
Andy Pereira at the Virginia
Bioinformatics Institute (VBI) has been working with
colleagues in India, Indonesia, Israel, Italy, Mexico and The
Netherlands to identify, characterize and make use of a gene
known as HARDY that improves key features of this important
grain crop.
The research, which was recently published in the Proceedings of
the National Academy of Sciences, shows that HARDY contributes
to more efficient water use in rice, a primary source of food
for more than half of the world’s population. *
Rice (Oryza sativa) is a water guzzler when compared to other
crops. It typically uses up to three times more water than other
food crops such as maize or wheat and consumes around 30% of the
fresh water used for crops worldwide. In conditions where water
is scarce, it is important to have crops that can efficiently
generate biomass (plant tissue) using limited amounts of water.
HARDY rice shows a significant increase in biomass under both
drought and non-drought conditions. The researchers found that
the biomass of HARDY rice increased by around 50% under
conditions of water deprivation (drought) compared to the
unmodified version of the same type of rice.
Dr. Andy Pereira, Professor at VBI, stated: “This
transdisciplinary research project involved the study of two
plants. First we used a powerful gain-of-function screening
technique to look at a large number of Arabidopsis plants that
might have features favorable to water and drought resistance.
We were able to identify the HARDY mutant due to its
considerable reluctance to be pulled from the soil and its
smaller, darker green leaves. Molecular and physiological
characterization showed that the improved water usage efficiency
was linked to the HARDY gene.”
Dr. Aarati Karaba, who worked on the project as a graduate
student jointly at the University of Agricultural Sciences in
Bangalore, India, and at Plant Research International,
Wageningen, The Netherlands, commented: “The next step was to
introduce the HARDY gene into rice and examine the features
arising from this transformation. In rice, HARDY seems to work
in a slightly different way than Arabidopsis but it still leads
to improved water-use efficiency and higher biomass. Further
studies showed that HARDY significantly enhances the capacity of
rice to photosynthesize while at the same time reducing water
loss from the crop.”
Dr. Andy Pereira, added: “DNA microarray analysis allowed us to
look at gene expression patterns regulated by HARDY. We
specifically focused on genes that have gene ontology (GO)
terms, namely genes that have been assigned by the scientific
community to specific biological processes or functions. Using
this approach we were able to identify clusters of known genes
regulated by HARDY whose levels changed under conditions of
plant water deprivation. We also saw distinct changes of gene
clusters linked to the metabolism of key proteins and
carbohydrates, which probably explains some of the feature
differences we have detected in Arabidopsis and rice.”
The scientists have been able to track down these improvements
in water-use efficiency to a specific type of molecule known as
AP2/ERF-like transcription factor. Transcription factors are
proteins that bind to DNA and control gene expression and the
HARDY gene encodes a protein that belongs to a specific class of
AP2/ERF-like transcription factors. Shital Dixit, Graduate
student at Plant Research International, Wageningen, The
Netherlands, commented: “At this point in time, we do not know
the exact function of this transcription factor although we
suspect that it impacts maturation processes linked to tissue
desiccation. More work remains to be done to elucidate the
precise function of this protein as well as the processes on
which it has a major impact. What is clear is that HARDY rice
offers the exciting prospect of improved water-use efficiency
and drought resistance in rice and perhaps other grain or seed
crops. This should contribute in a sustainable way to
maintaining high crop yields under conditions of limited water
availability.”
* Improvement of water use efficiency in rice by
expression of HARDY an Arabidopsis drought and salt tolerance
gene
Karaba A, Dixit S, Greco R, Aharoni A, Trijatmiko KR,
Marsch-Martinez N, Krishnan A, Nataraja KN, Udayakumar M,
Pereira A (2007)
Proceedings of the National Academy of Sciences, in press. |
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