REVIEW
Transgenic approaches for abiotic stress tolerance in plants:
retrospect and prospects
Pooja Bhatnagar-Mathur Æ V. Vadez Æ
Kiran K. Sharma
Received: 20 August 2007 / Revised: 21 October 2007 / Accepted: 22 October 2007 / Published online: 20 November 2007
Ó Springer-Verlag 2007
Abstract Abiotic stresses including drought are serious
threats to the sustainability of crop yields accounting for
more crop productivity losses than any other factor in
rainfed agriculture. Success in breeding for better adapted
varieties to abiotic stresses depend upon the concerted
efforts by various research domains including plant and
cell physiology, molecular biology, genetics, and breeding.
Use of modern molecular biology tools for elucidating the
control mechanisms of abiotic stress tolerance, and for
engineering stress tolerant crops is based on the expression
of specific stress-related genes. Hence, genetic engineering
for developing stress tolerant plants, based on the intro-
gression of genes that are known to be involved in stress
response and putative tolerance, might prove to be a faster
track towards improving crop varieties. Far beyond the
initial attempts to insert ‘‘single-action’’ genes, engineering
of the regulatory machinery involving transcription factors
has emerged as a new tool now for controlling the
expression of many stress-responsive genes. Nevertheless,
the task of generating transgenic cultivars is not only
limited to the success in the transformation process, but
also proper incorporation of the stress tolerance. Evaluation
of the transgenic plants under stress conditions, and
understanding the physiological effect of the inserted genes
at the whole plant level remain as major challenges to
overcome. This review focuses on the recent progress in
using transgenic technology for the improvement of abiotic
stress tolerance in plants. This includes discussion on the
evaluation of abiotic stress response and the protocols for
testing the transgenic plants for their tolerance under close-
to-field conditions.
Keywords Abiotic stress Á Drought tolerance Á
Genetic engineering Á Transcription factors Á
Transpiration efficiency
Introduction
Abiotic stresses adversely affect growth and productivity
and trigger a series of morphological, physiological, bio-
chemical and molecular changes in plants. Drought,
temperature extremes, and saline soils are the most com-
mon abiotic stresses that plants encounter. Globally,
approximately 22% of the agricultural land is saline (FAO
2004), and areas under drought are already expanding and
this is expected to increase further (Burke et al. 2006).
Often crops are exposed to multiple stresses, and the
manner in which a plant senses and responds to different
environmental factors appears to be overlapping. Gene
expression profiles of either drought- or salt-stressed barley
plants indicated that although, various genes were differ-
entially regulated in response to different stresses, they
possibly induce a similar defense response (Ozturk et al.
2002).
When a plant is subjected to abiotic stress, a number of
genes are turned on, resulting in increased levels of several
metabolites and proteins, some of which may be respon-
sible for conferring a certain degree of protection to these
stresses. A key to progress towards breeding better crops
under stress has been to understand the changes in cellular,
biochemical and molecular machinery that occur in
response to stress. Modern molecular techniques involve
Communicated by P. Kumar.
P. Bhatnagar-Mathur Á V. Vadez Á K. K. Sharma (&)
International Crops Research Institute for the Semi-Arid Tropics
(ICRISAT), Patancheru, Andhra Pradesh 502 324, India
e-mail: k.sharma@cgiar.org
123
Plant Cell Rep (2008) 27:411–424
DOI 10.1007/s00299-007-0474-9