Physiology and Molecular Biology of Stress ... - KHAM PHA MOI

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A.K. Tyagi, S. Vij and N. Saini
and glass slides. Microarrays are currently used for studying gene expression. The
change in gene expression is measured by labeling the control and experimental transcript
population with different fluorescent tags and then measuring the intensity and
ratio of fluorescent signals bound to DNA microarray. This technology makes possible
the rapid and comprehensive assessment of transcriptional activity during stress response
and provides new insights into complex signaling networks governing these
stress responses and helps identification of associated new genes. The plant microarray
technology has been extensively reviewed recently (Baldwin et al., 1999; Schaffer et al.,
2000; Aharoni and Vorst, 2002; Donson et al., 2002; Zhu, 2003b).
2.3.1. cDNA Microarray
The cDNA microarray is fabricated by robotically spotting PCR products resulting from
direct amplification of genomic DNA by using EST-based or gene-specific primers on a
glass slide (Jiao et al., 2003). A number of cDNA microarrays have been developed in
plants, e.g. Arabidopsis, rice, maize, strawberry, petunia, ice plants and lima bean. Schena
et al. (1995) first used the cDNA microarray to study the differential expression of 45
genes in roots and shoots in Arabidopsis. This high-throughput technology has been
successfully used to analyze the regulation of genes at different stages of development
(Lemieux et al., 1998; Kehoe et al., 1999) and in response to both abiotic and biotic
stresses (Table 1). In an experiment to study salt stress, yeast transcripts analyzed
using microarray showed that about 300 transcripts (~5% of all open reading frames)
have at least two-fold increase in abundance and about 200 genes were down-regulated
to a similar extent (Cushman and Bohnert, 2000). This study is expected to provide
identification of genes and functional information of cellular tolerance mechanisms that
are evolutionarily conserved. Seki et al. (2002b) prepared a 7,000 full length cDNA
microarray in Arabidopsis to identify genes related to drought, cold, or salinity and to
examine the differences and cross-talk between their signaling cascades. In total, 277
drought-inducible, 53 cold-inducible and 194 salinity-inducible genes were identified.
Only 22 genes were identified as drought-, cold- and salinity-inducible genes, while
70% of salinity-inducible genes were also induced by drought stress, which indicated
a strong correlation between drought and salinity stress response. In maize, the early
post-pollination phase development is particularly sensitive to water deficit (Yu and
Setter, 2003). Using cDNA microarray, it was found that in placenta, the major class of
genes which was up-regulated included stress tolerant proteins like heat shock proteins,
chaperonins, and major intrinsic proteins.
Maleck et al. (2000) have applied microarray technology using Arabidopsis
microarray containing 10,000 expressed sequence tags (~7000 genes), representing 25-
30% of total Arabidopsis genes, to analyze transcriptional programming during the
systemic acquired resistance (SAR) under 14 different chemical and biological conditions
related to SAR. The expression of 413 ESTs was differrent during 14 SAR experiments.
In another experiment, transcriptional changes of 2,375 genes have been ana-