New Insights into Desiccation-Associated Gene Regulation by Lilium longiflorum ASR during Pollen Maturation and in Transgenic Arabidopsis - International Review of Cell and Molecular Biology - page 51

organic molecules that accumulate in cells in response to desiccation and
other abiotic stresses. The most common osmoprotectants are betaine, pro-
line and soluble sugars, which can help to maintain the conformation of
proteins or act as chaperones to help in the refolding of the proteins that
are prone to aggregation or unfolding during cellular dehydration ( Pareek
et al., 2010 ). Recent reports have shown that overexpression of transcrip-
tion factor genes improves stress tolerance ( Gao et al., 2011 ; Xu et al., 2011 ).
4. TRANSGENIC 35S::LLA23 PLANTS
4.1. Transgenic 35S::LLA23 Plants Exhibit Desiccation-
Resistant Phenotype
The coding region of LLA23 fused to the cauliflower mosaic virus 35S
promoter was used to transform Arabidopsis (ecotype Columbia [Col])
plants and T3 kanamycin-resistant homozygous lines were generated. The
35S::LLA23 plants are less sensitive to ABA and more dehydration-tol-
erant than wild-type plants. As shown in Fig. 2.3 A and B, the growth and
development of LLA23-overexpressing plants in soil in the growth cham-
ber without stress appeared normal. When the soil was allowed to dry by
withholding water, 48% of both independent 35S::LLA23 lines and 84%
of the wild-type plants became wilted 12 days after the withdrawal of water
(Fig. 2 . 3 C). The two 35S::LLA23 lines that remained upstanding did not
begin to wilt until 16 days after the withdrawal of water (data not shown).
When the wilted plants were rewatered afterward, only 5% of the wilted
wild-type plants recovered, whereas 50% of both wilted 35S::LLA23 lines
survived to maturity (Fig. 2 . 3 D). Corroborating data were obtained when
the rate of water loss from detached leaves of wild-type and LLA23-over-
expressing plants was compared. The leaves tested were of similar size and
age. Leaves of transgenic plants overexpressing the LLA23 protein had lower
rates of water loss than that of wild-type plants (Fig. 2 . 3 E). Microscopic
of each genotype and three replicates each). Wilted plants were then rewatered (day
13), and the number of recovered plants (fully regained turgor and resumed growth)
was scored after an additional 4 days (day 16) and represented as the percentage of
the wilted plants. Open bar, wild type; closed bars, 35S::LLA23C ; gray bars, 35S::LLA23E .
Error bars represent SD. E: Water loss from the leaves of wild-type and 35S::LLA23 plants.
Detached leaves of wild-type or LLA23-overexpressing plants were assayed for water
loss. F: Micrographs showing the stomatal closure regulation of 35S::LLA23E and wild-
type plants under drought stresses for 12 and 16 days, respectively. All images were
taken at the same scale (bar = 30 mm). (From Yang et al. (2005) with permission from
American Society of Plant Physiologists).