75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

239 Accumulation of Reactive Oxygen Species in Ovules Reduces Plant Fertility
Yahya Mohammed, D. Head, Bernard Hauser
University of Florida, Gainesville, FL 32611-8526
In response to environmental stress in many plants, ovules and seeds degenerate during their development, dramatically
reducing the number of seeds and fruits produced. In Arabidopsis, salt stress induces programmed cell death (PCD) in
ovules, but not in the surrounding carpel walls and the transmitting tract. Transcript levels from healthy ovules were
compared with those found in ovules when they commit to undergo PCD. The expression of transcripts encoding some
enzymes that detoxify reactive oxygen species (ROS) decrease once ovules committed to abort. These changes in gene
expression coincided with the accumulation of ROS in female gametophytes. Because ROS activate genetic programs
that trigger PCD, the rates of ovule abortion and fertility were examined in ROS scavenging mutants. Of the loci that
exhibited significant changes in gene expression following salt stress, two peroxidase mutants and a superoxide dismutase
(SOD) mutant were evaluated. When compared to wild-type plants, the sod mutant accumulated ROS in healthy ovules.
Qualitative assays reveal that both peroxidase mutants have elevated ROS levels in healthy and stressed ovules. In these
peroxidase mutants, increased accumulation of ROS led to moderate, but significant, decreases in plant fertility. This
result indicates that ROS accumulation is sufficient to reduce fertility. Interestingly, reduced ROS scavenging attenuated
fertility, but did not eliminate it. This indicates that multiple control points adjust reproduction to match environmental
conditions.
240 An Arabidopsis Cyclin –Like Protein, CLP, Is Involved in Drought Stress Response and Plant
Development
Yin Hua Jin 1 , Jing Bo Jin 1 , Dae-Jin Yun 2 , Paul Hasegawa 1 , Ray Bressan 1
1
Purdue University, 2 Gyeongsang National University
The Arabidopsis genome contains 50 putative cyclin proteins, But only very few functional studies of plant cyclins
have been reported to date. Here we show that mutation of cyclin-like protein, CLP, cause drought sensitive phenotype
and abnormal plant organ development. The clp mutant plant was originally obtained from screening of Arabidopsis
T-DNA insertion mutant pools in the C24 background, which carry the firefly luciferase reporter gene driven by RD29A
promoter (RD29A::LUC). The clp mutant plant showed extremely high constitutive bio-luminescence level, without any
treatment. Genetic analysis of F1 and F2 backcrossed plants revealed that the mutation is dominant and mutant phenotype
is caused by single mutation. The clp plant exhibit extreme drought sensitive phenotype and the phenotype could not be
rescued by exogenous ABA treatment. Moreover, the clp plant shows greater water loss compare to wild-type plant. The
clp seedling development is insensitive to ABA . The clp plants also exhibit wider rosette leaves and increased numbers
of trichomes on the rosette leaves and stems compared to C24 wild type plants. The clp plants also have abnormal petal
and stamen numbers in the terminal flowers. These results suggest that the CLP plays important roles in ABA response
and maintenance of plant organ morphology.