The Characterization Of Plant Stress-Related GENES

Various abiotic stresses such as, drought, salinity, extreme temperature, wound and so on, could strongly affect the growth and development of plants. The investigation on the molecular mechanism of stress-related genes and stress signaling is not only important but also valuable for future application. Abscisic acid (ABA) plays crucial roles in plants to adapt to harsh environmental stresses. Thus, the study on ABA signaling is very important for us to understand how plants could endure the abiotic stress. High salinity can reduce carbon fixation in plants and decrease crop yield directly. Na+/K+transport plays a key role of salt tolerance in plants. HKT family members are able to transport Na+and K+selectively. Some of HKT transporters can mediate the salt tolerance in plants. We characterized the stress-related genes from two different views that can be shown in two parts in this dissertation.1) The functional analyses on PROG1gene that may be involved in ABA-mediated guard cell movement through ROS in Arabidopsis.2) The comparative analyses on differential Na+and K+transport selectivities of rice OsHKT2;l and OsHKT2;1transporters in plant cells.The results of this study are shown as follows:1. The functional analyses on PROG1gene in Arabidopsis1-1. Overexpressing PROG1gene can enhance ABA sensitivity in ABA-induced stomatal closure. With comparison to wild type Col, the overexpression of PROG1-OE transgenic lines, PROG1-OE2and PROG1-OE14, both show hypersensitive phenotypes in ABA-responsiveness. However, the loss-of-function mutant alleles, progl-1and progl-2, are sensitive to ABA which is similar to Col.1-2. In ABA treatment, PROG1-OE lines can produce higher level of ROS (H2O2) in guard cells compared to wild type Col, which leads to ABA hypersensitive phenotype of PROG1-OE lines.1-3. Overexpression of the PROG1gene can improves the drought tolerance by enhancing antioxidase activity when Arabidopsis plants overaccumulated excess H2O2.1-4. Overexpression of PROG1can downregulate ABI2gene expression and upregulate expression levels of some other ABA responsive genes.1-5. PROG1is expressed mainly in guard cells of various tissues, such as the leaf, stem, flower and silique. In addition, PROG1is expressed in the root tip and meristem.1-6. The PROG1-YFP fusion protein shows the cytosolic localization, i.e., it is localized at the endoplasmic reticulum.1-7. Overexpression of PROG1gene doesn’t affect guard cells development.1-8. The recombinant protein of PROG1shows protease enzyme activity in vitro.1-9. PROG1may interact with TRX3(thioredoxin h-type3).2. The comparative analyses on differential Na+and K+transport selectivities of rice OsHKT2;1and OsHKT2;1transporters in plant cells.Although OsHKT2;1and OsHKT2;2, two highly homologous HKT transporters, share93%identical cDNA sequence and91%identical amino acid sequence, they exhibit differential Na+/K+transport selectivities when expressed in tobacco B Y2cells.2-1. In plant cells, OsHKT2;1mediated Na+uptake, but little Rb+(K+)uptake. In contrast, OsHKT2;2mediated Na+-K+co-transport such that extracellular K+stimulated OsHKT2;2-mediated Na+influx and vice versa.2-2. At millimolar Na+concentrations, OsHKT2;2mediated Na+influx into plant cells without adding extracellular K+.2-3. The presence of external K+and Ca2+downregulate OsHKT2;1-mediated Na+influx.