Translationally controlled tumor protein (TCTP), also termed P23 in human, belongs to a family of calcium-and tubulin-binding proteins, and it is generally regarded as a growth-regulating protein. Recently, Arabidopsis TCTP (AtTCTP) has been reported to function as an important growth regulator in plants. On the other hand, plant TCTP has been suggested to be involved in abiotic stress signaling such as aluminum, salt, and water deficit by a number of microarray or proteomic analyses. In this study, the biological functions of AtTCTP were investigated by using transgenic Arabidopsis plants overexpressing AtTCTP. Interestingly, AtTCTP overexpression enhanced drought tolerance in plants. The expression analysis showed that AtTCTP was expressed in guard cells as well as in actively growing tissues. Physiological studies of the overexpression lines showed increased ABA-and calcium-induced stomatal closure ratios and faster stomatal closing responses to ABA. Furthermore, in vitro protein-protein interaction analysis confirmed the interaction between AtTCTP and microtubules, and microtubule cosedimentation assays revealed that the microtubule binding of AtTCTP increased after calcium treatment. These results demonstrate that the overexpression of AtTCTP confers drought tolerance to plants by rapid ABA-mediated stomatal closure via the interaction with microtubules in which calcium binding enhances the interaction. Collectively, the present results suggest that the plant TCTP has molecular properties similar to animal TCTPs, such as tubulin-and calciumbinding, and that it functions in ABA-mediated stomatal movement, in addition to regulating the growth of plants.

A plant-derived 0.3 kb constitutive promoter was obtained from AtTCTP expression analysis, and successfully applied to the expression of a selectable marker gene for production of transgenic creeping bentgrass plants. The isolation and use of an efficient promoter is essential to develop a vector system for efficient genetic transformation of plants, and constitutive promoters are particularly useful for the expression of selectable marker genes. In this study, we characterized a small size of the constitutive promoter from the expression analysis of Arabidopsis thaliana translationally controlled tumor protein (AtTCTP) gene. Histochemical and fluorometric GUS analyses revealed that a 303 bp upstream region from the start codon of the AtTCTP gene showed strong GUS expression throughout all plant tissues, which is approximately 55 % GUS activity compared with the cauliflower mosaic virus 35S promoter (35Spro). To examine the possible application of this promoter for the development of genetically engineered crops, we introduced pCAMBIA3301 vector harboring the 0.3 kb promoter of AtTCTP (0.3kbpro) that was fused to the herbicide resistance BAR gene (0.3kb pro ::BAR) into creeping bentgrass. Our transformation results demonstrate that transgenic creeping bentgrass plants with herbicide resistance were successfully produced using 0.3kb pro ::BAR as a selectable marker. Northern blot analysis revealed that the transgenic plants with 0.3kb pro ::BAR showed reduced but comparable expression levels of BAR to those with 35S pro ::BAR. Moreover, the transcription activity of the 0.3 kb promoter could be increased by the fusion of an enhancer sequence. These results indicate that the 0.3 kb AtTCTP promoter can be used as a plant-derived constitutive promoter for the expression of selectable marker genes, which facilitates its use as an alternative to the 35S promoter for developing genetically engineered crops.

Phytochrome A (phyA) in higher plants is known to function as a far-red/shade light-sensing photoreceptor in suppressing shade avoidance responses (SARs) to shade stress. In this paper, the Avena PHYA gene was introduced into creeping bentgrass (Agrostis stolonifera L.) and zoysiagrass (Zoysia japonica Steud.) to improve turf quality by suppressing the SARs. In addition to wild-type PHYA, a hyperactive mutant gene (S599A-PHYA), in which a phosphorylation site involved in light-signal attenuation was removed, was also transformed into the turfgrasses. Phenotypic traits of the transgenic plants were compared to assess the suppression of SARs under a simulated shade condition and outdoor field conditions after three growth seasons. Under the shade condition, the S599A-PhyA transgenic creeping bentgrass plants showed shade avoidance-suppressing phenotypes with a 45 % shorter leaf lengths, 24 % shorter internode lengths, and twofold increases in chlorophyll concentrations when compared with control plants. Transgenic zoysiagrass plants overexpressing S599A-PHYA also showed shade-tolerant phenotypes under the shade condition with reductions in leaf length (15 %), internode length (30 %), leaf length/width ratio (19 %) and leaf area (22 %), as well as increases in chlorophyll contents (19 %) and runner lengths (30 %) compared to control plants. The phenotypes of transgenic zoysiagrass were also investigated in dense field habitats, and the transgenic turfgrass exhibited shade-tolerant phenotypes similar to those observed under laboratory shade conditions. Therefore, the present study suggests that the hyperactive phyA is effective for the development of shade-tolerant plants, and that the shade tolerance nature is sustained under field conditions.

We used an Arabidopsis β-glucosidase AtBG1 to engineer a crop with elevated active ABA levels, and developed transgenic creeping bentgrass with enhanced drought tolerance and dwarf phenotype.

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