Heat shock transcription factors (Hsfs) are the central regulators of the heat shock (HS) stress response in all eukaryotic organisms. HsfA2 is one of the Arabidopsis class A Hsfs, and the induction of HsfA2 expression in response to HS stress is highest among all 21 Arabidopsis Hsfs. In this study, it is reported that basal and acquired thermotolerance was significantly enhanced in high-level HsfA2-overexpressed transgenic lines (El2Omega::HsfA2) in comparison with wild-type plants. By contrast, the dominant negative mutants of HsfA2 (El2Omega::HsfA2DeltaC264) plants displayed reduced thermotolerance. These results indicate that the HsfA2 gene plays a role in the HS stress response. Microarray analysis of the El2Omega::HsfA2 plants identified putative target genes, which included HS stress-inducible genes and other stress-responsive genes. Salt and osmotic stress induced HsfA2 gene expression. In fact, the El2Omega::HsfA2 plants showed enhanced tolerance to these stresses, suggesting that HsfA2 was involved in multiple stress tolerance. El2Omega::HsfA2 plants showed accelerated callus growth from root explants compared with the wild type, unlike the El2Omega::HsfA2DeltaC264 plants whose growth was delayed. These observations suggest that HsfA2 plays, in addition to its role in stress tolerance, an important role in cell proliferation.

This study investigated the regulatory mechanism of rapid and transient induction of a transcriptional repressor ERF3 gene by wounding in tobacco (Nicotiana tabacum) leaves. Deletion and mutation analysis of the promoter region have suggested that the proximal W boxes (TGAC(C/T)) and a GCC box, respectively, may be involved in the positive and negative regulation of wound-induced expression of the ERF3 gene. Electrophoretic mobility shift assays indicated that wounding enhanced the specific binding activity of nuclear factors to the W boxes. NtWRKY1, -2, and -4, which are tobacco group I WRKYs, interacted specifically with the W boxes and activated transcription via the W boxes. On the other hand, deletion of the GCC box from NsERF3 promoter-GUS reporter gene caused a delay in down-regulation of transcription after wound induction. In addition, ERF3 repressed transcription via the NsERF3 promoter activated by NtWRKYs. These results suggest the possible involvement of NtWRKYs and autorepression in the rapid and transient expression of the ERF3 gene by wounding.

The FAD7 gene, a gene for a chloroplast w-3 fatty acid desaturase, is responsible for the trienoic fatty acid (TA) formation in leaf tissues. The TA content of the leaf tissue of the 25°C-grown transgenic tobacco (Nicotiana tabacum cv SR1) plants, in which the FAD7 gene from Arabidopsis thaliana was overexpressed, increased uniformly by about 10%. Fatty acid unsaturation in all major leaf polar lipid species increased in the 25OC-grown FAD7 transformants but was approximately the same between the control plants and the FAD7 transformants when grown at 15°C. Therefore, the overexpression of the exogenous FAD7 gene leads to the same consequence in the tobacco plants as the low-temperature-induced TA production that may be catalyzed by an endogenous, temperatureregulated chloroplast w-3 fatty acid desaturase. In the 25°C-grown control plants, the chilling treatment caused symptoms of leaf chlorosis and suppression of leaf growth. The 25°C-grown FAD7 transgenic plants conferred alleviation of these chilling-induced symptoms. A reduction of the chilling injury similar to that of the FAD7 transformants was also observed in the 15°C-preincubated control plants. These results indicate that the increased TA production during chilling acclimation is one of the prerequisites for the normal leaf development at low, nonfreezing temperatures.

Many insects exhibit stereotypic instinctive behavior [1-3], but the underlying neural mechanisms are not well understood due to difficulties in detecting brain activity in freely moving animals. Immediate early genes (IEGs), such as c-fos, whose expression is transiently and rapidly upregulated upon neural activity, are powerful tools for detecting behavior-related neural activity in vertebrates [4, 5]. In insects, however, this powerful approach has not been realized because no conserved IEGs have been identified. Here, we identified Hr38 as a novel IEG that is transiently expressed in the male silkmoth Bombyx mori by female odor stimulation. Using Hr38 expression as an indicator of neural activity, we mapped comprehensive activity patterns of the silkmoth brain in response to female sex pheromones. We found that Hr38 can also be used as a neural activity marker in the fly Drosophila melanogaster. Using Hr38, we constructed a neural activity map of the fly brain that partially overlaps with fruitless (fru)-expressing neurons in response to female stimulation. These findings indicate that Hr38 is a novel and conserved insect neural activity marker gene that will be useful for a wide variety of neuroethologic studies.