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FTSZ and MIN proteins play important roles in plastid division. Having previously identified FTSZ genes in Chlamydomonas reinhardtii, we have now isolated the nucleus-encoded MIND and MINE1 genes from this species. Sequence analyses showed that MIND is highly conserved, while MINE1 is less well conserved. Both proteins were localized to chloroplasts, probably due to their N-terminal transit peptides. The transcription levels of FTSZ and MIN genes in synchronous cultures of C. reinhardtii, in which the chloroplasts divided synchronously with their host cells, were examined. Semi-quantitative reverse transcription PCR (RT-PCR) analyses showed that mRNA abundance displayed a circadian pattern under light-dark cycles and continuous light and dark conditions. Maximal mRNA levels correlated with cell division, and thus, chloroplast division. This work indicates that plastid division is regulated by the circadian expression of FTSZ and MIN genes.

Microarray analysis is used to identify transcriptional targets. However, the direct targets of transcription factors cannot be distinguished from indirect ones; further, genes with low-expression levels cannot be identified by this method. In the present study, we exploit the cis -element dehydration-responsive element (DRE) that is known to be responsible for the transcription of DRE binding factor 1 (DREB1) targets in the promoter region of all Arabidopsis genes. Putative targets whose promoters contain the elements were verified by both microarray and reverse transcription-polymerase chain reaction (RT-PCR) analysis. Five new DREB1/CBF direct targets were identified. Compared with traditional microarray analysis, our method is convenient and cost-effective for identifying the downstream targets of transcription factors.

Physcomitrella patens is well known because of its importance in the study of plant systematics and evolution. The tolerance of P. patens for high-salinity environments also makes it an ideal candidate for studying the molecular mechanisms by which plants respond to salinity stresses. We measured changes in the proteome of P. patens gametophores that were exposed to high-salinity (250, 300, and 350 mM NaCl) using two-dimensional gel electrophoresis (2-DE) via liquid chromatography-tandem mass spectrometry (LC-MS/MS). Sixty-five protein spots were significantly altered by exposure to the high-salinity environment. Among them, 16 protein spots were down-regulated and 49 protein spots were up-regulated. These proteins were associated with a variety of functions, including energy and material metabolism, protein synthesis and degradation, cell defense, cell growth/division, transport, signal transduction, and transposons. Specifically, the up-regulated proteins were primarily involved in defense, protein folding, and ionic homeostasis. In summary, we outline several novel insights into the response of P. patens to high-salinity; (1) HSP70 is likely to play a significant role in protecting proteins from denaturation and degradation during salinity stress, (2) signaling proteins, such as 14-3-3 and phototropin, may work cooperatively to regulate plasma membrane H(+)-ATPase and maintain ion homeostasis, (3) an increase in photosynthetic activity may contribute to salinity tolerance, and (4) ROS scavengers were up-regulated suggesting that the antioxidative system may play a crucial role in protecting cells from oxidative damage following exposure to salinity stress in P. patens.

MinD is a ubiquitous ATPase that plays a crucial role in selection of the division site in eubacteria, chloroplasts, and probably Archaea. In four green algae, Mesostigma viride, Nephroselmis olivacea, Chlorella vulgaris and Prototheca wickerhamii, MinD homologues are encoded in the plastid genome. However, in Arabidopsis, MinD is a nucleus-encoded, chloroplast-targeted protein involved in chloroplast division, which suggests that MinD has been transferred to the nucleus in higher land plants. Yet the lateral gene transfer (LGT) of MinD from plastid to nucleus during plastid evolution remains poorly understood. Here, we identified a nucleus-encoded MinD homologue from unicellular green alga Chlamydomonas reinhardtii, a basal species in the green plant lineage. Overexpression of CrMinD in wild type E. coli inhibited cell division and resulted in the filamentous cell formation, clearly demonstrated the conservation of the MinD protein during the evolution of photosynthetic eukaryotes. The transient expression of CrMinD-egfp confirmed the role of CrMinD protein in the regulation of plastid division. Searching all the published plastid genomic sequences of land plants, no MinD homologues were found, which suggests that the transfer of MinD from plastid to nucleus might have occurred before the evolution of land plants.

Oligonucleotide microarrays were used to study the differences of gene expressions in high (H) and low (L) metastatic ovarian cancer cell lines and in normal ovarian tissues (C). Bioinformatics was used to identify novel genes and their functions as well as chromosomal localizations. A total of 409 genes were differentially expressed between the high and low metastatic ovarian cancer cell lines. Of them, 271 genes were up regulated (Signal Log Ratio[SLR] ≥1), and 138 genes were down regulated (SLR≤-1). Except one gene whose location was unknown, all these genes were localized randomly on all the chromosomes, with a majority of them localized to Chromosomes 1, 6, 2, 17, 3, 5 and 11. Chromosome 1 contained, 43 of them (10.7%), the most for a single chromosome. A total of 264 genes (64.7%) were localized on the short arm of the chromosome (q). Functional classification showed that the 104 (25.4%) genes coding for enzymes and enzyme regulators made up the largest functional group, followed by signal transduction activity genes (43, 10.5%), nucleic acid binding activity genes (42, 10.3%), and proteins binding activity genes (34, 8.3%). These four groups accounted for 54.5% of all the differentially expressed genes. In addition, the functions of 76 genes (18.6%) were unknown. Tumor metastasis is the result of a number of genes acting in concert. The four functional groups of genes classified among these genes and their abnormalities would be the focus of further studies on ovarian cancer metastasis.

To isolate Fe-deficient related (Fdr) genes, an expression cDNA library of 4.5×105 pfu/μg has been constructed from maize roots in iron-stress. 6 clones have been screened from the cDNA library by differential hybridization screening. It is proved that anFdr3 cDNA clone expressed stronger under iron-deficient condition than under iron-sufficient one by Northern blot and Western blot.

The dehydration-responsive element binding (DREB) transcription factors play central roles in regulating expression of stress-inducible genes under abiotic stresses. In the present work, PpDBF1 (Physcomitrella patens DRE-binding Factor1) containing a conserved AP2/ERF domain was isolated from the moss P. patens. Sequence comparison and phylogenetic analysis revealed that PpDBF1 belongs to the A-5 group of DREB transcription factor subfamily. The transcriptional activation activity and DNA-binding specificity of PpDBF1 were verified by yeast one-hybrid and electrophoretic mobility shift assay experiments, and its nuclear localization was demonstrated by particle biolisitics. PpDBF1 transcripts were accumulated under various abiotic stresses and phytohormones treatments in P. patens, and transgenic tobacco plants over-expressing PpDBF1 gained higher tolerance to salt, drought and cold stresses. These results suggest that PpDBF1 may play a role in P. patens as a DREB transcription factor, implying that similar regulating systems are conserved in moss and higher plants.