External Ca(2+) is essential for chloroplast movement induced by mechanical stimulation but not by light stimulation. (1/13)

In the fern Adiantum capillus-veneris, chloroplast movement is induced by mechanical stimulation as well as by light stimulation. Directional movement of both types depends on an actin-based motile system. To investigate the physiological relationship between mechanical and light signaling in the regulation of chloroplast movement, we examined the mechano-response of chloroplasts whose motility had been already restricted after photo-relocation. Chloroplast mechano-avoidance movement was induced under all of the photo-relocation conditions tested, indicating that mechano-specific signals generated by mechanical stimulation dominate over the light signals and reactivate the motility of chloroplasts. When the effects of external Ca(2+) on the induction of mechano- and light responses were examined, strikingly different requirements of external Ca(2+) were found for each. In medium without Ca(2+), the mechano-response was suppressed but no effects were observed on photo-response. Mechano-relocation movement of chloroplasts was inhibited by 100 microM lanthanum (La(3+)), a plasma membrane calcium channel blocker, and by 10 microM gadolinium (Gd(3+)), a stretch-activated channel blocker. However, the same concentrations of these drugs did not affect the photo-relocation movement at all. These results suggest that the influx of external Ca(2+) is crucial for the early signaling step of chloroplast mechano-relocation but not for that of photo-relocation. This is the first report showing the separation of signaling pathways in mechano- and photo-relocation of chloroplasts.  (+info)

Developmental anatomy and auxin response of lateral root formation in Ceratopteris richardii. (2/13)

The homosporous fern Ceratopteris richardii exhibits a homorhizic root system where roots originate from the shoot system. These shoot-borne roots form lateral roots (LRs) that arise from the endodermis adjacent to the xylem poles, which is in contrast to flowering plants where LR formation arises from cell division in the pericycle. A detailed study of the fifth shoot-borne root showed that one lateral root mother cell (LRMC) develops in each two out of three successive merophytes. As a result, LRs emerge alternately in two ranks from opposite positions on a parent root. From LRMC initiation to LR emergence, three developmental stages were identified based on anatomical criteria. The addition of auxins (either indole-3-acetic acid or indole-3-butyric acid) to the growth media did not induce additional LR formation, but exogenous applications of both auxins inhibited parent root growth rate. Application of the polar auxin-transport inhibitor N-(1-naphthyl)phthalamic acid (NPA) also inhibited parent root growth without changing the LR initiation pattern. The results suggest that LR formation does not depend on root growth rate per se. The result that exogenous auxins do not promote LR formation in C. richardii is similar to reports for certain species of flowering plants, in which there is an acropetal LR population and the formation of the LRs is insensitive to the application of auxins. It also may indicate that different mechanisms control LR development in non-seed vascular plants compared with angiosperms, taking into consideration the long and independent evolutionary history of the two groups.  (+info)

A systemic gene silencing method suitable for high throughput, reverse genetic analyses of gene function in fern gametophytes. (3/13)

BACKGROUND: Ceratopteris richardii is a useful experimental system for studying gametophyte development and sexual reproduction in plants. However, few tools for cloning mutant genes or disrupting gene function exist for this species. The feasibility of systemic gene silencing as a reverse genetics tool was examined in this study. RESULTS: Several DNA constructs targeting a Ceratopteris protoporphyrin IX magnesium chelatase (CrChlI) gene that is required for chlorophyll biosynthesis were each introduced into young gametophytes by biolistic delivery. Their transient expression in individual cells resulted in a colorless cell phenotype that affected most cells of the mature gametophyte, including the meristem and gametangia. The colorless phenotype was associated with a 7-fold decrease in the abundance of the endogenous transcript. While a construct designed to promote the transient expression of a CrChlI double stranded, potentially hairpin-forming RNA was found to be the most efficient in systemically silencing the endogenous gene, a plasmid containing the CrChlI cDNA insert alone was sufficient to induce silencing. Bombarded, colorless hermaphroditic gametophytes produced colorless embryos following self-fertilization, demonstrating that the silencing signal could be transmitted through gametogenesis and fertilization. Bombardment of young gametophytes with constructs targeting the Ceratopteris filamentous temperature sensitive (CrFtsZ) and uroporphyrin dehydrogenase (CrUrod) genes also produced the expected mutant phenotypes. CONCLUSION: A method that induces the systemic silencing of target genes in the Ceratopteris gametophyte is described. It provides a simple, inexpensive and rapid means to test the functions of genes involved in gametophyte development, especially those involved in cellular processes common to all plants.  (+info)

Profile and analysis of gene expression changes during early development in germinating spores of Ceratopteris richardii. (4/13)

Analysis of an expressed sequence tag library with more than 5,000 sequences from spores of the fern Ceratopteris richardii reveals that more than 3,900 of them represent distinct genes, and almost 70% of these have significant similarity to Arabidopsis (Arabidopsis thaliana) genes. Eight genes are common between three very different dormant plant systems, Ceratopteris spores, Arabidopsis seeds, and Arabidopsis pollen. We evaluated the pattern of mRNA abundance over the first 48 h of spore development using a microarray of cDNAs representing 3,207 distinct genes of C. richardii and determined the relative levels of RNA abundance for 3,143 of these genes using a Bayesian method of statistical analysis. More than 900 of them (29%) show a significant change between any of the five time points analyzed, and these have been annotated based on their sequence similarity with the Arabidopsis proteome. Novel data arising from these analyses identify genes likely to be critical for the germination and subsequent early development of diverse cells and tissues emerging from dormancy.  (+info)

Nitric oxide and cGMP signaling in calcium-dependent development of cell polarity in Ceratopteris richardii. (5/13)

Single-celled spores of the fern Ceratopteris richardii undergo gravity-directed cell polarity development that is driven by polar calcium currents. Here we present results that establish a role for nitric oxide (NO)/cGMP signaling in transducing the stimulus of gravity to directed polarization of the spores. Application of specific NO donors and scavengers inhibited the calcium-dependent gravity response in a dose-dependent manner. The effects of NO donor exposure were antagonized by application of NO scavenger compounds. Similarly, the guanylate cyclase inhibitors 6-anilino-5,8-quinolinedione and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin, and the phosphodiesterase inhibitor Viagra, which modulate NO-dependent cGMP levels in the cells, disrupted gravity-directed cell polarity in a dose-dependent manner. Viagra effects were antagonized by application of NO scavengers, consistent with the postulate that NO and cGMP are linked in the signaling pathway. To identify other components of the signaling system we analyzed gene expression changes induced by Viagra treatment using microarrays and quantitative real-time reverse transcription-polymerase chain reaction. Preliminary microarray analysis revealed several genes whose expression was significantly altered by Viagra treatment. Three of these genes had strong sequence similarity to key signal transduction or stress response genes and quantitative real-time reverse transcription-polymerase chain reaction was used to more rigorously quantify the effects of Viagra on their expression in spores and to test how closely these effects could be mimicked by treatment with dibutyryl cGMP. Taken together our results implicate NO and cGMP as downstream effectors that help link the gravity stimulus to polarized growth in C. richardii spores. Sequence data from this article can be found in the GenBank/EMBL data libraries under accession numbers BE 640669 to BE 643506, BQ 086920 to BQ 087668, and CV 734654 to CV 736151.  (+info)

The evolutionarily conserved family of cyanovirin-N homologs: structures and carbohydrate specificity. (6/13)

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Genome-scale cluster analysis of replicated microarrays using shrinkage correlation coefficient. (7/13)

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Asanoa hainanensis sp. nov., isolated from rhizosphere soil of Acrostichum speciosum in a mangrove, and emended description of the genus Asanoa. (8/13)

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