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1.
In order to determine the degree of tolerance of the moss Physcomitrella patens to different abiotic stress conditions, we examined its tolerance against salt, osmotic and dehydration stress. Compared to other plants like Arabidopsis thaliana, P. patens exhibits a high degree of abiotic stress tolerance, making it a valuable source for the identification of genes effecting the stress adaptation. Plants that had been treated with NaCl tolerated concentrations up to 350 mM. Treatments with sorbitol revealed that plants are able to survive concentrations up to 500 mM. Furthermore, plants that had lost 92% water on a fresh-weight basis were able to recover successfully. For molecular analyses, a P. patens expressed sequence tag (EST) database was searched for cDNA sequences showing homology to stress-associated genes of seed plants and bacteria. 45 novel P. patens genes were identified and subjected to cDNA macroarray analyses to define their expression pattern in response to water deficit. Among the selected cDNAs, we were able to identify a set of genes that is specifically up-regulated upon dehydration. These genes encode proteins exerting their function in maintaining the integrity of the plant cell as well as proteins that are known to be members of signaling networks. The identified genes will serve as molecular markers and potential targets for future functional analyses. 相似文献
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Juan Pablo Oliver Alexandra Castro Carina Gaggero Tomas Cascón Eric A. Schmelz Carmen Castresana Inés Ponce de León 《Planta》2009,230(3):569-579
The moss Physcomitrella patens (P. patens) is a useful model to study abiotic stress responses since it is highly tolerant to drought, salt and osmotic stress. However,
very little is known about the defense mechanisms activated in this moss after pathogen assault. In this study, we show that
P. patens activated multiple and similar responses against Pythium irregulare and Pythium debaryanum, including the reinforcement of the cell wall, induction of the defense genes CHS, LOX and PAL, and accumulation of the signaling molecules jasmonic acid (JA) and its precursor 12-oxo-phytodienoic acid (OPDA). However,
theses responses were not sufficient and infection could not be prevented leading to hyphae colonization of moss tissues and
plant decay. Pythium infection induced reactive oxygen species production and caused cell death of moss tissues. Taken together, these data indicate
that Pythium infection activates in P. patens common responses to those previously characterized in flowering plants. Microscopic analysis also revealed intracellular
relocation of chloroplasts in Pythium-infected tissues toward the infection site. In addition, OPDA, JA and its methyl ester methyl jasmonate induced the expression
of PAL. Our results show for the first time JA and OPDA accumulation in a moss and suggest that this defense pathway is functional
and has been maintained during the evolution of plants.
Authors Juan Pablo Oliver and Alexandra Castro contributed equally to this work. 相似文献
3.
Jiang SY Bachmann D La H Ma Z Venkatesh PN Ramamoorthy R Ramachandran S 《Plant molecular biology》2007,65(4):385-402
The availability of diversified germplasm resources is the most important for developing improved rice varieties with higher
seed yield or tolerance to various biotic or abiotic stresses. Here we report an efficient tool to create increased variations
in rice by maize Ac/Ds transposon (a gene trap system) insertion mutagenesis. We have generated around 20,000 Ds insertion rice lines of which majority are homozygous for Ds element. We subjected these lines to phenotypic and abiotic stress screens and evaluated these lines with respect to their
seed yields and other agronomic traits as well as their tolerance to drought, salinity and cold. Based on this evaluation,
we observed that random Ds insertions into rice genome have led to diverse variations including a range of morphological and conditional phenotypes.
Such differences in phenotype among these lines were accompanied by differential gene expression revealed by GUS histochemical
staining of gene trapped lines. Among the various phenotypes identified, some Ds lines showed significantly higher grain yield compared to wild-type plants under normal growth conditions indicating that
rice could be improved in grain yield by disrupting certain endogenous genes. In addition, several 1,000s of Ds lines were subjected to abiotic stresses to identify conditional mutants. Subsequent to these screens, over 800 lines responsive
to drought, salinity or cold stress were obtained, suggesting that rice has the genetic potential to survive under abiotic
stresses when appropriate endogenous genes were suppressed. The mutant lines that have higher seed yielding potential or display
higher tolerance to abiotic stresses may be used for rice breeding by conventional backcrossing combining with molecular marker-assisted
selection. In addition, by exploiting the behavior of Ds to leave footprints upon remobilization, we have shown an alternative strategy to develop new rice varieties without foreign
DNA sequences in their genome.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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The ATPases associated with various cellular activities (AAA) proteins are widespread in living organisms. Some of the AAA-type
ATPases possess metalloprotease activities. Other members constitute the 26S proteasome complexes. In recent years, a few
AAA members have been implicated in vesicle-mediated secretion, membrane fusion, cellular organelle biogenesis, and hypersensitive
responses (HR) in plants. However, the physiological roles and biochemical activities of plant AAA proteins have not yet been
defined at the molecular level, and regulatory mechanisms underlying their functions are largely unknown. In this study, we
showed that overexpression of an Arabidopsis gene encoding a mitochondrial AAA protein, ATPase-in-Seed-Development (ASD), induces morphological and anatomical defects
in seed maturation. The ASD gene is expressed at a high level during the seed maturation process and in mature seeds but is repressed rapidly in germinating
seeds. Transgenic plants overexpressing the ASD gene are morphologically normal. However, seed formation is severely disrupted in the transgenic plants. The ASD gene is
induced by abiotic stresses, such as low temperatures and high salinity, in an abscisic acid (ABA)-dependent manner. The ASD
protein possesses ATPase activity and is localized into the mitochondria. Our observations suggest that ASD may play a role
in seed maturation by influencing mitochondrial function under abiotic stress. 相似文献
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Plant productivity is greatly influenced by various environmental stresses, such as high salinity and drought. Earlier, we
reported the isolation of topoisomerase 6 homologs from rice and showed that over expression of OsTOP6A3 and OsTOP6B confers abiotic stress tolerance in transgenic Arabidopsis plants. In this study, we have assessed the function of nuclear-localized topoisomerase 6 subunit A homolog, OsTOP6A1, in
transgenic Arabidopsis plants. The over expression of OsTOP6A1 in transgenic Arabidopsis plants driven by cauliflower mosaic virus-35S promoter resulted in pleiotropic effects on plant growth and development. The
transgenic Arabidopsis plants showed reduced sensitivity to stress hormone, abscisic acid (ABA), and tolerance to high salinity and dehydration
at the seed germination; seedling and adult stages as reflected by the percentage of germination, fresh weight of seedlings
and leaf senescence assay, respectively. Concomitantly, the expression of many stress-responsive genes was enhanced under
various stress conditions in transgenic Arabidopsis plants. Moreover, microarray analysis revealed that the expression of a large number of genes involved in various processes
of plant growth and development and stress responses was altered in transgenic plants. Although AtSPO11-1, the homolog of
OsTOP6A1 in Arabidopsis, has been implicated in meiotic recombination; the present study demonstrates possible additional role of OsTOP6A1 and provides
an effective tool for engineering crop plants for tolerance to different environmental stresses.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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Since plants cannot move to avoid stress, they have sophisticated acclimation mechanisms against a variety of abiotic stresses.
The phytohormone abscisic acid (ABA) plays essential roles in abiotic stress tolerances in land plants. Therefore, it is interesting
to address the evolutionary origins of ABA metabolism and its signaling pathways in land plants. Here, we focused on 48 ABA-related
Arabidopsis thaliana genes with 11 protein functions, and generated 11 orthologous clusters of ABA-related genes from A. thaliana, Arabidopsis lyrata, Populus trichocarpa, Oryza sativa, Selaginella moellendorffii, and Physcomitrella patens. Phylogenetic analyses suggested that the common ancestor of these six species possessed most of the key protein functions
of ABA-related genes. In two species (A. thaliana and O. sativa), duplicate genes related to ABA signaling pathways contribute to the expression variation in different organs or stress
responses. In particular, there is significant expansion of gene families related to ABA in evolutionary periods associated
with morphological divergence. Taken together, these results suggest that expansion of the gene families related to ABA signaling
pathways may have contributed to the sophisticated stress tolerance mechanisms of higher land plants. 相似文献