A Nucleus-encoded Topological Specificity Factor PpMinE in Physcomitrella patens has Conserved Function Similar to Its Chloroplast-encoded Ancestor

A nucleus-encoded MinE gene, designated PpMinE, from Physcomitrella patens was identified using RT-PCR. The presence of both N- and C-terminal extensions in PpMinE protein suggested its cyanobacterial origin. The transient expression of PpMinE using green fluorescent protein fusion in tobacco （Nicotiana tabacum L.） indicated that the PpMinE was a chloroplast-targeted protein. Overexpression of PpMinE in Escherichia coli caused division site misplacement and minicell formation, suggesting evolutionary functional conservation of MinE during plant phylogenesis. According to the phylogenetic tree, PpMinE protein has a close relationship with the highland plants, which suggests that the transfer events of MinE gene from plastid to nucleus might have occurred before the origin of the land plants.

Heterologous expression of Hp BHY and Cr BKT increases heat tolerance in Physcomitrella patens

Heat stress can restrict plant growth,development,and crop yield.As essential plant antioxidants,carotenoids play significant roles in plant stress resistance.b-carotene hydroxylase(BHY)and b-carotene ketolase(BKT),which catalyze the conversions of b-carotene to zeaxanthin and b-carotene to canthaxanthin,respectively,are key enzymes in the carotenoid biosynthetic pathway,but little is known about their potential functions in stress resistance.Here,we investigated the roles of b-carotene hydroxylase and b-carotene ketolase during heat stress in Physcomitrella patens through expressing a b-carotene ketolase gene from Chlamydomonas reinhardtii(Cr BKT)and a b-carotene hydroxylase gene from Haematococcus pluvialis(Hp BHY)in the moss P.patens.In transgenic moss expressing these genes,carotenoids content increased(especially lutein content),and heat stress tolerance increased,with reduced leafy tissue necrosis.To investigate the mechanism of this heat stress resistance,we measured various physiological indicators and found a lower malondialdehyde level,higher peroxidase and superoxide dismutase activities,and higher endogenous abscisic acid and salicylate content in the transgenic plants in response to high-temperature stress.These results demonstrate that Cr BKT and Hp BHY increase plant heat stress resistance through the antioxidant and damage repair metabolism,which is related to abscisic acid and salicylate signaling.

The effects of methanol extract of cleistopholis patens on the reproductive system of female Wistar rats

Objective:In Port Harcourt and its environs,extracts of Cleistopholis patens are used by traditional medicine healers for the treatment of menstrual irregularities and other gynaecological disorders.The objective of this study was therefore to determine the effects of orally administered methanol extract of the stem bark of Cleistopholis patens on the reproductive organs of non-pregnant albino(Wistar) rats.Methods:3g/kg(low dose) and 6g/kg(high dose) of the extract were administered orally,daily to two different groups of animals,respectively, over a period of 28 days.A third(control) group of animals received distilled water only,orally over the same period.Five animals from each of the groups were sacrificed on day 8,15 and 29.Venous blood samples and reproductive organs respectively were taken from each group of sacrificed animals for hormonal and histopathological analysis.Results:Results of the hormonal assay revealed a general increase in the levels of Follicle Stimulating Hormone(FSH),Luteinizing Hormone(LH),progesterone,and estrogen.The highest levels were noticed in the animals sacrificed on the 29th day(LH =5.48±0.04 IU/L;FSH =3.80±0.00 IU/ L;Progesterone =7.14±0.15 nmol/L;Estrogen = 0.168±0.002 nmol/L).These increases were statistically significant compared to those of the control animals(LH =2.90±0.00 IU /L;FSH = 1.28±0.02 IU/L; Progesterone = 3.80±0.00 nmol/L;Estrogen = 0.130±0.002 nmol/L;P【0.05),and were also dose dependent. Results of the histopathological studies showed presence of chronic inflammatory cells in the tissues of the fallopian tubes and uterus on the 29th day.However,no changes were observed in the ovaries.Conclusion: The administration of the extract produced a dose and time-dependent increase in FSH,LH,progesterone and estrogen levels.We postulate that these observed effects may have been induced by the phytoestrogens (known to have 1/1 000 th of the efficacy of natural oestrogens) in the extract.The hormonal and histopathological changes may explain the effects described by patients following ingestion of extracts of this plant in traditional medical practice.However,it remains to be determined if these effects are harmful or beneficial in disease conditions.

Maintenance of Normal Stress Tolerance in the Moss Physcomitrella patens Lacking Chloroplastic CuZn-Superoxide Dismutase

Superoxide dismutases (SODs) catalyze the dismutation of superoxide and play an important role in reducing oxidative stress in plants. Based on in-gel SOD activity staining, chloroplasts of the moss Physcomitrella patens have two CuZn-SODs as the major SOD isozymes and minor SODs, including a Fe-SOD and two Mn-SODs. To investigate the contribution of chloroplastic SODs to stress tolerance in P. patens, we generated a double mutant lacking chloroplastic CuZn-SOD genes. The mutant did not show any differences in comparison to the wild type based on the growth of protonemata on normal and high-salt media, extractable activities of the other SODs after culture on normal and high-salt media, and inhibition of Fv/Fm under stress conditions (high-salt, high-light, and high-temperature). These results indicate that chloroplastic CuZn-SODs do not play a principal role in oxidative stress tolerance in chloroplasts under the investigated conditions. These findings explain the previously reported unusual response of P. patens to copper deficiency, in which chloroplastic CuZn-SODs are preferentially inactivated but cytosolic CuZn-SODs are unaffected.

Gas Chromatography-Mass Spectrometry Study from the Leaves Fractions Obtained of <i>Vernonanthura patens</i>(Kunth) H. Rob

Preliminary phytochemical study of methanol extracts from Vernonanthura patens’s leaves located in Marcabelí (El Oro province), Ecuador. The methodology consisted of chromatographic column separations with increasing polarity solvents and the analysis of fractions by Gas Chromatography-Mass Spectrometry coupled system (GC-MS). The structure of 53 compounds was proposed. Analyzed V. patens species showed the presence of terpene and aliphatic hydrocarbons, free fatty acids and their methyl and ethyl esters, oxygen sesqui, triterpenoids and sugars. For ecuadorian species, there are no records of chemical studies.

Studies of the Volatile Compounds Present in Leaves, Stems and Flowers of <i>Vernonanthura patens</i>(Kunth) H. Rob

The study of the volatile components of the leaves, stems and flowers of Vernonanthura patens is discussed. A micro solid-phase extraction at constant temperature with a dimethylsiloxane fiber of 100 μm was performed. The compounds extracted were analyzed by gas chromatography coupled to mass spectrometry (GC-MS). 7 monoterpenes structures were assigned to leaves, and three to stems, these compounds were not detected in the flowers with the configuration of the system used. 17 sesquiterpenes were identified in the leaves;6 in stems and 2 in flowers, finding coincidence in some of them. The major components were α-humulene in leaves, bergamotene in stems and caryophyllene in flowers.

A Transcriptome Atlas of Physcomitrella patens Provides Insights into the Evolution and Development of Land Plants

Identifying the genetic mechanisms that underpin the evolution of new organ and tissue systems is an aim of evolutionary developmental biology. Comparative functional genetic studies between angiosperms and bryophytes can define those genetic changes that were responsible for developmental innovations. Here, we report the generation of a transcriptome atlas covering most phases in the life cycle of the model bryo- phyte Physcomitrella patens, including detailed sporophyte developmental progression. We identified a comprehensive set of sporophyte-specific transcription factors, and found that many of these genes have homologs in angiosperms that function in developmental processes such as flowering and shoot branching. Deletion of the PpTCP5 transcription factor results in development of supernumerary sporangia attached to a single seta, suggesting that it negatively regulates branching in the moss sporophyte. Given that TCP genes repress branching in angiosperms, we suggest that this activity is ancient. Finally, compar- ison of P. patens and Arabidopsis thaliana transcriptomes led us to the identification of a conserved core of transcription factors expressed in tip-growing cells. We identified modifications in the expression patterns of these genes that could account for developmental differences between P. patens tip-growing cells and A. thaliana pollen tubes and root hairs.

Targeted Gene Knockouts Reveal Overlapping Functions of the Five Physcomitrella patens FtsZ Isoforms in Chloroplast Division, Chloroplast Shaping, Cell Patterning, Plant Development, and Gravity Sensing

Chloroplasts and bacterial cells divide by binary fission. The key protein in this constriction division is FtsZ, a self-assembling GTPase similar to eukaryotic tubulin. In prokaryotes, FtsZ is almost always encoded by a single gene, whereas plants harbor several nuclear-encoded FtsZ homologs. In seed plants, these proteins group in two families and all are exclusively imported into plastids. In contrast, the basal land plant Physcomitrella patens, a moss, encodes a third FtsZ family with one member. This protein is dually targeted to the plastids and to the cytosol. Here, we report on the targeted gene disruption of all ftsZ genes in R patens. Subsequent analysis of single and double knockout mutants revealed a complex interaction of the different FtsZ isoforms not only in plastid division, but also in chloroplast shaping, cell patterning, plant development, and gravity sensing. These results support the concept of a plastoskeleton and its functional integration into the cytoskeleton, at least in the moss R patens.

Computational Analysis of Drought Stress-Associated miRNAs and miRNA Co-Regulation Network in Physcomitrella patens

miRNAs are non-coding small RNAs that involve diverse biological processes. Until now, little is known about their roles in plant drought resistance. Physcomitrella patens is highly tolerant to drought; however, it is not clear about the basic biology of the traits that contribute P. patens this important character. In this work, we discovered 16 drought stress-associated miRNA （DsAmR） families in P. patens through computational analysis. Due to the possible discrepancy of expression periods and tissue distributions between potential DsAmRs and their targeting genes, and the existence of false positive results in computational identification, the prediction results should be examined with further experimental validation. We also constructed an miRNA co-regulation network, and identi- fied two network hubs, miR902a-Sp and miR414, which may play important roles in regulating drought-resistance traits. We distributed our results through an online database named ppt-miRBase, which can be accessed at http：/Poioinfor.cnu.edu.cn/ppt_miRBase/index.php. Our methods in finding DsAmR and miRNA co-regulation network showed a new direction for identifying miRNA functions.

Target deletion of the AAA ATPase PpCDC48II in Physcomitrella patens results in freezing sensitivity after cold acclimation

CDC48 is a highly conserved protein in eukaryotes and belongs to the AAA （ATPase associated with a variety of cellular activities） superfamily. It can interact with many different cofactors and form protein complexes that play important roles in various cellular processes. According to the Physcomitrella patens database, one member of the ATPases, the cell cycle gene PpCDC4811, was cloned. PpCDC48II contains two typical ATPase modules and is highly homologous to AtCDC48A. PpCDC4811 was up-regulated in mRNA levels after incubation at 0~C for 36 and 72 h. To further elucidate protein function, we disrupted the PpCDC4811 gene by transforming P. patens with the corresponding linear genomic sequences. When treated to the same freezing stress, it was found that PpCDC4811 knockout plants were less resistant to freezing treatment than wild type after acclimation. This suggested that PpCDC481I was an essential gene for low-temperature-induced freezing tolerance in P. patens cells.

小立碗藓细胞色素P450基因CYP73A49的克隆与功能分析

本研究克隆了一个小立碗藓(Physcomitrella patens)P450基因CYP73A49,其cDNA全长1 629 bp,预测编码542个氨基酸。为了进一步研究其生物学功能,利用同源重组技术对CYP73A49基因实施定点突变,成功构建了能诱导其功能缺失的载体,并获得了苔藓的功能缺失突变体。

应用傅立叶变换回旋共振质谱对小立碗藓新蛋白的序列分析

Two new proteins from physcomitrella patens were sequenced by nanoLC-FT-ICR tandem mass spectrometry.Eight and seven peptides were sequenced for spot 303 and spot 413 respectively.Database search was performed through the search engine Mascot (www.matrixscience.com) by MS/MS ion search program and Sequence Tag program.Blast was performed too.No statistical significant results were obtained from database search.The reliable amino acid sequences can be used for gene clone due to high mass accuracy.This research indicates that nanoLC-FT-ICR tandem mass spectrometric technique is powerful tools for new protein sequence analysis and will play an important role in plant proteomics research.

Between a Rock and a Dry Place： The Water-Stressed Moss

The earliest land plants faced a suite of abiotic stresses largely unknown to their aquatic algal ancestors. The descendants of these plants evolved two general mechanisms for survival in the relatively arid aerial environment. While the vascular plants or ＇tracheophytes＇ developed tissue specializations to transport and retain water, the other main lineages of land plants, the bryophytes, retained a simple, nonvascular morphology. The bryophytes--mosses, hornworts, and liverworts--continually undergo a co-equilibration of their water content with the surrounding environment and rely to a great extent on intrinsic cellular mechanisms to mitigate damage due to water stress. This short review will focus on the cellular and molecular responses to dehydration and rehydration in mosses, and offer insights into general plant responses to water stress.