Enzymatic characterization and thermostability improvement of an acidophilic endoxylanase PphXyn11 from Paenibacillus physcomitrellae XB.

GH11 enzyme is known to be specific and efficient for the hydrolysis of xylan. It has been isolated from many microorganisms, and its enzymatic characteristics and thermostability vary between species. In this study, a GH11 enzyme PphXyn11 from a novel xylan-degrading strain of Paenibacillus physcomitrellae XB was characterized, and five mutants were constructed to try to improve the enzyme's thermostability. The results showed that PphXyn11 was an acidophilic endo-ß-1,4-xylanase with the optimal reaction pH of 3.0-4.0, and it could deconstruct different kinds of xylan substrates efficiently, such as beechwood xylan, wheat arabinoxylan and xylo-oligosaccharides, to produce xylobiose and xylotriose as the main products at the optimal reaction temperature of 40 °C. Improvement of the thermal stability of PphXyn11 using site-directed mutagenesis revealed that three mutants, W33C/N47C, S127C/N174C and S49E, designed by adding the disulfide bonds at the N-terminal, C-terminal and increasing the charged residues on the surface of PphXyn11 respectively, could increase the enzymatic activity and thermal stablility significantly and make the optimal reaction temperature reach 50 °C. Molecular dynamics simulations as well as computed the numbers of salt bridges and hydrogen bonds indicated that the protein structures of these three mutants were more stable than the wild type, which provided theoretical support for their improved thermal stability. Certainly, further research is necessary to improve the enzymatic characteristics of PphXyn11 to achieve the bioconversion of hemicellulosic biomass on an applicable scale.

Contributions and characteristics of two bifunctional GH43 ß-xylosidase /α-L-arabinofuranosidases with different structures on the xylan degradation of Paenibacillus physcomitrellae strain XB.

Xylan is one of the major polymeric hemicellulosic constituents of lignocellulosic biomass, and its effective utilization by microorganisms is crucial for the economical production of biofuels. In this study, Paenibacillus physcomitrellae XB exhibited different xylan degradation ability on different substrates of corncob xylan (CCX), oat spelt xylan (OSX), wheat flour arabinoxylan (AX) and beech wood xylan (BWX). The RT-QPCR result showed that two genes (Pph_0602 and Pph_2344) belonging to the glycoside hydrolase family 43 were up-regulated more than 5-fold on CCX and xylose. Substrate-specific assays with purified proteins Ppxyl43A (Pph_0602) and Ppxyl43B (Pph_2344) revealed that both exhibited ß-xylosidase activity toward the chromogenic substrate p-nitrophenyl-ß-D-xylopyranoside, and α-L-arabinofuranosidase activity toward p-nitrophenyl-α-L-arabinofuranoside, indicating their bifunctionality. By testing their degradation characteristics on different natural substrates, it was found that both Ppxyl43A and Ppxyl43B showed similar degradation ability on CCX and OSX. Both enzymes could hydrolyze xylohexaose and xylobiose completely to xylose, but could not hydrolyze BWX and AX, suggesting they mainly hydrolyze xylo-oligosaccharides by ß-xylosidase activity. Further analysis showed that both of them displayed very high pH stability and thermostability on the ß-xylosidase activity, but Ppxy143B exhibited wider pH and temperature ranges, higher pH and temperature stability, was less influenced by metal ions, and had a slower start-up response than Ppxyl43A. Given their predicted structure, it is likely that the enzymatic differences between Ppxyl43A and Ppxyl43B might be related to the extra C-terminus domain (GH43_C2) in Ppxyl43B, which could enhance the enzymatic stability while restricting the substrates' or metal ions' access to the active sites of Ppxyl43B. In conclusion, both Ppxyl43A and Ppxyl43B were ß-xylosidase/α-L-arabinofuranosidase bifunctional enzymes and might be useful in xylan biomass conversion, especially in the hydrolysis of xylo-oligosaccharides into xylose.

Physicochemical and functional characteristics of polysaccharides from okra extracted by using ultrasound at different frequencies.

In this study, single- (SFU) and dual-frequency (DFU) ultrasounds were used to extract polysaccharides from okra (Abelmoschus esculentus (L.) Moench) pods (OPSs), and the physicochemical characteristics, functional properties, and in vitro biological activities of the OPSs were comparatively evaluated. Results showed that ultrasonic extractions at different frequencies led to remarkable variations in extraction yields, chemical components, monosaccharide compositions, molecular weights (MWs), surface morphologies, and rheological properties of the OPSs but hardly affected their preliminary structural features and thermal stabilities. The OPS obtained through DFU at 40/60 kHz with the lowest MWs (0.85-14.93 × 105 Da) and highest polyphenol content (7.38%) as well as loosest network structures showed superior antioxidant, cholesterol absorption and nitrite ion absorption capacities than the other OPSs, and the OPS extracted through SFU at 20 kHz with the highest carboxylate content (76.08%), MWs (7.28-32.83 × 105 Da) and degree of esterification (30.7%) exhibited higher bile acid-binding capacity than the other OPSs.

Sphingobacterium athyrii sp. nov., a cellulose- and xylan-degrading bacterium isolated from a decaying fern (Athyrium wallichianum Ching).

Assessment of the bacterial diversity associated with a decaying fern, Athyrium wallichianum Ching, revealed the presence of a novel bacterial strain named M46T. It was Gram-stain-negative, rod-shaped, non-motile and aerobic with cellulose and xylan degradation abilities. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain M46T was affiliated to the genus Sphingobacterium, exhibiting the highest sequence similarity of 97.9 % to Sphingobacterium ginsenosidimutans THG 07T, Sphingobacterium canadense CR11T and Sphingobacterium detergens6.2 ST. Multilocus sequence analysis (MLSA) based on concatenated sequences of the rpoB, cpn60 and 16S rRNA genes showed that strain M46T clustered together with S. canadense CR11T. The genome of strain M46T had a G+C content of 40.6 mol% and chromosome of 6 853 865 bp. Average nucleotide identity (ANI) between strain M46T and S. detergens 6.2 ST and S. siyangense SY1T was 85.1 and 78.1 %, respectively. DNA-DNA relatedness values among strain M46T and other closely related Sphingobacterium species were <70 %. ANI and DNA-DNA relatedness findings strongly supported M46T as a putative novel strain of Sphingobacterium. The predominant fatty acids of strain M46T were iso-C15 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and iso-C17 : 0 3-OH, and MK-7 was the dominant isoprenoid quinone. The polar lipid profile of strain M46T contained phosphatidylethanolamine as the dominant component, while minor amounts of phosphoglycolipid, one unidentified aminophospholipid, two unidentified phospholipids and four unidentified lipids were also detected. Based on 16S rRNA gene sequence similarities, MLSA results, genomic characteristics, and phenotypic and biochemotaxonomic analyses, strain M46T is considered to represent a novel species in the genus Sphingobacterium, for which the name Sphingobacterium athyrii sp. nov. is proposed. The type strain is M46T (=CGMCC 1.13466T=JCM 32543T).

Illumina sequencing of bacterial 16S rDNA and 16S rRNA reveals seasonal and species-specific variation in bacterial communities in four moss species.

In order to better understand the factors that influence bacterial diversity and community composition in moss-associated bacteria, a study of bacterial communities in four moss species collected in three seasons was carried out via high-throughput sequencing of 16S rDNA and 16S rRNA. Moss species included Cratoneuron filicinum, Pylaisiella polyantha, Campyliadelphus polygamum, and Grimmia pilifera, with samples collected in May, July, and October 2015 from rocks at Beijing Songshan National Nature Reserve. In total, the bacterial richness and diversity were high regardless of moss species, sampling season, or data source (DNA vs. RNA). Bacterial sequences were assigned to a total of 558 OTUs and 279 genera in 16 phyla. Proteobacteria and Actinobacteria were the two most abundant phyla, and Cellvibrio, Lapillicoccus, Jatrophihabitans, Friedmanniella, Oligoflexus, and Bosea the most common genera in the samples. A clustering algorithm and principal coordinate analysis revealed that C. filicinum and C. polygamum had similar bacterial communities, as did P. polyantha and G. pilifera. Metabolically active bacteria showed the same pattern in addition to seasonal variation: bacterial communities were most similar in summer and autumn, looking at each moss species separately. In contrast, DNA profiles lacked obvious seasonal dynamics. A partial least squares discriminant analysis identified three groups of samples that correlated with differences in moss species resources. Although bacterial community composition did vary with the sampling season and data source, these were not the most important factors influencing bacterial communities. Previous reports exhibited that mosses have been widely used in biomonitoring of air pollution by enriching some substances or elements in the moss-tag technique and the abundant moss associated bacteria might also be important components involved in the related biological processes. Thus, this survey not only enhanced our understanding of the factors which influence microbial communities in mosses but also would be helpful for better use and development of the moss-tag technique in the environmental biomonitoring.

Copper-Induced Spermatozoa Head Malformation Is Related to Oxidative Damage to Testes in CD-1 Mice.

The molecular mechanism for copper toxicity on spermatozoa quality in mice is not well understood. In a 4-week experiment, we challenged 24, 6-week-old male CD-1 mice with twice-a-week intraperitoneal copper chloride injections and evaluated spermatozoa quality, copper levels in the testes, serum testosterone, the expression of key antioxidant glutathione peroxidase 5 (GPx5), and the regulated androgen receptor (AR) in the mice testes. We compared these outcomes for four groups of six mice given doses of 0, 1.25, 2.5, 5.0 mg/kg weight copper chloride twice a week for 4 weeks. The mice demonstrated a copper increase spermatozoa head malformation in a dose-response manner. However, we observed no changes in spermatozoa viability and acrosome integrity in the ratio of mouse body weight to testes weight or in the histomorphology of the testes as the average copper level increased. Results of our RT-PCR assays, immunohistochemical tests, ELISA, and histochemistry analyses indicated that testis GPx5 expression was increased, AR expression in the testes was decreased, serum testosterone was decreased, and the activity of 3ß-hydroxysteroid dehydrogenase was decreased as the copper dose increased. In conclusion, these data show that sublethal exposure to copper induces spermatozoa head malformation and influences both mRNA and protein levels of GPx5 and AR which is related to copper resides in the testes.

Paenibacillus marchantiophytorum sp. nov., isolated from the liverwort Herbertus sendtneri.

A Gram-stain-positive, aerobic, motile, rod-shaped, endospore-forming bacterium, designated strain R55T, was isolated from the liverwort Herbertus sendtneri growing at Gawalong glacier, Tibet, and characterized by using a polyphasic taxonomic approach. The major fatty acids of strain R55T were anteiso-C15 : 0, C16 : 0 and iso-C16 : 0. Diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol were the predominant polar lipids and occurred along with two unidentified aminophospholipids, one unidentified phospholipid and one unidentified aminolipid. Strain R55T contained MK-7 as the dominant menaquinone and meso-diaminopimelic acid as the major diagnostic diamino acid in the cell-wall peptidoglycan. The G+C content of the genomic DNA was 36.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain R55T was affiliated to species of the genus Paenibacillus, and was related most closely to Paenibacillus ferrarius CY1T (97.1 % similarity). However, the DNA-DNA relatedness between this strain and strain R55T was only 44.1 %. Based on phenotypic, chemotaxonomic and phylogenetic properties, strain R55T is considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus marchantiophytorum sp. nov. is proposed. The type strain is R55T ( = CGMCC 1.15043T = DSM 29850T).

Paenibacillus herberti sp. nov., an endophyte isolated from Herbertus sendtneri.

Strain R33(T), an endophyte recovered from Herbertus sendtneri, was identified as representing a novel species of the genus Paenibacillus by using a polyphasic taxonomic approach. The novel strain was observed to be a Gram-stain positive, aerobic, rod-shaped, motile and endospore-forming bacterium. The major polar lipids of strain R33(T) were identified as diphosphatidylglycerol, phosphatidylethanolamine, along with lesser amounts of phosphatidylglycerol, three unidentified aminophospholipids, two unidentified phospholipids and two unidentified lipids. The predominant isoprenoid quinone was identified as MK-7. The major fatty acids (>8.0 %) were found to be anteiso-C15:0 (40.0 %), C16:1 ω11c (9.4 %), C16:1 ω7c alcohol (8.5 %) and C16:0 (8.2 %). The diamino acid found in the cell-wall peptidoglycan was meso-diaminopimelic acid. The G+C content of genomic DNA was determined to be 56.9 mol%. The 16S rRNA gene sequence similarities of strain R33(T) to other Paenibacillus species ranged from 91.6 to 97.2 %, with high similarities to Paenibacillus humicus PC-147(T) and Paenibacillus pasadenensis SAFN-007(T). The phylogenetic analyses based on 16S rRNA gene sequences and the partial rpoB gene confirmed that strain R33(T) belongs to the genus Paenibacillus. However, strain R33(T) shows differential molecular characteristics compared to other related Paenibacillus species based on 16S rDNA-RFLP analyses; the DNA-DNA relatedness values between strain R33(T) and P. humicus PC-147(T), and that between strain R33(T) and P. pasadenensis SAFN-007(T), were 35.0 ± 2.0 and 41.4 ± 0.9 %, respectively. Based on its phenotypic, chemotaxonomic and phylogenetic properties, strain R33(T) is considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus herberti is proposed (type strain R33(T) = CGMCC 1.15042(T) = DSM 29849(T)).

Chryseobacterium takakiae sp. nov., a member of the phylum Bacteroidetes isolated from Takakia lepidozioides.

A Gram-stain-negative, rod-shaped and non-endospore-forming bacterium, designated strain AG1-2(T), was isolated from Takakia lepidozioides collected from the Gawalong glacier in Tibet, China and characterized using a polyphasic taxonomic approach. The predominant fatty acids of strain AG1-2(T) were iso-C15 : 0 (36.0 %), iso-C17:0 3-OH (20.2 %), summed feature 9 (iso-C17:1ω9c and/or C16:0 10-methyl, 16.4%) and summed feature 3 (C16:1ω7c and/or C16:1ω6c, 11.1%). The major polar lipids were phosphatidylethanolamine, three unidentified aminolipids and two unidentified lipids. Strain AG1-2(T) contained MK-6 as the dominant menaquinone, and the genomic DNA G+C content was 37.3 mol%. The phylogenetic analysis based on the 16S rRNA gene sequences showed that strain AG1-2(T) was affiliated to species of the genus Chryseobacterium, and its closest related species were Chryseobacterium taiwanense Soil-3-27(T), Chryseobacterium hispalense AG13(T), Chryseobacterium camelliae THG C4-1(T) and Chryseobacterium taeanense PHA3-4(T) with a sequence similarity of 98.0, 97.8, 97.3 and 97.1%, respectively. However, the DNA-DNA relatedness values between these strains and strain AG1-2(T) were 29, 21, 21 and 45%, respectively. Based on phylogenetic inference and phenotypic data, strain AG1-2(T) is considered to represent a novel species of the genus Chryseobacterium, for which the name Chryseobacterium takakiae sp. nov. is proposed. The type strain is AG1-2(T) ( = CGMCC 1.12488(T) = DSM 26898(T)).

Chryseobacterium polytrichastri sp. nov., isolated from a moss (Polytrichastrum formosum), and emended description of the genus Chryseobacterium.

A Gram-stain negative, rod-shaped and non-endospore forming bacterium, designated strain YG4-6(T), was isolated from Polytrichastrum formosum collected from Gawalong glacier in Tibet, China and characterized by using a polyphasic taxonomic approach. The predominant fatty acids of strain YG4-6(T) were identified as iso-C15:0 (29.3 %), summed feature 3 (C16:1 ω7c and/or C16:1 ω6c as defined by MIDI, 23.5 %) and iso-C17:0 3-OH (16.5 %). The major polar lipids were found to consist of five unidentified aminolipids and three unidentified lipids. Strain YG4-6(T) was found to contain MK-6 as the dominant menaquinone and the G+C content of its genomic DNA was determined to be 37.3 mol%. The phylogenetic analysis based on 16S rRNA gene sequences showed that strain YG4-6(T) is affiliated to Chryseobacterium species, and its closest related species were Chryseobacterium aahli T68(T) (97.9 % sequence similarity), Chryseobacterium zeae JM-1085(T) (97.8 % sequence similarity), Chryseobacterium yeoncheonense DCY67(T) (97.6 % sequence similarity) and Chryseobacterium soldanellicola NBRC 100864(T) (97.2 % sequence similarity). However, the DNA-DNA relatedness values between these strains and strain YG4-6(T) were found to be clearly below 70 %. Based on the phylogenetic inference and phenotypic data, strain YG4-6(T) is considered to represent a novel species of the genus Chryseobacterium, for which the name Chryseobacterium polytrichastri sp. nov. is proposed. The type strain is YG4-6(T) (=CGMCC 1.12491(T) = DSM 26899(T)). An emended description of the genus Chryseobacterium is also proposed.

Mucilaginibacter polytrichastri sp. nov., isolated from a moss (Polytrichastrum formosum), and emended description of the genus Mucilaginibacter.

A Gram-staining-negative, rod-shaped, non-spore-forming bacterium, designated strain RG4-7(T), was isolated from the moss Polytrichastrum formosum collected from Gawalong glacier in Tibet, China, and characterized by using a polyphasic taxonomic approach. The predominant fatty acids of strain RG4-7(T) were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), iso-C15 : 0 and iso-C17 : 0 3-OH. The major polar lipids were phosphatidylethanolamine, one unidentified aminophospholipid, one unidentified phospholipid, two unidentified aminolipids and one unidentified lipid. Strain RG4-7(T) contained MK-7 as the dominant menaquinone and the G+C content of its genomic DNA was 39.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain RG4-7(T) was affiliated to species of the genus Mucilaginibacter, and its closest relative was Mucilaginibacter jinjuensis YC7004(T) (97.0 % sequence similarity). However, the DNA-DNA relatedness between this strain and strain RG4-7(T) was only 49.1±3.7 %. Based on phylogenetic inference and phenotypic data, strain RG4-7(T) is considered to represent a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter polytrichastri sp. nov. is proposed. The type strain is RG4-7(T) ( = CGMCC 1.12493(T) = DSM 26907(T)). An emended description of the genus Mucilaginibacter is also proposed.

Cnuella takakiae gen. nov., sp. nov., a member of the phylum Bacteroidetes isolated from Takakia lepidozioides.

A Gram-staining-negative, rod-shaped and non-spore-forming bacterium, designated strain RG1-1(T), was isolated from Takakia lepidozioides collected from Gawalong glacier in Tibet, China, and characterized by using a polyphasic taxonomic approach. The predominant fatty acids of strain RG1-1(T) were iso-C(15 : 0) (19.8%), summed feature 3 (C(16 : 1)ω7c and/or C(16 : 1)ω6c, 17.0%), C(16 : 0 (9.9)%) and iso-C(17 : 0) 3-OH (9.4%); its major polar lipids were phosphatidylethanolamine, four unidentified aminolipids, one unidentified phospholipid, one unidentified aminoglycolipid, one unidentified glycolipid, and three unidentified lipids. Strain RG1-1(T) contained MK-7 as the dominant menaquinone, and the G+C content of its genomic DNA was 49.1 mol%. Strain RG1-1(T) exhibited the highest 16S rRNA gene sequence similarity (91.8%) with Flavisolibacter ginsengiterrae Gsoil 492(T) and Flavisolibacter ginsengisoli Gsoil 643(T). Phylogenetic analysis showed that strain RG1-1(T) was a member of the family Chitinophagaceae, phylum Bacteroidetes. On the basis of 16S rRNA gene sequence analysis, and phenotypic and chemotaxonomic data, strain RG1-1(T) is considered to represent a novel species of a novel genus, for which the name Cnuella takakiae gen. nov., sp. nov. is proposed. The type strain is RG1-1(T) ( = CGMCC 1.12492(T) = DSM 26897(T)).

[Surveillance of schistosomiasis in national surveillance sites of Fuqing City and Xiapu County, 2006 -2009].

OBJECTIVE: To understand the status of national surveillance sites of schistosomiasis in Fuqing City and Xiapu County. METHODS: According to the National Scheme of Shistosomiasis Surveillance, the data of the surveillance and field survey in the national surveillance sites of schistosomiasis of Fuqing City and Xiapu County were collected and analyzed statistically from 2006 to 2009. RESULTS: Twenty residual Oncomelania snail points and 8 villages with snails were found in 36 surveillance sites. The snail areas were 35 900 m2. Serological examinations were conducted in 3 109 residents, and 17 persons were positive, 280 mobile persons from schistosomiasis endemic areas were examined serologically, and 10 persons were positive, among whom 2 had eggs and miracidia in their stools. A total of 122 appendix samples were examined, and no schistosome eggs were found. Totally 527 head of farm cattle in the region with snails were examined by stool tests, and no schistosome eggs were found. CONCLUSION: The areas of residual snails are large and wide spread, and the imported patients are found frequently, so the long-term surveillance and control are necessary.

Functional identification of cytokinesis-related genes from tobacco BY-2 cells.

The molecular mechanisms controlling cytokinesis in plant cell division cycle remains largely unknown. In this study, a functional approach was taken to identify genes that may play roles in cytokinesis in tobacco BY-2 cells, using fission yeast as the host organism. A total of 22 BY-2 genes that perturbed the terminal stage of cell division when ectopically expressed in yeast cells were isolated, among which, several encode for uncharacterized genes. Additionally, RT-PCR analysis indicated that four of the isolated genes were expressed in a cell cycle-dependent manner. Our results demonstrate that fission yeast system can be efficiently used to identify the genes that may function, either positively or negatively, in the regulation of cytokinesis. More importantly, the candidate genes we have isolated in this work can provide useful information for unraveling the regulators controlling cell separation at the late stage of BY-2 cell division.

Functional characterization of Gossypium hirsutum profilin 1 gene (GhPFN1) in tobacco suspension cells. Characterization of in vivo functions of a cotton profilin gene.

Cotton fiber is an extremely long plant cell. Fiber elongation is a complex process and the genes that are crucial for elongation are largely unknown. We previously cloned a cDNA encoding an isoform of cotton profilin and found that the gene (designated GhPFN1) was preferentially expressed in cotton fibers. In the present study, we have further analyzed the expression pattern of GhPFN1 during fiber development and studied its cellular function using tobacco suspension cells as an experimental system. We report that expression of GhPFN1 is tightly associated with fast elongation of cotton fibers whose growth requires an intact actin cytoskeleton. Overexpression of GhPFN1 in the transgenic tobacco cells was correlated with the formation of elongated cells that contained thicker and longer microfilament cables. Quantitative analyses revealed a 2.5-3.6 fold increase in total profilin levels and a 1.6-2.6 fold increase in the F-actin levels in six independent transgenic lines. In addition to the effect on cell elongation, we also observed delayed cell cycle progression and a slightly lower mitotic index in the transgenic cells. Based on these data, we propose that GhPFN1 may play a critical role in the rapid elongation of cotton fibers by promoting actin polymerization.

[The role of cortical microtubules in moss protonemal cells during dehydration/rehydration cycle].

Plant cells response to water deficit through a variety of physiological processes. In this work, we studied the function of microtubule cytoskeleton during dehydration/rehydration cycle in moss (Atrichum undulatum) protonemal cells as a model system. The morphological and cytological change of protonemal cells during dehydration and rehydration cycle were first investigated. Under normal conditions, protonemal cells showed bright green colour and appeared wet and fresh. Numerous chloroplasts distributed regularly throughout the cytoplasm in each cell. After dehydration treatment, protonemal cells lost most of their chlorophylls and turned to look yellow and dry. In addition, dehydration caused plasmolysis in these cells. Upon rehydration, the cells could recover completely from the dehydrated state. These results indicated that moss had a remarkable intrinsic ability to survive from the extreme drought stress. Microtubule, an important component of cytoskeleton, is considered to play crucial roles in the responses to some environmental stresses such as cold and light. To see if it is also involved in the drought tolerance, dynamic organization of microtubules in protonemal cells of Atrichum undulatum subjected to drought and rehydration were examined by indirect immunofluorescence combined with confocal lasersharp scanning microscopy. The cortical microtubules were arranged into a fine structure with a predominant orientation parallel to the long axis of the cells in the control cells. After dehydration, the microtubule organization was remarkablly altered and the fine microtubule structure disappeared whereas some thicker cables formed. When the cells were grown under rehydration conditions, the fine microtubule arrays reappeared. These results provided a piece of evidence that microtubules play a role in the cellular responses to drought stress in moss. Furthermore, we analyzed the effects of the microtubule-disrupting agent colchicine on the morphology recovery of the protonemal cells during rehydration process. The cells were incubated with colchicine, followed by drought stress treatment and rehydration in the presence of colchicine to prevent recovery of microtubule organization. Results from immunofluorescence showed that microtubule arrays were broken down into smaller fragments. Compared to the cells treated with drought stress alone, the cells treated with drought stress in the presence of colchicine could not recover after rehydration treatment. The morphology resembled those of the drought treated cells, with obvious plasmolysis phenomena and loss of chlorophyll content. These results support the notion that microtubules were involved in the deccication tolerance mechanism in Atrichum undulatum.