Human health impact due to arsenic contaminated rice and vegetables consumption in naturally arsenic endemic regions.

Rice and vegetables cultivated in naturally arsenic (As) endemic areas are the substantial source of As body loading for persons using safe drinking water. However, tracing As intake, particularly from rice and vegetables by biomarker analysis, has been poorly addressed. This field investigation was conducted to trace the As transfer pathway and measure health risk associated with consuming As enriched rice and vegetables. Purposively selected 100 farmers from five sub-districts of Chandpur, Bangladesh fulfilling specific requirements constituted the subjects of this study. A total of 100 Irrigation water, soils, rice, and vegetable samples were collected from those farmers' who donated scalp hair. Socio-demographic and food consumption data were collected face to face through questionnaire administration. The mean As level in irrigation water, soils, rice, vegetables, and scalp hairs exceeded the acceptable limit, while As content was significant at 0.1%, 5%, 0.1%, 1%, and 0.1% probability levels, respectively, in all five locations. Arsenic in scalp hair is significantly (p ≤ 0.01) correlated with that in rice and vegetables. The bioconcentration factor (BCF) for rice and vegetables is less than one and significant at a 1% probability level. The average daily intake (ADI) is higher than the RfD limit for As. Both grains and vegetables have an HQ (hazard quotient) > 1. Maximum incremental lifetime cancer risk (ILCR) showed 2.8 per 100 people and 1.6 per 1000 people are at considerable and threshold risk, respectively. However, proteinaceous and nutritious food consumption might have kept the participants asymptomatic. The PCA analysis showed that the first principle component (PC1) explains 91.1% of the total variance dominated by As in irrigation water, grain, and vegetables. The dendrogram shows greater variations in similarity in rice and vegetables As, while the latter has been found to contribute more to human body loading compared to grain As.

Mechanical performance of graphenex/poly(ether ketone ketone) composite sheets by hot pressing.

Polymer composites are gradually replacing traditional metal materials in the fields of aviation, aerospace, automotive and medicine due to their corrosion resistance, light weight and high strength. Moulding technology and organization morphology of polymer composite are key elements affecting the quality of products and their application, so a vacuum hot pressing process for graphenex/poly(ether ketone ketone) (PEKK) (x = 0%, 2%, 3%, 4%, 5%, 6%) composite powders is explored with particularly designed moulding parameters to achieve high conductive properties and good mechanical properties in graphene/PEKK composite sheet with thickness of 1.25 mm and diameter of 80 mm. The vacuum environment ensures that the graphene is not oxidized by air during hot pressing molding, which is essential for achieving conductive property in the graphene/PEKK composite; The hot pressing temperature of each graphene/PEKK composite powder is higher than glass transition temperature but lower than melting temperature, which ensures the graphene/PEKK composite powders is fully compacted and then graphene is fully lapped in the composite sheet. In addition, the graphene/PEKK composite sheet shows conductive property when the graphene content increases to 3wt%, and then the conductivity of the composites increases and then decreases with a peak value at 5wt% with increasing graphene content. By comparing the mechanical properties and microstructure morphology of the graphene/PEKK composite sheets, it was obtained that graphene content has an obvious effect on the mechanical properties of the composites, e.g., the mechanical properties will be increased as the graphene content increasing when graphene content is more than 3%. The graphene distribution law of the composite material with different graphene contents is analysed using a scanning electron microscope (SEM).

Clinical significance of CA 19.9 and LINC01197 in pancreatic cancer.

OBJECTIVE: This study aimed to explore the expression and clinical significance of LINC01197 in serum of patients with pancreatic cancer (PC). PATIENTS AND METHODS: Fifty PC patients (patient group) treated in our hospital from March 2012 to April 2014 were collected, and another 50 normal people (normal group) were collected for physical examination. The LINC01197 expression in serum of the two groups was detected by qRT-PCR method, and the CA 19.9 expression in serum was detected by Roche automatic biochemistry. The expression and diagnostic value of CA 19.9 and LINC01197 in PC were analyzed, and the relationship between LINC01197 and prognosis of PC patients was observed. RESULTS: The CA 19.9 expression in the patient group was significantly higher than that in the normal group (p<0.001). Their area under the curve was 0.791 and 0.944 respectively. The incidence of phases III+IV, lymphatic invasion, and distant metastasis in patients with low expression of LINC01197 is significantly higher than that in those with high expression, and has higher diagnostic value. With the progress of clinical staging, the TNM expression decreased gradually and there were differences between groups (p<0.001). Spearman's test analysis found that the decreased TNM staging of LINC01197 increased gradually (r=-0.816, p<0.001), and the area under the curve of LINC01197 distinguishing phase I and phase II+phase+III+phase IV was 0.930. The 1-year survival rate and 5-year survival rate of patients in low expression group were lower than those in high expression group (p1 year =0.037, p5 year =0.014). Distant metastasis is an independent prognostic factor for PC patients to survive for 1 to 5 years. Differentiation, TNM staging, and LINC01197 are independent prognostic factors for PC patients to survive for 5 years. CONCLUSIONS: The low expression of LINC01197 in PC patients indicates poor prognosis of patients and is expected to be a potential diagnostic and prognostic indicator of PC.

[Intervention study of compassion fatigue of oncology nurses in Balint group activities].

Objective: To explore the effectiveness of Balint group on compassion fatigue among oncology nurses. Methods: From January to December 2016, 35 oncology nurses from one general hospital were enrolled. 18 cases were allocated in the observation group and 17 cases in the control group by computer randomization. Nurses in the observation group were received a total of 8 times Balint Group activities, with 2 times a month and 1.5 hours each time, which is aiming to discuss difficult cases encountered in the clinic to help nurses have a deeper experience and a better understanding of the emotions and behaviors, fantasies and needs between nurse-patient interaction. Nurses in the control group without intervention. All the Participants were requested to complete the survey of the Professional Quality of Life (ProQOL) , the Jefferson Scale of Empathy-Health Professionals (JSE-HP) , and the General Health Questionnaire (GHQ) at pre and post intervention. Results: Before intervention, two group of nurses in age, working years, marriage, and education were not statistically significant (P>0.05). There was no difference in the scores of empathy, compassion satisfaction, secondary traumatic stress, and General health (P>0.05). After intervention, the scores of JSE-HP and its three dimensions of perspective taking, emotional care, and trans-positional consideration in the observation group had significantly higher than the control group (P<0.05). The level of compassion satisfaction in the observation group was higher, and the general health status was lower (P<0.05). There was no statistically difference in the level of burnout and secondary traumatic stress between two groups (P>0.05) . Conclusion: Balint group has a positive role in promoting nurses'empathetic skills, compassion satisfaction and mental health.

Accumulation of mercury and cadmium in rice from paddy soil near a mercury mine.

Paddy soil and rice (Oryza sativa L.) in the Wanshan mining area in Guizhou Province, China, have been contaminated by toxic trace metals such as cadmium (Cd) and mercury (Hg). The present study examined correlations between the types and physicochemical parameters of the soil and the contents of trace metals and the different forms of Hg in rice. The health risks of consuming contaminated rice from the Wanshan mining area were also assessed. Sequential extraction procedures were used to investigate the chemical behavior of Hg in the soil. The results showed that Hg and Cd were the most abundant trace metals in the Wanshan mining area. The toxic methylmercury (MeHg) content was substantial in brown rice, and the total amounts of total Hg (THg), diethylenetriaminepentaacetic acid-Hg, and water-soluble Hg varied in the rhizosphere and non-rhizosphere soils. An antagonistic interaction between Mn in brown rice, straw, and husk and MeHg in brown rice was also shown. An analysis of calculated dietary intake, target hazard quotients, and hazard indexes showed a potential risk of transferring Hg, MeHg, and Cd to humans when rice from the Wanshan mining area is consumed. Therefore, it must be concluded that consuming contaminated rice near the Wanshan mining area is a potential threat to human health.

Cadmium accumulation in and tolerance of rice (Oryza sativa L.) varieties with different rates of radial oxygen loss.

Cadmium (Cd) uptake and tolerance were investigated among 20 rice cultivars based on a field experiment (1.2 mg Cd kg⁻¹ in soil) and a soil pot trial (control, 100 mg Cd kg⁻¹), and rates of radial oxygen loss (ROL) were measured under a deoxygenated solution. Significant differences were found among the cultivars in: (1) brown rice Cd concentrations (0.11-0.29 mg kg⁻¹) in a field soil, (2) grain Cd tolerance (34-113%) and concentrations (2.1-6.5 mg kg⁻¹) in a pot trial, and (3) rates of ROL (15-31 mmol O2 kg⁻¹ root d.w. h⁻¹). Target hazard quotients were calculated for the field experiment to assess potential Cd risk. Significant negative relationships were found between rates of ROL and concentrations of Cd in brown rice or straw under field and greenhouse conditions, indicating that rice cultivars with higher rates of ROL had higher capacities for limiting the transfer of Cd to rice and straw.

Cadmium tolerance and accumulation in cultivars of a high-biomass tropical tree (Averrhoa carambola) and its potential for phytoextraction.

Averrhoa carambola is a high-biomass tropical tree that has been identified as a Cd accumulator. In the present study, field survey, pot, and hydroponic experiments were conducted to investigate the variation of Cd tolerance and accumulation in cultivars of A. carambola as well as its potential for phytoextraction. In the field survey, it was found that concentrations of Cd in aerial tissues of A. carambola varied greatly among sites and cultivars. The Cd bioconcentration factors (BCFs) and Cd removals by the field-grown A. carambola differed significantly among sites but not among cultivars. Nonetheless, all four carambola cultivars investigated were able to accumulate considerably high concentrations of Cd in their shoots, which indicated that the 4-yr-old carambola stands could remove 0.3 to 51.8% of the total Cd content in the top 20-cm soil layer. When cultured in Cd-spiked soils, the carambola cultivar Hua-Di always showed higher Cd tolerance than the other cultivars; however, this tendency was not confirmed by hydroponic experiment. The Cd BCFs of cultivar Thailand grown in soils with 6 and 12 mg Cd kg(-1) were highest among cultivars, whereas this trend was reversed at 120 mg Cd kg(-1) treatment. Nevertheless, the pot- and hydroponics-grown carambola cultivars generally showed higher capacities to tolerate and accumulate Cd, compared with the control species. The present results indicate that a strong ability to tolerate and accumulate Cd seems to be a trait at the species level in A. carambola, although some degree of variances in both Cd tolerance and accumulation exists among cultivars.

Vegetation changes and partitioning of selenium in 4-year-old constructed wetlands treating agricultural drainage.

The knowledge of selenium (Se) partitioning in treatment wetlands and wetland vegetation management are essential for long-term effective operation of constructed wetlands treating Se-laden agricultural tile-drainage in central California. In this field study, samples from different compartments of treatment wetlands were collected and the vegetation change in each wetland cell was examined four years after the wetland's inception. The results showed that saltgrass (Distichlis spicata) and rabbitfoot grass (Polypogon monspeliensis) were less competitive than cattail (Typha latifolia) and saltmarsh bulrush (Scirpus robustus). Over 90% of the wetland cell originally vegetated with saltgrass or rabbitfoot grass was occupied by invasive plants--i.e., when invasive species were not controlled in the wetlands. More Se was likely found in sediments from vegetated regions, compared to the unvegetated areas of the wetland cell. Particularly, rhizosphere sediments accumulated about 4-fold more Se than non-rhizosphere sediments. Among the total Se retained in the wetland 90% of the total Se was partitioned in the top 10-cm layer of sediment. The Se accumulation in plant materials accounted for about 2% of the total Se mass retained in each wetland cell. This field study demonstrated that wetland plants play significant roles in the treatment of Se-laden agricultural drainage.

Zinc and cadmium accumulation and tolerance in populations of Sedum alfredii.

To investigate the variation of Zn and Cd accumulation and tolerance of Sedum alfredii (a newly reported Zn/Cd hyperaccumulator), field surveys and hydroponic experiments were conducted among three populations of this species: two originating from old Pb/Zn mines in Zhejiang (ZJ) and Hunan (HN) Provinces and one from a "clean" site in Guangdong (GD) Province, China. Under field conditions, up to 12,524 and 12,253 mg kg(-1) Zn, and 1400 and 97 mg kg(-1) Cd in shoots of ZJ and HN plants were recorded respectively. Under hydroponic conditions, ZJ and HN plants accumulated significantly higher Zn and Cd in their leaves and stems, and possessed significantly higher Zn and Cd tolerance than GD plants. Among the two contaminated populations, ZJ plants showed higher Cd tolerance and accumulation (in leaves) than HN plants. The present results indicate that significant differences in Zn and Cd accumulation and tolerance exist in populations of S. alfredii.

Increase of glutathione in mine population of Sedum alfredii: a Zn hyperaccumulator and Pb accumulator.

Phytochelatins (PCs) have been induced in a large range of plant species, but their role in heavy metal tolerance is unclear. Sedum alfredii is a new zinc (Zn) hyperaccumulator and lead (Pb) accumulator found in an old Pb/Zn mine in the Zhejiang Province of China. Until now, the mechanisms of its hyperaccumulation/accumulation and tolerance were poorly understood. The aim of this work was to investigate whether PCs were differentially produced in mine populations of S. alfredii compared with a non-mine control of the same species. The results showed that plants from the mine site were more tolerant to increasing Zn and Pb concentrations than those from the control site. No PCs and cysteine (Cys) were detected by pre-column derivatization with HPLC fluorescence in any tissues of two populations at any treatment, which in turn indicated they were not responsible for Zn and Pb tolerance in the mine population. Instead, Zn and Pb treatments resulted in the increase of glutathione (GSH) for both populations in a tissue-dependent manner. Significant increases were observed in leaf, stem and root tissues of plants grown on the mine site. The results suggest that GSH, rather man PCs, may be involved in Zn and Pb transport, hyperaccumulation/accumulation and tolerance in mine population of S. alfredii.

Accumulation of lead, zinc, copper and cadmium by 12 wetland plant species thriving in metal-contaminated sites in China.

The concentrations of lead, zinc, copper and cadmium accumulated by 12 emergent-rooted wetland plant species including different populations of Leersia hexandra, Juncus effusus and Equisetum ramosisti were investigated in field conditions of China. The results showed that metal accumulation by wetland plants differed among species, populations and tissues. Populations grown in substrata with elevated metals contained significantly higher metals in plants. Metals accumulated by wetland plants were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them. That some species/populations could accumulate relatively high metal concentrations (far above the toxic concentration to plants) in their shoots indicates that internal detoxification metal tolerance mechanism(s) are also included. The factors affecting metal accumulation by wetland plants include metal concentrations, pH, and nutrient status in substrata. Mostly concentrations of Pb and Cu in both aboveground and underground tissues of the plants were significantly positively related to their total and/or DTPA-extractable fractions in substrata while negatively to soil N and P, respectively. The potential use of these wetland plants in phytoremediation is also discussed.

Removal and distribution of iron, manganese, cobalt, and nickel within a Pennsylvania constructed wetland treating coal combustion by-product leachate.

A flow-through wetland treatment system was constructed to treat coal combustion by-product leachate from an electrical power station at Springdale, Pennsylvania. In a nine-compartment treatment system, four cattail (Typha latifolia L.) wetland cells (designated Cells 1 through 4) successfully removed iron (Fe) and manganese (Mn) from the inlet water; Fe and Mn concentrations were decreased by an average of 91% in the first year (May 1996-May 1997), and by 94 and 98% in the second year (July 1997-June 1998), respectively. Cobalt (Co) and nickel (Ni) were decreased by an average of 39 and 47% in the first year, and 98 and 63% in the second year, respectively. Most of the metal removed by the wetland cells was accumulated in sediments, which constituted the largest sink. Except for Fe, metal concentrations in the sediments tended to be greater in the top 5 cm of sediment than in the 5- to 10- or 10- to 15-cm layers, and in Cell 1 than in Cells 2, 3, and 4. Plants constituted a much smaller sink for metals; only 0.91, 4.18, 0.19, and 0.38% of the Fe, Mn, Co, and Ni were accumulated annually in the aboveground tissues of cattail, respectively. A greater proportion of each metal (except Mn) was accumulated in cattail fallen litter and submerged Chara (a macroalga) tissues, that is, 2.81, 2.75, and 1.05% for Fe, Co, and Ni, respectively. Considerably higher concentrations of metals were associated with cattail roots than shoots, although Mn was a notable exception.

Distribution characteristics of fluoride and aluminum in soil profiles of an abandoned tea plantation and their uptake by six woody species.

Distribution characteristics of fluoride (F) and aluminum (Al) in soil profiles of an abandoned tea plantation in Hong Kong and their uptake by six woody species namely Camellia sinensis, Melastoma affine, Sterculia lanceolata, Ardisia crenata, Acacia formosa and Machilus thunbergii were investigated. C. sinensis accumulated both F (656 mg/kg in the leaves) and Al (8910 mg/kg in the leaves). M. Affine only accumulated Al (9932 mg/kg in the leaves), while S. lanceolata, A. crenata, A. formosa and M. Thunbergii were Al (26-115 mg/kg in the leaves) and F (20-25 mg/kg in the leaves) excluders. Water-soluble F and Al contents accumulated in surface soils (especially 0-3 cm) and decreased with depth along soil profiles: A layers (2.0 +/- 0.6 and 31 +/- 5.8 mg/kg) > B layers (1.5 +/- 0.2 and 27 +/- 3.5 mg/kg) > C layers (1.3 +/- 0.2 and 20 +/- 2.7 mg/kg), respectively. The water-soluble, NH4Ac-extractable and HCl-extractable F in soil profiles were significantly correlated (P < .01). F concentrations in all soil layers (n = 51) of soil profiles (n = 17) were significantly correlated (P < .01) to Al concentrations in terms of water-soluble Al/F, HCl-extractable Al/F and NH4Ac-extractable Al/F, due to the formation of Al-F complexes in soil. F contents extracted with deionized water (pH = 6.68), 1 mol/l HCl and 1 mol/l NH4Ac in soil could be used to predict F concentrations in the leaves, stems and roots of the six plants.

A katanin-like protein regulates normal cell wall biosynthesis and cell elongation.

Fibers are one of the mechanical tissues that provide structural support to the plant body. To understand how the normal mechanical strength of fibers is regulated, we isolated an Arabidopsis fragile fiber (fra2) mutant defective in the mechanical strength of interfascicular fibers in the inflorescence stems. Anatomical and chemical analyses showed that the fra2 mutation caused a reduction in fiber cell length and wall thickness, a decrease in cellulose and hemicellulose contents, and an increase in lignin condensation, indicating that the fragile fiber phenotype of fra2 is a result of alterations in fiber cell elongation and cell wall biosynthesis. In addition to the effects on fibers, the fra2 mutation resulted in a remarkable reduction in cell length and an increase in cell width in all organs, which led to a global alteration in plant morphology. The FRA2 gene was shown to encode a protein with high similarity to katanin (hence FRA2 was renamed AtKTN1), a protein shown to be involved in regulating microtubule disassembly by severing microtubules. Consistent with the putative function of AtKTN1 as a microtubule-severing protein, immunolocalization demonstrated that the fra2 mutation caused delays in the disappearance of perinuclear microtubule array and in the establishment of transverse cortical microtubule array in interphase and elongating cells. Together, these results suggest that AtKTN1, a katanin-like protein, is essential not only for normal cell wall biosynthesis and cell elongation in fiber cells but also for cell expansion in all organs.

Essential role of caffeoyl coenzyme A O-methyltransferase in lignin biosynthesis in woody poplar plants.

Caffeoyl coenzyme A O-methyltransferase (CCoAOMT) has recently been shown to participate in lignin biosynthesis in herbacious tobacco plants. Here, we demonstrate that CCoAOMT is essential in lignin biosynthesis in woody poplar (Populus tremula x Populus alba) plants. In poplar stems, CCoAOMT was found to be expressed in all lignifying cells including vessel elements and fibers as well as in xylem ray parenchyma cells. Repression of CCoAOMT expression by the antisense approach in transgenic poplar plants caused a significant decrease in total lignin content as detected by both Klason lignin assay and Fourier-transform infrared spectroscopy. The reduction in lignin content was the result of a decrease in both guaiacyl and syringyl lignins as determined by in-source pyrolysis mass spectrometry. Fourier-transform infrared spectroscopy indicated that the reduction in lignin content resulted in a less condensed and less cross-linked lignin structure in wood. Repression of CCoAOMT expression also led to coloration of wood and an elevation of wall-bound p-hydroxybenzoic acid. Taken together, these results indicate that CCoAOMT plays a dominant role in the methylation of the 3-hydroxyl group of caffeoyl CoA, and the CCoAOMT-mediated methylation reaction is essential to channel substrates for 5-methoxylation of hydroxycinnamates. They also suggest that antisense repression of CCoAOMT is an efficient means for genetic engineering of trees with low lignin content.

Zinc, lead and cadmium tolerance, uptake and accumulation by Typha latifolia.

Zinc, lead and cadmium tolerance in four populations of Typha latifolia raised from seed collected from metal-contaminated and uncontaminated sites were investigated. Metal concentrations in natural plant populations showed that Zn, Pb and Cd in the leaves were maintained at low levels (Zn: 22-122, Pb: 4.7-40 and Cd: 0.2-0.8 µg g-1 d. wt), although concentrations of these metals in the associated soil-sediments (total concentrations of Zn: 86-3009, Pb: 26-18894 and Cd: 1.4-26 µg-1 d. wt) and in the roots (Zn: 46-946, Pb: 25-3628 and Cd: 1.0-17 µg g-1 d. wt) varied widely. Some differences were found between metal-contaminated and uncontaminated populations in terms of metal uptake under controlled conditions. Seedlings from metal-contaminated populations accumulated considerably more metals (up to nearly twice as much Zn and Pb and three times as much Cd) in roots than the uncontaminated population in a pot trial. In general, however, different populations of T. latifolia showed similar growth responses (the longest leaf elongation, the longest root elongation, shoot and root d. wt), metal uptake and indices of metal tolerance when seedlings were grown in the same metal treatment solutions or in the same metal-contaminated media under laboratory conditions. The data do not support the hypothesis that populations from metal-contaminated sites have evolved tolerance to Zn, Pb and Cd, but rather that T. latifolia shows constitutional tolerance.

Copper and nickel uptake, accumulation and tolerance in Typha latifolia with and without iron plaque on the root surface.

The effects of iron plaque on the growth of Typha latifolia L. and accumulation of copper and nickel in T. latifolia were investigated under laboratory conditions in nutrient solution cultures. Seedlings with and without iron plaque on their roots were exposed to 0.05 µg ml-1 Cu and 0.10 µg ml-1 Ni solutions for 72 d. The results showed no differences in root and shoot d. wt and leaf elongation when Cu or Ni were added to the solution and in the presence or absence of plaque. However, root length was reduced by Cu and Ni, and the reduction in root length was greater in the presence of plaque. Some Cu and Ni was adsorbed on root surfaces; roots with plaque took up more Cu, but less Ni than those without. The presence of plaque did not alter Cu uptake and translocation but increased Ni uptake and translocation. Most of the Cu and Ni taken up was retained in the roots, suggesting that the root tissue rather than the root surface or plaque is the main barrier for Cu and Ni transport. The results differ from those reported for other species.

Association of caffeoyl coenzyme A 3-O-methyltransferase expression with lignifying tissues in several dicot plants.

Caffeoyl coenzyme A 3-O-methyltransferase (CCoAOMT) was previously shown to be associated with lignification in both in vitro tracheary elements (TEs) and organs of zinnia (Zinnia elegans). However, it is not known whether this is a general pattern in dicot plants. To address this question, polyclonal antibodies against zinnia recombinant CCoAOMT fusion protein were raiseed and used for immunolocalization in several dicot plants. The antibodies predominantly recognized a protein band with a molecular mass of 28 kD on western analysis of tissue extracts from zinnia, forsythia (Forsythia suspensa), tobacco (Nicotiana tabacum), alfalfa (Medicago sativa), and soybean (Glycine max). Western analyses showed that the accumulation of CCoAOMT protein was closely correlated with lignification in in vitro TEs of zinnia. Immunolocalization results showed that CCoAOMT was localized in developing TEs of young zinnia stems and in TEs, xylem fibers, and phloem fibers of old stems. CCoAOMT was also found to be specifically associated with all lignifying tissues, including TEs, xylem fibers, and phloem fibers in stems of forsythia, tobacco, alfalfa, soybean, and tomato (Lycopersicon esculentum). The presence of CCoAOMT was evident in xylem ray parenchyma cells of forsythia, tobacco, and tomato. In forsythia and alfalfa, pith parenchyma cells next to the vascular cylinder were lignified. Accordingly, marked accumulation of CCoAOMT in these cells was observed. Taken together, these results showed a close association of CCoAOMT expression with lignification in dicot plants. This supports the hypothesis that the CCoAOMT-mediated methylation branch is a general one in lignin biosynthesis during normal growth and development in dicot plants.

Induction of cysteine and serine proteases during xylogenesis in Zinnia elegans.

The terminal process of xylogenesis, autolysis, is essential for the formulation of a tubular system for conduction of water and solutes throughout the whole plant. Several hydrolase types are implicated in autolysis responsible for the breakdown of cytoplasm. Here, we characterize p48h-17 cDNA from in vitro tracheary elements (TEs) of Zinnia elegans which encodes a preproprotein similar to papain. The putative mature protein, a cysteine protease, has a molecular mass of 22,699 Da with a pI of 5.7. DNA gel blot analysis indicated that p48h-17 is likely encoded by one or two genes. The p48h-17 mRNA accumulated markedly in in vitro differentiating TEs, whereas it appeared not to be induced in response to senescence and wounding in the leaves or H2O2 challenge in the cultured mesophyll cells. In stems, the expression of the p48h-17 gene was preferentially associated with differentiating xylem. Activity gel assays demonstrated that a cysteine and a serine protease, which had apparent molecular masses of 20 kDa and 60 kDa, respectively, were markedly induced during in vitro TE differentiation. The cysteine protease activity was also preferentially present in the xylem of Zinnia stems. Transient expression of the p48h-17 cDNA in tobacco protoplasts resulted in the production of a 20 kDa cysteine protease. Taken together, the results indicate that the p48h-17 gene appears to be preferentially associated with xylogenesis, and both the cysteine and serine proteases might be involved in autolysis during xylogenesis.