Plant mitogen-activated protein kinases (MAPKs) are involved in growth, development and responses to endogenous and environmental cues, which link stimuli that are activated by external sensors to cellular responses. In Arabidopsis, as a model, all of MAP kinase genes have been listed and classified. Based on the Arabidopsis MAPK families, a number of MAP kinase genes in other plant species have been recently isolated and classified. Most of the cloned MAPK genes can be activated by a variety of stress stimuli including pathogen infection, wounding, temperature, drought, salinity, osmolarity, UV irradiation, ozone and reactive oxygen species. Some tools and strategies are used to investigate their functions and signal pathways under different environmental stress, indicating complexity and crosstalk of plant MAP kinase signaling pathways. It is still necessary to explore more novel tools and strategies to clarify MAPK signaling pathways, and how to apply the MAPK cascade to improve the resistance of crop to abiotic and biotic stress.
The degradation of Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco, EC 184.108.40.206) in wheat (Triticum aestivum L. cv. Yangmai 158) leaves during dark-induced senescence was studied. An in vivo degradation product of Rubisco large subunit (LSU) with molecular weight of 50 kD was detected by SDS-PAGE and immunoblotting with antibody against tobacco Rubisco. This fragment could also be detected in natural senescence. The result also suggested that the Rubisco holoenzyme had not dissociated when LSU hydrolyzed from 53 kD to 50 kD. And LSU could be fragmented to 50 kD at 30-35 ℃ and at pH 7.5 in crude enzyme extracts of wheat leaves dark-induced for 48 h, which suggested that maybe LSU was degraded to 50 kD by an unknown protease in chloroplast.
A full-length cDNA (LlpCel1) encoding an endo-1,4-β-glucanase (EGase) was isolated from pollen tubes of Lilium longiflorum Thunb. by RT-PCR and RACE. The deduced protein, which is predicted to be a compact globular protein, is of 490 amino acids, including a putative 21 amino acid-signal peptide. LlpCel1 shares high level of homology (about 50%) with plant secreted EGases, which bear apparently neither trans-membrane domain, nor cellulose-binding domain (CBD). LlpCel1 belongs to glycosyl hydrolase family 9. LlpCel1 transcripts were detected in pollen grains, germinating pollen and elongating pollen tubes with a similar level, whereas LlpCel1 transcripts were not detectable in all other lily tissues examined. The specific expression pattern suggests that LlpCel1 is confined to lily pollen germination and pollen tube elongation.
The 1 216 bp 5'' upstream r-egion of the gene encoding the class ⒒ chitinase VCH3 was isolated from grapevine (Vitis amurensis Rubr.) (Genbank accession number AF441123) and two inverse salicylic acid (SA) responsive cis -acting motifs (TGACG) were found at -1 181 bp and -293 bp upstream of the transcriptional start site, respectively. To characterize the VCH3 promoter, four chimeric constructs varied in the length of promoter fragments from -1 187 bp, -892 bp, -589 bp and -276 bp to +7 bp relative to the transcriptional start site were placed to the upstream of the 円-glucuronidase (GUS) coding region and transferred to Nicotiana tobacum L. cv. NC89 by Agrobacterium tumefaciens-mediated leaf discs transformation. The functional properties of each promoter fragment were examined by fluorometric and histochemical analysis of GUS activity in the transgenic tobacco root treated with SA. The VCH3 (-276) GUS construct, containing only the TATA and CAAT boxes was shown to have little inducibility upon treatment with SA. However, the similarly higher level of GUS expression was observed in the VCH3 (-589) GUS or VCH3 (-892) GUS transgenic plants with only one cis -acting motif, while the most abundance of GUS expression was found in the full-length promoter (-1187 bp to +7 bp) with two cis -acting motifs. These results indicated that the two cis -acting motifs were required for the maximal expression of the GUS reporter gene by SA induction. In addition, the histochemical analysis of GUS activity showed that the four VCH3 promoter fragments were more active in vascular tissue than that in outer and inner cortexes of the transgenic tobacco roots treated by SA, suggesting that the region involved in vascular tissue-specific expression of VCH3 promoter upon SA inducibility appears to be located between positions -276 bp and +7 bp relative to the transcriptional start site. In general, these results indicate a potential use for the SA induction of VCH3 promoter in genetic engineering.
Somatic embryogenesis was successfully induced with auxin in high concentration from immature cotyledons of eighteen varieties of soybean (Glycine max (L.) Merr.) adaptable for planting in Northeast China. The frequency of somatic embryogenesis varied from 0.29% to 77.62% among eighteen genotypes of soybean. The proliferative somatic embryos were gained from ten varieties of soybean at rate of 5.2%-22.1%. For the first time, plantlets were obtained even after subcultured and maintained on solid medium for over one year. This system provided a new and efficient receptor for genetic transformation of soybean.
Two novel bis-labdanic diterpenoids named calcaratarin G and calcaratarin H were isolated from the rhizomes of Alpinia calcarata Rosc. Their structures were elucidated to be a pair of stereoisomers on the basis of the spectral evidence. The 2D NMR techniques including 1H-1H COSY, HMQC, HMBC, NOESY and HRFABMS were extensively applied to establish the structures.
Random amplified polymorphic DNA (RAPD) method was applied to assess genetic variation and population structure of Thalictrum petaloideum L. (Ranunculaceae). Two hundred and forty-six individuals from 11 populations of the species were investigated by RAPD profiles. Twenty selected RAPD primers generated 125 bands, in which 120 were polymorphic. The results revealed a high level of genetic variation (percentage of polymorphic bands (PPB) was 96%, Nei’s gene diversity (h) was 0.350 2 and shannon’s information index (I ) was 0.519 9 at the species level). The differentiation among the populations was high (GST = 0.351 1) in this species. Result of analyzing of molecular variance (AMOVA) showed that 38.88% of genetic variance was found among the populations. Positive correlation with r = 0.194 5 (P = 0.000 2) was found between genetic distance and geographic distance among populations. Two populations distributed in the drainage basin of Yangtz River affined genetically and formed one clade and the rest nine populations formed the other clade in both unweighted pair-group method using arithmetic average (UPGMA) trees made by two different methods. It was very clear that these two populations were very special, and must be closely related in history, despite the fact that they now share quite weak link to the rest populations through gene communication.
The molecular phylogenetics of sect. Parrya Myre of Pinus L. was analyzed based on chloroplast matK gene sequence data. The section was resolved as paraphyletic because members of the sect. Strobus were nested within a clade composed by the Asian members of the section, including the Vietnamese P. krempfii Lecomte, which was strongly supported with a bootstrap value of 92%. In this topology, the three sampled species of sect. Strobus formed a strongly supported monophyletic group, while their relationships of Asian species of sect. Parrya were not clear. P. krempfii was grouped with P. gerardiana Wall. ex D. Don with low bootstrap support. The relationships among the Asian members of the sect. Parrya, i.e. P. bungeana Zucc. ex Loud., P. gerardiana and the recently described endangered pine, P. squamata X. W. Li, was not resolved, although the monophyly of the three pines was strongly supported in the combined analysis of four cpDNA sequences. The topology of the neighbor joining tree revealed an assemblage of the American members of the section, which also appeared in the majority rule tree with weak bootstrap support. However, this assemblage was not resolved in the consensus tree of the parsimonious analysis. The American subsect. Balfourianae Engelm. formed a weakly supported group including P. aristata Engelm., while the relationships among and within the other two American subsections, Cembroides Englem. and Rzedowskianae Carv., were not resolved, as the members of them formed a polytomy in the consensus tree of the parsimonious analysis. The biogeographical implications of the results are also discussed in this paper.
Abundant well-preserved animal and macroalgal fossils were discovered in the Early-Middle Cambrian Kaili Formation of Taijiang County, Guizhou Province, China, which constitute the Kaili Biota, named as one of the three important Burgess Shale-type faunas. The bryophyte-like fossil (Parafunaria sinensis Yang gen. et sp. nov) was discovered in the horizon of occurrence of Macroalgal fossils. The fossil of P. sinensis possesses typical characters of bryophyte, such as whorled leaves, capsule and seta, and complex rhizoid or foot. We infer that the bryophyte-like fossil could be the ancestor of bryophyte. The discovery provides a new lead for further study on the origin and evolution of bryophyte or land plant.
The influence of climate change on the terrestrial vegetation health (condition) is one of the most significant problems of global change study. The vegetation activity plays a key role in the global carbon cycle. The authors investigated the relationship of the advanced very high resolution radiometer-normalized difference vegetation index (AVHRR-NDVI) with the large-scale climate variations on the inter-annual time scale during the period 1982-2000 for the growing seasons (April-October). A singular value decomposition analysis was applied to the NDVI and surface air temperature data in the time-domain to detect the most predominant modes coupling them. The first paired-modes explain 60.9%, 39.5% and 24.6% of the squared covariance between NDVI and temperature in spring (April-May), summer (June-August), and autumn (September-October), respectively, which implies that there is the highest NDVI sensitivity to temperature in spring and the lowest in autumn. The spatial centers, as revealed by the maximum or minimum vector values corresponding to the leading singular values, indicate the high sensitive regions. Only considering the mode 1, the sensitive center for spring is located in western Siberia and the neighbor eastern Europe with a sensitivity of about 0.308 0 NDVI/℃. For summer, there are no predominantly sensitive centers, and on average for the relatively high center over 1000-1200 E by 450-600 N, the sensitivity is 0.248 0 NDVI/℃. For autumn, the center is located over the high latitudes of eastern Asia (1100-1400 E, 550-650 N), and the sensitivity is 0.087 5 NDVI/℃. The coherent patters as revealed by the singular decomposition analysis remain the same when coarser resolution NDVI data were used, suggesting a robust and stable climate/vegetation relationship.
Using the closed-top tube incubation method, we examined the soil nitrogen (N) mineralization and nitrification in the primary Lithocarpus xylocarpus forest, a secondary oak forest and a tea plantation in the Ailao Mountain, Yunnan Province, China. This study was conducted in the dry season from November 20, 1998 to May 15, 1999. Results showed that there were significant differences among the three vegetation types in both net N mineralization and nitrification rates, and they also demonstrated temporal variation. The net ammonification rate (RA) was much higher than net nitrification rate (RN), and the latter was about 0.5%-10 % of the former. Our results indicated that incubation period, vegetation type and the location of plot all interactively affected RA, RN and net mineralization rate (RM ). We provided evidence that anthropogenic disturbances could result in changes of ecosystems processes such as N mineralization and nitrification rates. It is obvious that tea plantation and secondary growth forest have more physically (mainly temperature and moisture) controlled N transformation processes than the well-preserved primary L. xylocarpus forest, implying that the conservation of primary forest ecosystems in the Ailao Mountain region should be emphasized.
During the period of September 12, 1999 to September 24, 2000, we measured sap flow of eucalyptus (Eucalyptus urophylla S.T. Blake) plantations using heat pulse technique, and the relevant environmental vaiables, such as soil evaporation and canopy interception, etc, at Hetou and Jijia sites, Leizhou Peninsula, Guangdong Province. Based on the measurements of sap flow and estimates of evapotranspiration, the following can be concluded: (1) the maximum of diurnal xylem sap flux density (SFD) at Hetou, where covered with coarse-textured soils formed on Quaternary sediments, was almost twice of that at Jijia, where located on clay-rich soils derived from basalt; (2) SFD was highly correlated to water vapor pressure deficit (VPD) of ambient air near the canopy layer; (3) the correlation between SFD and air temperature also depends on soil properties and soil water potential; (4) the relative differences between measured and modeled evapotranspiration were small, being 5.26% at Hetou and 6.14% at Jijia; (5) the plantation transpiration accounted for 62.2% and 51.3% of the evapotranspiration at Hetou and Jijia, respectively; and (6) the averaged SFD per unit leaf area (ASPULA) was a good index to estimate the amount of water consumption of tree species.
In this study, the causes of the changes in lipid composition induced by different phosphate nutrient levels were investigated. Wheat plants were grown in phosphate-deficient and phosphate-sufficient conditions, respectively, and lipid composition in the leaves of 9-day-old and 16-day-old plants was analyzed. We found that phosphate deficiency induced a dramatic change in the lipid levels in photosynthetic membranes of wheat leaves and the extent of changes in lipid composition depended on the leaf ages. Phosphate deficiency induced a gradual decrease in PG and MGDG and a concomitant increase in DGDG and SQDG from the first leaf to the second and the third leaf on 16-day-old plants. In addition, as compared to leaves grown under phosphate sufficient solution, PG content in the first leaf of 16-day-old plants was significantly lower than that of 9-day-old leaf with 2.5 mol% versus 5.5 mol% when these plants were grown under phosphate deficient condition. From these results, it is suggested that the alternation in lipid composition in wheat leaves induced by phosphate deficiency is related to both lipid biosynthesis and PG degradation. PG decrease in younger leaves is mainly due to insufficient phosphate supply for PG biosynthesis, while PG degradation mainly resulted in the PG decrease in older leaves.
Peroxidases are known to play important roles in plant wound healing. Biochemical analysis and histochemical localization techniques were used to assess changes and distribution of peroxidases in the recovering bark after girdling in Eucommia ulmoides Oliv. Between 4 and 21 days after girdling (DAG), peroxidases activity in the girdled trees significantly increased by 30-40 times over that in ungirdled trees. During the whole bark recovery process (from 0 to 63 DAG), the peroxidase signal was not found in the tissue regions subjected to intense cell division activity (regenerating cambial zone and phellogen). However, high peroxidase activity was detected in the callus, cortex-like, mature phloem and xylem. Interestingly, it was shown that, in maturing xylem and phloem cells, there was respectively an inward and outward peroxidase activity gradient on both sides of the cambium zone. An isoelectric-focusing electrophoresis of the extracted protein displayed two isozyme bands of peroxidase: PODⅠand PODⅡ. PODⅠwas only detected in the xylem fraction and could play a role in xylem differentiation. PODⅡ was only identified in the recovering bark portion and could be more engaged in bark regeneration process. A relationship between IAA and peroxidase is also discussed.
The Arabidopsis WUSCHEL (WUS) gene plays a key role in the specification of the stem cells in the shoot apical meristem (SAM). A cDNA of WUS has been amplified with the RT-PCR approach from Arabidopsis. The plant overexpression vector was constructed. It was driven by a dual enhanced CaMV35S promoter. The construct was transformed into tobacco (Nicotiana tabacum L., via Agrobacterium mediation. Dramatic phenotypic changes appeared in the WUS overexpression transgenic plants. Aberrant cell divisions and ectopic organogenesis could be found in almost every aerial parts of the transgenic tobacco except the meristems and the inner two floral whorls. The data showed a highly conserved function of WUS in tobacco, and suggested that WUS is involved in organogenesis. The leaves were malformed, which strongly matched those only described previously for plants grown in the presence of polar auxin transport inhibitors. It suggested a possible function of WUS in leaf development. These results provide useful information for functional analysis of WUS and important biotechnological implication as well.
Electron microscopic observation revealed that poplar (Populus deltoides Marsh.) and winter wheat (Triticum aestivum L. cv. Seward 80004) plasmodesmatal structures significantly changed under short day (SD, 8 h light) and in winter period, and such changes differed also noticeably between these two woody and herbaceous plants. Under long day (LD, 16 h light), many plasmodesmata with strong stain appeared in the cell wall of both poplar apical buds and winter wheat young leaf tissues, and connections of cytoplasmic endoplasmic reticulum (ER) with the ER in some plasmodesmata were observed. In addition, the typical “neck type” plasmodesmata were observed in winter wheat young leaf tissues, and their central desmotubules (appressed-ER) could be clearly identified. Under SD, many poplar plasmodesmata showed only a partial structure in the cell wall and appeared to be discontinued; some plasmodesmata swelled in the mid-wall, forming the cavity, and no appressed-ER appeared. In winter wheat, however, no noticeable alterations of plasmodesmata occurred, and the plasmodesmatal structure essentially remained same as it was under LD. In winter period, poplar plasmodesmata had a similar morphology as those observed under SD, however, winter wheat manifested at least two types of significant plasmodesmatal alterations: one plugged by electron-dense materials and the other of reduced neck region compared to those under LD. The above dynamic difference of the two species plasmodesmata under SD and winter period revealed the difference of their dormancy development under those environmental conditions.
YrQz, a stripe rust disease resistance gene was identified in a common wheat (Triticum aestivum L.) line Qz180. This resistance was controlled by a single dominant gene, which was confirmed by genetic analysis of two F2 populations derived from the crosses using Qz180 and two susceptible parents (Mingxian 169 and WL1). Bulked segregant analysis using simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers was conducted in order to map the chromosomal location of YrQz. The results indicated that YrQz was located on the long arm of wheat chromosome 2B and resided in a region flanked by two SSR loci Xgwm388 and Xgwm526. Two AFLP markers P35M48(452) and P36M61 (163) were closely linked to YrQz with the genetic distance of 3.4 cM and 4.1 cM, respectively. To our knowledge, this is the first molecularly mapped stripe rust resistance gene on wheat chromosome 2B.
The paper reviews stomatal types observed in 500 species of angiosperms besides those described in the literature and deals with the problems of their structure, delimitation, nomenclature and classification. In view of the varied definitions available in the literature for subsidiaries, stomatal types and, the definition and delimitations being variously interpreted by different workers, a modified definition for the subsidiaries and stomata is presented. In accordance with the international code of nomenclature for plants, the names of the stomata widely in use are retained ( rule of priority ). They have been presently classified as pericytic, desmocytic, paracytic, diacytic, anisocytic, anisotricytic, isotricytic, tetracytic, staurocytic, anomocytic, cyclocytic and a good number of varieties under each type are presented. These stomatal types are recognised on the basis of their structure rather than its ontogenetic pathways.
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