Showing papers on "Sesbania rostrata published in 2009"

Calcium spiking patterns and the role of the calcium/calmodulin-dependent kinase CCaMK in lateral root base nodulation of Sesbania rostrata.

Abstract: Nodulation factor (NF) signal transduction in the legume-rhizobium symbiosis involves calcium oscillations that are instrumental in eliciting nodulation. To date, Ca2+ spiking has been studied exclusively in the intracellular bacterial invasion of growing root hairs in zone I. This mechanism is not the only one by which rhizobia gain entry into their hosts; the tropical legume Sesbania rostrata can be invaded intercellularly by rhizobia at cracks caused by lateral root emergence, and this process is associated with cell death for formation of infection pockets. We show that epidermal cells at lateral root bases respond to NFs with Ca2+ oscillations that are faster and more symmetrical than those observed during root hair invasion. Enhanced jasmonic acid or reduced ethylene levels slowed down the Ca2+ spiking frequency and stimulated intracellular root hair invasion by rhizobia, but prevented nodule formation. Hence, intracellular invasion in root hairs is linked with a very specific Ca2+ signature. In parallel experiments, we found that knockdown of the calcium/calmodulin-dependent protein kinase gene of S. rostrata abolished nodule development but not the formation of infection pockets by intercellular invasion at lateral root bases, suggesting that the colonization of the outer cortex is independent of Ca2+ spiking decoding.

Comparative Genome-Wide Transcriptional Profiling of Azorhizobium caulinodans ORS571 Grown under Free-Living and Symbiotic Conditions

Abstract: The whole-genome sequence of the endosymbiotic bacterium Azorhizobium caulinodans ORS571, which forms nitrogen-fixing nodules on the stems and roots of Sesbania rostrata, was recently determined. The sizes of the genome and symbiosis island are 5.4 Mb and 86.7 kb, respectively, and these sizes are the smallest among the sequenced rhizobia. In the present study, a whole-genome microarray of A. caulinodans was constructed, and transcriptomic analyses were performed on free-living cells grown in rich and minimal media and in bacteroids isolated from stem nodules. Transcriptional profiling showed that the genes involved in sulfur uptake and metabolism, acetone metabolism, and the biosynthesis of exopolysaccharide were highly expressed in bacteroids compared to the expression levels in free-living cells. Some mutants having Tn5 transposons within these genes with increased expression were obtained as nodule-deficient mutants in our previous study. A transcriptomic analysis was also performed on free-living cells grown in minimal medium supplemented with a flavonoid, naringenin, which is one of the most efficient inducers of A. caulinodans nod genes. Only 18 genes exhibited increased expression by the addition of naringenin, suggesting that the regulatory mechanism responding to the flavonoid could be simple in A. caulinodans. The combination of our genome-wide transcriptional profiling and our previous genome-wide mutagenesis study has revealed new aspects of nodule formation and maintenance.

The effects of green manure (Sesbania rostrata) on the growth and yield of rice

Abstract: Green manuring with an N2-fixing legume crop can meet a substantial portion of rice N requirement and provide organic matter to wetland rice soils to maintain soil fertility. Organic-N fertilizers in the form of flood-tolerant, leguminous, stem-nodulating Sesbania rostrata can be useful alternatives to resource- poor rice farmers if applied as green manure. Therefore, the accumulation of fixed N by this green manure, their effect on the performance and yield of rice was examined. Firstly, root and/or stem nodulation, nitro- gen fixation (acetylene-reducing activity), growth and N accumulation of S. rostrata as affected by inocula- tion site were studied in a pot experiment. The growth and N accumulation of S. rostrata in stem inocula- tion treatment was the highest. Therefore, stem inoculation method was used for growing S. rostrata to incorporate into the rice soils for the second experiment. In the second experiment, the effects of S. ros- trata green manure application on the growth and yield of rice were studied. Green manure treatments (2 and 4 plants pot -1 ) were compared to urea treatments (40 and 80 kg N ha -1 ) and no application treatment. Green manure treatments increased dry matter weight and grain weight of rice significantly over urea and no application treatments. All green manure treatments increased N uptake of the plant. It can be con- cluded that incorporation of green manure legumes can add large amount of biologically fixed N to rice soils. The effective utilization of biomass produced by the stem-nodulating S. rostrata could be an eco- nomically viable component of integrated nutrient management for increasing the yield components and yield of rice per unit area.

Immunolocalization of antioxidant enzymes in high‐pressure frozen root and stem nodules of Sesbania rostrata

Abstract: The activities and localizations of superoxide dismutases (SODs) were compared in root and stem nodules of the semi-aquatic legume Sesbania rostrata using gel-activity assays and immunogold labelling, respectively. Nodules were fixed by high-pressure freezing and dehydrated by freeze substitution. Stem nodules showed more total and specific SOD activities than root nodules because of the presence of chloroplastic CuZnSOD. Most of the total SOD activity of stem and root nodules resulted from 'cytosolic' CuZnSOD, localized in the cytoplasm and chromatin, and from MnSOD in the bacteroids and in the mitochondria of vascular tissue. FeSOD was present in nodule plastids and in leaf chloroplasts, and was found to be associated with chromatin. Superoxide production was detected histochemically in the vascular bundles and in the infected tissue of stem and root nodules, whereas peroxide accumulation was observed in the cortical cell walls and intercellular spaces, as well as within the infection threads of both nodule types. These data suggest a role of CuZnSOD and FeSOD in protecting nuclear DNA from reactive oxygen species and/or in modulating gene activity. The enhanced levels of CuZnSOD, MnSOD and superoxide production in vascular bundle cells are consistent with a role of CuZnSOD and superoxide in the lignification of xylem vessels, but also suggest additional functions in coping with superoxide production by the high respiratory activity of parenchyma cells.

Characterization of the Sesbania rostrata Phytochelatin Synthase Gene: Alternative Splicing and Function of Four Isoforms

Abstract: Phytochelatins (PCs) play an important role in detoxification of heavy metals in plants. PCs are synthesized from glutathione by phytochelatin synthase (PCS), a dipeptidyltransferase. Sesbania rostrata is a tropical legume plant that can tolerate high concentrations of Cd and Zn. In this study, the S. rostrata PCS gene (SrPCS) and cDNAs were isolated and characterized. Southern blot and sequence analysis revealed that a single copy of the SrPCS gene occurs in the S. rostrata genome, and produces four different SrPCS mRNAs and proteins, SrPCS1-SrPCS4, by alternative splicing of the SrPCS pre-mRNA. The SrPCS1 and SrPCS3 proteins conferred Cd tolerance when expressed in yeast cells, whereas the SrPCS2 and SrPCS4 proteins, which lack the catalytic triad and the N-terminal domains, did not. These results suggested that SrPCS1 and SrPCS3 have potential applications in genetic engineering of plants for enhancing heavy metal tolerance and phytoremediation of contaminated soils.

Enhanced adaptability of Sesbania rostrata to Pb/Zn tailings via stem nodulation.

Abstract: Sesbania rostrata is wellknown for its stem nodulation, but the roles of stem nodulation in root nodulation and adaptation of S. rostrata to Pb/Zn-enriched tailings environment has been poorly understood. We investigated the effects of inoculating (with stem nodule treatment) and non-inoculating (without stem nodule treatment) Azorhizobium caulinodans on the growth, root nodulation, and N fixation of S. rostrata grown on three different types of soil substrata: Pb/Zn tailings, garden soil amended tailings, and garden soil. The results showed that plant height, stem basal diameter, biomass, chlorophyll content, nitrogen content and N-accumulation per plant were 2.3%–4.9%, 2.2%–7.7%, 27.8%–72.2%, 17.1%–23.5%, 12.3%–34.2%, and 43.1%–131.2%, respectively, higher in treatments with stem nodule than those without stem nodule for the same soil substrate. With respect to soil substrata, all measurements had consistently higher values in tailings than in amended tailings and garden soil, indicating that the poorer the soil condition, the greater the contribution of stem nodule. In contrast, the number and fresh weight of root nodules on plants without stem nodule were 6.9–11.6 times and 5.8–29.0 times higher than those with stem nodule, respectively, especially with respect to the plants grew on Pb/Zn tailings. In general, stem nodulation favored plant growth and nitrogen fixation of S. rostrata, but suppressed root nodulation. With the ability of stem and root nodulation, S. rostrata can be used as a pioneer plant species for remediation of Pb/Zn tailings.

Factors Influencing Indole-3-Acetic Acid Biosynthesis of Root-Nodule Bacteria Isolated from Various Leguminous Plants

Abstract: Indole-3-acetic acid (IAA) biosynthesis was monitored in 50 isolates of root-nodule bacteria from 10 leguminous plants. The isolate DASA12010 from Sesbania rostrata and DASA23008 from Desmanthus virgatus produced the highest amount of IAA in Tris-TMRT medium supplemented with L-tryptophan at 25.16  0.81 µg/ml and 23.70  1.32 µg/ml, respectively. Five isolates producing the highest amount of IAA were selected to examine growth curve and IAA production. In all isolates tested, growth and IAA production started simultaneously. The highest levels of IAAwas produced in the stationary phase of growth. The influence of factors on IAA production was examined during a10-day cultivation. Dglucose (1.00 mg/ml), D-fructose (1.00 mg/ml), lactose (1.00 mg/ml), L-asparagine (1.00 mg/ml), glutamic acid (1.00 mg/ml) and ABA (0.01 mg/ml) decreased IAA production in some isolates, but increased IAA production in some isolates.While SDS (1.00 mg/ml) decreased IAA production in all isolates. The partial sequences of the 16S rDNA indicated high homology with members of Rhizobium sp., Sinorhizobium sp. and Mesorhizobium sp.

Cadmium and copper uptake and accumulation by Sesbania rostrata seedling, a N-fixing annual plant: implications for the mechanism of heavy metal tolerance

Abstract: Sesbania rostrata, an annual tropical legume, has been found to be tolerant to heavy metals, with an unknown mechanism. It is a promising candidate species for revegetation at mine tailings. In this study, sequential extractions with five buffers and strong acids were used to extract various chemical forms of cadmium and copper in S. rostrata, with or without Cd or Cu treatments, so that the mechanisms of tolerance and detoxification could be inferred. Both metals had low transition rates from roots to the aboveground of S. rostrata. The transition ratio of Cd (4.00%) was higher than that of Cu (1.46%). The proportion of NaCl extracted Cd (mostly in protein-binding forms) increased drastically in Cd treated plants from being undetectable in untreated plants. This suggests that Cd induced biochemical processes producing protein-like phytochelatins that served as a major mechanism for the high Cd tolerance of S. rostrata. The case for Cu was quite different, indicating that the mechanism for metal tolerance in S. rostrata is metal-specific. The proportion of water-insoluble Cu (e.g. oxalate and phosphate) in roots increased significantly with Cu treatment, which partially explains the tolerance of S. rostrata to Cu. However, how S. rostrata copes with the high biotic activity of inorganic salts of Cu, which increased in all parts of the plant under Cu stress, is a question for future studies. Sesbania rostrata is among the very few N-fixing plants tolerant to heavy metals. This study provides evidence for the detoxification mechanism of metals in Sesbania rostrata.

Growth of roots and yield as influenced by green manuring in rice-wheat cropping system

Abstract: An investigation on the effect of green manuring in rice-wheat cropping system was undertaken during May, 2001 to March 2002. Green manuring increased root length, root volume, root dry weight (i.e. root characters) of rice compared with control. Residual effect of green manuring along with added nitrogen also significantly influenced all the root characters of wheat compared with control. Green manuring and its residual effect increased most of the yield components except test weight, grain yield and straw yield of rice and wheat compared with control. However, among the different green manuring crops, Sesbania rostrata was, by far, the best one.

Enhanced adaptability of Sesbania rostrata to Pb/Zn tailings via stem nodulation

Abstract: Sesbania rostrata 为它在根生节和 S 的改编的茎生节的茎生节，而是角色是著名的。到 Pb/Zn-enriched 跟踪环境的 rostrata 糟糕被理解。我们调查了接种的效果(与茎小瘤处理) 并且非接种(没有茎小瘤处理) S 的生长，根生节，和 N 固定上的 Azorhizobium caulinodans。在土壤潜水艇阶层的三种不同类型上种的 rostrata：Pb/Zn 跟踪，花园土壤修改了跟踪，和花园土壤。结果显示出那植物高度，起源每植物的基础直径，生物资源，叶绿素内容，氮内容和N累积是23%49%，22%77%，278%722%，171%235%，123%342%，和431%1312%，分别地没有为一样的茎小瘤，更高比那些在有茎小瘤的处理玷污底层。关于土壤潜水艇阶层，大小有的所有更高一致地比在修改跟踪和花园土壤在跟踪珍视，显示那越差土壤条件，越 greater 茎小瘤的贡献。相反，数字和没有茎小瘤的植物上的根小瘤的新鲜重量比分别地，那些在 Pb/Zn 跟踪上特别关于植物与茎小瘤成长高是 69 116 次和 58 290 次。一般来说，茎生节赞成了植物生长和 S 的氮固定。rostrata，而是压制的根生节。与茎和根生节的能力， S。rostrata 能为 Pb/Zn 跟踪的补习被用作先驱植物种。