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Leaf-residing Methylobacterium species fix nitrogen and promote biomass and seed production in Jatropha curcas.

ABSTRACT: BACKGROUND:Jatropha curcas L. (Jatropha) is a potential biodiesel crop that can be cultivated on marginal land because of its strong tolerance to drought and low soil nutrient content. However, seed yield remains low. To enhance the commercial viability and green index of Jatropha biofuel, a systemic and coordinated approach must be adopted to improve seed oil and biomass productivity. Here, we present our investigations on the Jatropha-associated nitrogen-fixing bacteria with an aim to understand and exploit the unique biology of this plant from the perspective of plant-microbe interactions. RESULTS:An analysis of 1017 endophytic bacterial isolates derived from different parts of Jatropha revealed that diazotrophs were abundant and diversely distributed into five classes belonging to ?, ?, ?-Proteobacteria, Actinobacteria and Firmicutes. Methylobacterium species accounted for 69.1 % of endophytic bacterial isolates in leaves and surprisingly, 30.2 % which were able to fix nitrogen that inhabit in leaves. Among the Methylobacterium isolates, strain L2-4 was characterized in detail. Phylogenetically, strain L2-4 is closely related to M. radiotolerans and showed strong molybdenum-iron dependent acetylene reduction (AR) activity in vitro and in planta. Foliar spray of L2-4 led to successful colonization on both leaf surface and in internal tissues of systemic leaves and significantly improved plant height, leaf number, chlorophyll content and stem volume. Importantly, seed production was improved by 222.2 and 96.3 % in plants potted in sterilized and non-sterilized soil, respectively. Seed yield increase was associated with an increase in female-male flower ratio. CONCLUSION:The ability of Methylobacterium to fix nitrogen and colonize leaf tissues serves as an important trait for Jatropha. This bacteria-plant interaction may significantly contribute to Jatropha's tolerance to low soil nutrient content. Strain L2-4 opens a new possibility to improve plant's nitrogen supply from the leaves and may be exploited to significantly improve the productivity and Green Index of Jatropha biofuel.

SUBMITTER: Madhaiyan M

PROVIDER: S-EPMC4687150 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Project description:BackgroundJatropha curcas, a tropical shrub, is a promising biofuel crop, which produces seeds with high content of oil and protein. To better understand the maturation process of J. curcas seeds and to improve its agronomic performance, a two-step approach was performed in six different maturation stages of seeds: 1) generation of the entire transcriptome of J. curcas seeds using 454-Roche sequencing of a cDNA library, 2) comparison of transcriptional expression levels using a custom Agilent 8x60K oligonucleotide microarray.ResultsA total of 793,875 high-quality reads were assembled into 19,382 unique full-length contigs, of which 13,507 could be annotated with Gene Ontology (GO) terms. Microarray data analysis identified 9111 probes (out of 57,842 probes), which were differentially expressed between the six maturation stages. The expression results were validated for 75 selected transcripts based on expression levels, predicted function, pathway, and length. Result from cluster analyses showed that transcripts associated with fatty acid, flavonoid, and phenylpropanoid biosynthesis were over-represented in the early stages, while those of lipid storage were over-represented in the late stages. Expression analyses of different maturation stages of J. curcas seed showed that most changes in transcript abundance occurred between the two last stages, suggesting that the timing of metabolic pathways during seed maturation in J. curcas occurs in late stages. The co-expression results showed that the hubs (CB5-D, CDR1, TT8, DFR, HVA22) with the highest number of edges, associated with fatty acid and flavonoid biosynthesis, are showing a decrease in their expression during seed maturation. Furthermore, seed development and hormone pathways are significantly well connected.ConclusionThe obtained results revealed differentially expressed sequences (DESs) regulating important pathways related to seed maturation, which could contribute to the understanding of the complex regulatory network during seed maturation with the focus on lipid, flavonoid and phenylpropanoid biosynthesis. This study provides detailed information on transcriptional changes during J. curcas seed maturation and provides a starting point for a genomic survey of seed quality traits. The results highlighted specific genes and processes relevant to the molecular mechanisms involved in Jatropha seed maturation. These data can also be utilized regarding other Euphorbiaceae species.

Project description:This work present a large data set related to a non-target LC-MS/MS high-resolution metabolome analysis of the leaves and roots of Jatropha curcas. Besides its high protein contents, the seeds of J. curcas are also rich in oil, so the seeds are considered a potential source of raw material to produce biodiesel and a source of food for farm animals. The full exploitation of these potentials is hampered by the presence of a highly toxic class of diterpenoids, the phorbol esters (PE), both in the oil and in the seedcake derived from the extraction of the oil. The seeds are known to possess 6 different PE, and although their structures have been known for almost 30 years, the biosynthetic pathway of each one remains undetermined. However, there are indications that the enzyme casbene synthase is responsible for the first biosynthetic step. The leaves and roots of this species are also rich in several classes of diterpenes which by themselves have pharmacological potential not yet explored. For our analysis, we used two genotypes that are contrasting regarding the contents of phorbol esters: One genotype has a high level of phorbol esters (HPE), while the other has low levels of phorbol esters in the seeds (LPE). We were able to detect a total of 2032 features and applied multivariate statistical methods, such as PCA and heatmap with hierarchical clustering to analyze and visualize the deposition pattern of metabolites, with a focus on terpenoids. Our analysis allowed us to several new findings regarding the synthesis of PE in J. curcas, such as that only in HPE genotypes roots are found diterpenes with the tigliane skeleton. In contrast, the LPE genotype has a higher concentration and diversity of sesquiterpenes. Taking into consideration the results of our previous proteome analysis of seeds, roots, and leaves and the metabolome data presented in the manuscript, we suggest that the absence of PE in the LPE genotype may be the result of the absence of the enzymes responsible for the final biosynthetic steps, which in turn lead to the accumulation of sesquiterpenes this genotype.

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Leaf-residing Methylobacterium species fix nitrogen and promote biomass and seed production in Jatropha curcas.

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