Regulation of L-proline biosynthesis, signal transduction, transport, accumulation and its vital role in plants during variable environmental conditions.

BACKGROUND: In response to various environmental stresses, many plant species synthesize L-proline in the cytosol and accumulates in the chloroplasts. L-Proline accumulation in plants is a well-recognized physiological reaction to osmotic stress prompted by salinity, drought and other abiotic stresses. L-Proline plays several protective functions such as osmoprotectant, stabilizing cellular structures, enzymes, and scavenging reactive oxygen species (ROS), and keeps up redox balance in adverse situations. In addition, ample-studied osmoprotective capacity, L-proline has been also ensnared in the regulation of plant improvement, including flowering, pollen, embryo, and leaf enlargement. SCOPE AND CONCLUSIONS: Albeit, ample is now well-known about L-proline metabolism, but certain characteristics of its biological roles are still indistinct. In the present review, we discuss the L-proline accumulation, metabolism, signaling, transport and regulation in the plants. We also discuss the effects of exogenous L-proline during different environmental conditions. L-Proline biosynthesis and catabolism are controlled by several cellular mechanisms, of which we identify only very fewer mechanisms. So, in the future, there is a requirement to identify such types of cellular mechanisms.

Synergistic effects of plant defense elicitors and Trichoderma harzianum on enhanced induction of antioxidant defense system in tomato against Fusarium wilt disease.

Plant defense against their pathogens can be induced by a complex network of different inducers. The present study investigates the synergistic effect of Trichoderma harzianum, exogenous salicylic acid (SA) and methyl jasmonate (MeJA) over the response and regulation of the antioxidant defense mechanisms and lipid peroxidation in tomato plants against Fusarium wilt disease. In the present work, tomato plants were infected by Fusarium oxysporum f. sp. lycopersici 3 days after inoculated with T. harzianum and/or sprayed daily for 3 days with chemical inducers (SA and MeJA). Plants were analysed at 0, 24, 48, 72 and 96 h after inoculation with Fusarium oxysporum f. sp. lycopersici. Infection of tomato plants by pathogen led to strong reduction in the dry weight of roots and shoots with the enhanced concentration of H2O2 and varying degree of lipid peroxidation. Concurrently, exogenous SA, when applied with pathogen greatly enhanced H2O2 content as well as activities of antioxidant enzymes except catalase (CAT) and ascorbate peroxidase (APx). The pathogen challenged plants pretreated with T. harzianum and MeJA together exhibited less lipid peroxidation and as well as the elevated level of ascorbic acid and enhanced activities of antioxidant enzymes. All applied treatments protected tomato seedlings against Fusarium wilt disease but the percentage of protection was found higher in plants pretreated with the combination of T. harzianum and chemical inducers.

Isolation, characterization and toxicological potential of Alternaria-mycotoxins (TeA, AOH and AME) in different Alternaria species from various regions of India.

Alternaria species produce various sorts of toxic metabolites during their active growth and causes severe diseases in many plants by limiting their productivity. These toxic metabolites incorporate various mycotoxins comprising of dibenzo-α-pyrone and some tetramic acid derivatives. In this study, we have screened out total 48 isolates of Alternaria from different plants belonging to different locations in India, on the basis of their pathogenic nature. Pathogenicity testing of these 48 strains on susceptible tomato variety (CO-3) showed 27.08% of the strains were highly pathogenic, 35.41% moderately pathogenic and 37.5% were less pathogenic. Phylogenetic analysis showed the presence of at least eight evolutionary cluster of the pathogen. Toxins (TeA, AOH and AME) were isolated, purified on the basis of column chromatography and TLC, and further confirmed by the HPLC-UV chromatograms using standards. The final detection of toxins was done by the LC-MS/MS analysis by their mass/charge ratio. The present study develops an approach to classify the toxicogenic effect of each of the individual mycotoxins on tomato plant and focuses their differential susceptibility to develop disease symptoms. This study represents the report of the natural occurrence and distribution of Alternaria toxins in various plants from India.

Contamination of potable water by enterotoxigenic Escherichia coli: qPCR based culture-free detection and quantification.

Tourists visiting to endemic zones may acquire Enterotoxigenic Escherichia coli (ETEC) infection resulting into diarrhea due to consumption of contaminated potable waters. In this study, a qPCR assay (SYBR Green), targeting LT1 and ST1 genes was designed to quantify ETEC in potable waters derived from civic water supply. The assay could detect lowest 1CFU/PCR targeting LT1/ST1 gene from ten-fold diluted culture of the reference strain (E. coli MTCC 723) and is ten-fold more sensitive than the conventional PCR. The quantification of the ETEC in potable waters collected from civic supply of a major city of the northern India exhibiting high flow of tourists reveals that all the sites that ran along sewage line were contaminated by the ETEC. Contamination was due to percolation of sewage. The assay could be used for the regular monitoring of potable water in places exhibiting heavy flow of tourists to prevent ETEC induced diarrhea.

Spectroscopic characterization and identification of Pseudomonas fluorescens mediated metabolic products of Acid Yellow-9.

Pseudomonas flourescens NCIM 2100 was obtained from NCL, Pune, India, that was adapted to growth on 4 amino 1-1 azo benzene 3,4-Disulfonic acid. This strains was tested by UV, (1)H NMR, and IR spectroscopy for its ability to degrade the dye which resulted in to sulfonated analogs namely p-amino benzene sulfonic acid sodium salt and 2,4 diamino benzene sulfonic acid sodium salt. These compound further changed to either 2,4 dihydroxy benzene sulfonic acid sodium salt or 2 amino 4 hydroxy benzene sulfonic acid sodium salt, or 4 amino 2 hydroxy benzene sulfonic acid sodium salt. These breakdown compounds were non toxic in nature.

Antagonism of Pseudomonas cepacia against phytopathogenic fungi.

Two strains of Pseudomonas cepacia, RJ3 and ATCC 52796, have been identified as potential antagonists of fungal plant pathogens. We have compared the antagonistic activity of these two strains against various fungal pathogens. Although both strains displayed high levels of antagonism, ATCC 52796 was slightly more antagonistic than RJ3. The antagonist from RJ3 has been identified as the antifungal compound pyrrolnitrin after purification by HPLC and characterization by UV, IR, NMR, and mass spectroscopy. Both strains also antagonized the fungi by production of volatile compound(s), which have not yet been identified. Both strains are similar with respect to in vitro antagonism, mechanism of antagonism, and sensitivity to antibiotics.

Transposon Tn5-259 mutagenesis of Pseudomonas cepacia to isolate mutants deficient in antifungal activity.

Transposon Tn5-259 was inserted into the chromosome of Pseudomonas cepacia by mating with an Escherichia coli strain harboring a self-mobilizable, temperature-sensitive plasmid, pME12. Data from Southern blots and auxotroph analyses indicated that a single copy of the transposon was inserted in several places into the chromosome of P. cepacia. Among 1500 Tn5-259 transconjugants, only one mutant was found to be defective in the production of an antifungal compound, pyrrolnitrin. In addition, this mutant lost its ability to antagonize fungal phytopathogens. Using flanking DNA of the mutated gene as a probe, we have isolated four overlapping cosmid clones from a genomic library of P. cepacia. However, we were unable to complement the mutant because of difficulty in mobilizing the cosmids from E. coli to P. cepacia.

Environmental factors affecting the antagonism of Pseudomonas cepacia against Trichoderma viride.

Antagonistic activity of the bacterium Pseudomonas cepacia against Trichoderma viride was greatly influenced by nutritional and environmental conditions. Xylose and trehalose strongly enhanced the antifungal activity of P. cepacia, whereas mannitol and glucose had little effect. The carbon sources that enhanced the antagonistic activity also inhibited sporulation of T. viride. Antagonism of P. cepacia was enhanced by ammonium nitrogen; however, with nitrite or nitrate there was only a little antagonism. The antagonism of P. cepacia was optimal at pH 5.0. Although P. cepacia showed maximum antagonism against T. viride at 37 degrees C, the antagonism was fairly good at temperatures as low as 18 degrees C, indicating that there is a broad range of temperature for the antifungal activity of P. cepacia.