Plant growth-promoting potential of endophytic bacteria isolated from roots of wild <Emphasis Type="Italic">Dodonaea viscosa</Emphasis> L.

Dodonaea viscosa, a wild and perennial shrub that can tolerate harsh environmental conditions, was used for the isolation of its endophytic bacteria and their potential was explored for the promotion of Canola growth. The bacteria identified through 16S rRNA gene sequencing, belonged to ten different genera namely Inquilinus, Xanthomonas, Pseudomonas, Rhizobium, Brevundimonas, Microbacterium, Bacillus, Streptomyces, Agrococcus and Stenotrophomonas. All the strains produced small amount of IAA (indole acetic acid) in the absence of tryptophan and comparatively more in the presence of tryptophan. All the bacterial strains were positive for ammonia production, cellulase and pectinase activity, but few of them showed phosphate solubilization, siderophore and hydrogen cyanide production. Only three strains showed ACC (1-aminocyclopropane-1-carboxylate) deaminase activity when tested using in-vitro enzyme assay. Members of genera Bacillus, Pseudomonas and Streptomyces showed positive chitinase, protease and antifungal activity against two phytopathogenic fungi Aspergillus niger and Fusarium oxysoprum, while members of Xanthomonas, Pseudomonas and Bacillus showed significant root elongation of Canola which could be related with their positive plant-growth-promoting (PGP) traits. Among the three plant growth promoting Bacillus strains, B. idriensis is never reported before for its PGP activities. These results showed the potential of Dodonaea viscosa endophytic bacteria as PGPBs, which in future can be further explored for their host range/molecular mechanisms.     

Sunflower germination and growth behavior under various gamma radiation absorbed doses

Gamma radiation, various absorbed doses (0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 krad) effects were evaluated on sunflower (Helianthus annus. L.) germination and growth characteristics. Sunflower healthy seeds were exposed to gamma radiation source Co⁶⁰ at nuclear institute for food and agriculture and exposed seeds were grown under controlled laboratory conditions. In comparison to control, gamma radiation absorbed doses affected the measured response positively i.e., radical length, plumule length, number of roots, seedling fresh weight, seedling dry weight, germination percentage, time of germination and diameter of hypocotyl of sunflower enhanced up to 83.15%, 70.32%, 73.03%, 4.80%, 3.26%, 72.0%, ? 18.88% and 12.58%, respectively. The time of germination, fresh weight and percent moisture contents enhanced insignificantly, however, the response was higher than control. All gamma radiation absorbed doses showed a stimulatory effect on sunflower germination and seedling growth characteristics. The low gamma radiation absorbed doses were found to be more effective versus higher doses for enhancing the germination and growth characteristics of sunflower. In view of positive effect of gamma radiation of sunflower germination and growth characteristics, it is concluded that this techniques could possibly be used for the enhancement of germination, growth and ultimately yield in sunflower in areas where germination is low due to unfavorable conditions.     

Insulin stimulates phosphatidylinositol 3-phosphate production via the activation of Rab5

Phosphatidylinositol 3-phosphate (PI(3)P) plays an important role in insulin-stimulated glucose uptake. Insulin promotes the production of PI(3)P at the plasma membrane by a process dependent on TC10 activation. Here, we report that insulin-stimulated PI(3)P production requires the activation of Rab5, a small GTPase that plays a critical role in phosphoinositide synthesis and turnover. This activation occurs at the plasma membrane and is downstream of TC10. TC10 stimulates Rab5 activity via the recruitment of GAPEX-5, a VPS9 domain-containing guanyl nucleotide exchange factor that forms a complex with TC10. Although overexpression of plasma membrane-localized GAPEX-5 or constitutively active Rab5 promotes PI(3)P formation, knockdown of GAPEX-5 or overexpression of a dominant negative Rab5 mutant blocks the effects of insulin or TC10 on this process. Concomitant with its effect on PI(3)P levels, the knockdown of GAPEX-5 blocks insulin-stimulated Glut4 translocation and glucose uptake. Together, these studies suggest that the TC10/GAPEX-5/Rab5 axis mediates insulin-stimulated production of PI(3)P, which regulates trafficking of Glut4 vesicles.     

Plant growth promotion and Penicillium citrinum

Background

Lamivudine is an oral nucleoside analogue widely used for the treatment of chronic hepatitis B. The main limitation of lamivudine use is the selection of resistant mutations that increases with time of utilization. Hepatitis B virus (HBV) isolates have been classified into eight genotypes (A to H) with distinct geographical distributions. HBV genotypes may also influence pathogenic properties and therapeutic features. Here, we analyzed the HBV genotype distribution and the nature and frequency of lamivudine resistant mutations among 36 patients submitted to lamivudine treatment for 12 to 84 months.

Results

Half of the patients were homosexual men. Only 4/36 (11%) patients were HBV DNA negative. As expected for a Brazilian group, genotypes A (24/32 positive individuals, 75%), D (3/32, 9.3%) and F (1/32, 3%) were present. One sample was from genotype C, which is a genotype rarely found in Brazil. Three samples were from genotype G, which had not been previously detected in Brazil. Lamivudine resistance mutations were identified in 20/32 (62%) HBV DNA positive samples. Mean HBV loads of patients with and without lamivudine resistance mutations were not very different (2.7 × 10⁷ and 6.9 × 10⁷ copies/mL, respectively). Fifteen patients showed the L180M/M204V lamivudine resistant double mutation. The triple mutant rt173V/180M/204V, which acts as a vaccine escape mutant, was found in two individuals. The three isolates of genotype G were entirely sequenced. All three showed the double mutation L180M/M204V and displayed a large genetic divergence when compared with other full-length genotype G isolates.

Conclusion

A high (55%) proportion of patients submitted to long term lamivudine therapy displayed resistant mutations, with elevated viral load. The potential of transmission of such HBV mutants should be monitored. The identification of genotypes C and G, rarely detected in South America, seems to indicate a genotype distribution different to that observed in non treated patients. Disparities in routes of transmission (genotype G seems to be linked to homosexual behavior) and in pathogenic properties (genotype C is very aggressive) among HBV genotypes may explain the presence of rare genotypes in the present work.