Potential effects of plant growth promoting rhizobacteria (Pseudomonas fluorescens) on cowpea seedling health and damping off disease control

Damping off caused by Sclerotium rolfsii on cowpea results in yield losses with serious socioeconomic implication. Induction of defense responses by plant growth promoting rhizobacteria (PGPR) is largely associated with the production of defense enzyme phenyl ammonia lyase (PAL) and oxidative enzymes like peroxidases (PO) and poly phenol oxidase (PPO). In the present study, the effect of plant growth promoting rhizobacteria (Pseudomonas fluorescence (bv. V)) on both damping off development and growth parameters in cow pea seedlings were investigated. The best reduction in pre and post emergence damping off in cowpea seedlings was observed in BCPF 8-treated samples. Seed bacterization with BCPF 8 significantly increased peroxidase (PO), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) activities. The activation of these defense reactions by BCPF 8 was correlated with an enhanced resistance to damping-off caused by S. rolfsii. This study demonstrated the ability of the rhizobacteria BCPF 8 to induce systemic resistance in cowpea, suggesting that this legume is an Induced systemic resistance (ISR)-positive plant.Keywords: Plant growth promoting rhizobacteria, vigour index, induction of systemic resistance, peroxidase, polyphenol oxidase, phenyl ammonia lyase, phenolicsAfrican Journal of Biotechnology Vol. 12(15), pp. 1853-1861

Biochemical responses during the pathogenesis of Sclerotium rolfsii on cowpea

The hypersensitive reaction (HR), one of the most efficient and visible parts of the defense mechanisms in nature against invading pathogens, is associated with a coordinated and integrated set of metabolic alterations which are instrumental in impeding further pathogen ingress or alleviating stress. It includes a variety of novel proteins and secondary metabolites. This study aimed to examine the induction of different stress related enzymes like phenyl alanineammonia lyase (PAL), chitinase, β-1,3 glucanase, oxidative enzymes like peroxidases (POD), poly phenol oxidases (PPO) and phenolics after inoculation of Sclerotium rolfsii in collar region of 30 days old cowpea plant. Scanning electron microscopy strengthened the presence of mycelial network in xylem vessel of infected collar region of cowpea at three days after inoculation. Cowpea plants inoculated with S. rolfsii isolate showed significantly increased POD, PPO, PAL, chitinase and β-1, 3-glucanase activities at different days after inoculation. In the present study, there was a greater accumulation of total phenol in cowpea plants observed up to five days after inoculation. The highest activity of POD, SOD was found in three days after inoculation and PPO activity was greater in five days after inoculation and thereafter, the activities of such enzymes steadily decreased. It was due to susceptible interaction of S. rolfsii ingression in cowpea. The correlation study between disease progression and changes in activity of different defense relatedenzymes showed that POD and chitinase were significantly associated with susceptible host pathogenic interaction in cowpea against S. rolfsii.Keywords: Cowpea, Sclerotium rolfsii, defense-related enzymes, phenolics, pathogenesis related proteins, scanning electron microscopyAfrican Journal of BiotechnologyVol. 12(25), pp. 3968-397

FRET-Based Identification of mRNAs Undergoing Translation

We present proof-of-concept in vitro results demonstrating the feasibility of using single molecule fluorescence resonance energy transfer (smFRET) measurements to distinguish, in real time, between individual ribosomes programmed with several different, short mRNAs. For these measurements we use either the FRET signal generated between two tRNAs labeled with different fluorophores bound simultaneously in adjacent sites to the ribosome (tRNA-tRNA FRET) or the FRET signal generated between a labeled tRNA bound to the ribosome and a fluorescent derivative of ribosomal protein L1 (L1-tRNA FRET). With either technique, criteria were developed to identify the mRNAs, taking into account the relative activity of the mRNAs. These criteria enabled identification of the mRNA being translated by a given ribosome to within 95% confidence intervals based on the number of identified FRET traces. To upgrade the approach for natural mRNAs or more complex mixtures, the stoichiometry of labeling should be enhanced and photobleaching reduced. The potential for porting these methods into living cells is discussed

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