Ca2+ and reactive oxygen species are involved in the defense responses of rice callus culture to rice blast disease

The role of Ca2+ and reactive oxygen species in the defense responses of callus cultures of rice (Oryza sativa L., cv. Zenith) to infection with avirulent strain of rice blast fungus (Magnaporthe grisea, strain Ina168) was investigated. It was observed that rice calli, especially after mild blast infection, exude substances (diffusate) that inhibit spore germination of the avirulent blast fungus. This fungitoxic calli diffusate led to superoxide dismutase-sensitive reduction of Nitro-blue-tetrazolium. Treatment of rice calli with crude elicitor from the blast fungus also led to hypersensitive necrotic response. Addition of antioxidant reagents diminishes the necrotic response of calli to the elictor treatment, implicating the involvement of reactive oxygen species in the hypersensitive necrotic response. When ethyleneglycoltetraacetic acid (Ca2+ chelator) or LaCl3 (Ca2+channel blocker) was added, the necrotic response of calli to elicitor treatment was also significantly weakened, implying the involvement of Ca2+ in the defense response. Key Words: Oryza sativa, Magnaporthe grisea, hypersensitive response, reactive oxygen species, calcium. African Journal of Biotechnology Vol.3(1) 2004: 76-8

Explant establishment for callus initiation of a Nigerian “endangered” leafy vegetable, Gnetum africanum (WILLD)

A prerequisite for successful in vitro culture is the establishment of an aseptic technique, thus the experiment was to investigate suitable sterilization regimes for the leaf explants of Gnetum africanum, an endangered green leafy vegetable. Three sterilization regimes were tested to establish the best regime using three to four days old leaves. The surface sterilized explants were later aseptically introduced onto the surfaces of sterile Murashige and Skoog agar media, incubated at 25°C for three weeks in the growth chamber. 100% sterility was observed from the regime which was significantly different (P<0.05) from the other two regimes thus the best regime adopted for further experiments was; washing in two drops of Tween 20/100 mls of sterile water, soaking in 70% ethanol for 2 min and later in 1% sodium hypochlorite for 20 min. Fungal contaminants responsible for in vitro contaminations was also investigated and possible isolates were identified as Asperigilus niger (28.71%); A. flavus (26.73%); Rhyziopus spp. (24.75%) and Mucor Spp (19.81%) respectively.Keywords: Gnetum africanum, A. niger, in vitro culture, green leafy vegetableAfrican Journal of Biotechnology Vol. 12(28), pp. 4473-447

Optimization of protocols for DNA extraction and RAPD analysis in West African fonio (Digitaria exilis and Digitaria iburua ) germplasm characterization

Fonio is an important indigenous grain crop of West Africa, but the extent of genetic diversity in fonio, its origin and phylogeny are not well understood. DNA markers allow precise characterization of plant germplasm accessions, but there is no literature report of their use in fonio. This paper reports theresult of protocol optimization research for DNA isolation and RAPD analyses in fonio. High quality DNA was successfully isolated and RAPD was effectively used to study genetic similarity among fonio accessions. This result might stimulate the application of DNA markers to investigate the origin and phylogeny of fonio in Africa

Global profiling of co- and post-translationally N-myristoylated proteomes in human cells

Protein N-myristoylation is a ubiquitous co- and post-translational modification that has been implicated in the development and progression of a range of human diseases. Here, we report the global N-myristoylated proteome in human cells determined using quantitative chemical proteomics combined with potent and specific human N-myristoyltransferase (NMT) inhibition. Global quantification of N-myristoylation during normal growth or apoptosis allowed the identification of >100 N-myristoylated proteins, >95% of which are identified for the first time at endogenous levels. Furthermore, quantitative dose response for inhibition of N-myristoylation is determined for >70 substrates simultaneously across the proteome. Small-molecule inhibition through a conserved substrate-binding pocket is also demonstrated by solving the crystal structures of inhibitor-bound NMT1 and NMT2. The presented data substantially expand the known repertoire of co- and post-translational N-myristoylation in addition to validating tools for the pharmacological inhibition of NMT in living cells

Environmental and genotypic effects on the growth rate of in vitro cassava plantlet (Manihot esceulenta)

Two varieties of cassava were evaluated in vitro in the screen house and culture room using five different media treatment. Each treatment was replicated 12 times and observed for 5 weeks before subculturing.There were significant differences in the growth rate of plantlets in different media, which suggests an interaction between treatments and environments. However, F-probability on survival shows that TMS 188/00106 was significantly different from TMS 083/00125 in the culture room than in the screen house. The study confirms that cassava tissue culture can be raised in the screen house but suggests that plantlet should be allowed to survive in the culture room before transferring to the screenhouse for further growth

Shoot tip regeneration and optimization of Agrobacterium tumefaciens-mediated transformation of Broccoli (Brassica oleracea var. italica) cv. Green Marvel

A protocol of plant regeneration from shoot tips and optimization of Agrobacterium tumefaciens-mediated transformation of broccoli (Brassica oleracea var. italica) cv. Green Marvel have been developed. Shoot tip response was assessed on Murashige and Skoog (MS) medium supplemented with different concentrations of zeatin. The highest regeneration with a maximum of 13 shoots per explant was obtained on MS medium containing 1.5 mg l-1 zeatin. Primary selection of putative transformed explants was performed on the optimized regeneration medium (MS medium containing 1.5 mg l-1 zeatin and 80 mg l-1 kanamycin) for 60 days. The effects of preculture, acetosyringone and growth of bacterial culture were studied. Explants precultured on callus induction medium for 4 days prior to inoculation with A. tumefaciens with 200 lM acetosyringone resulted in improved transformation frequency. The Agrobacterium culture dilution of 1:5 and inoculation time of 30 min increased the efficiency of transformation of shoot tip explants. The results also indicated that 150 mg l-1 ampicillin alone was adequate to eradicate Agrobacterium growth in the SRM incorporated with the respective minimum inhibitory concentration of 80 mg l-1 kanamycin. The polymerase chain reaction (PCR) and Southern blot assays confirmed the transgenic status of the broccoli cv. Green Marvel regenerants. A transformation efficiency of 5 % was achieved based on the positive PCR results using the optimized procedure. The expression of luciferase reporter gene in the transformed cells and the transcription of AtHSP101 using RT-PCR further confirmed the transgenic status of the regenerated plants