Jesse Machuka's research while affiliated with Kenyatta University and other places

The genomes of various organisms have now been fully sequenced, including human and representative microbial, insect, animal and plant genomes. The research challenge in the post-genome era is to establish how genes and proteins function to bring about changes in phenotype. Some of these phenotypes, and products obtainable through modern biotechnology, are of crucial importance within the context of sustainable development of African economies. The greatest ultimate impact will be in agricultural genomics, especially for marker assisted selection and breeding programs in crop and animal agriculture, development of animal disease diagnostics and vaccines, crop genetic engineering to overcome abiotic and biotic stresses and for improvement of the nutritional quality of major food staples. It is imperative that African countries become key players in the "gene revolution" since the cost of leaving them behind may be higher than the cost of empowering them to become players in mastering and benefiting from biotechnology. This paper highlights the potential impact of the latest advances in modern biotechnology, including genomics and bioinformatics, on sustainable development, in line with the goals of the New Partnership for Africa's Development (NEPAD). These include acceleration of economic growth, eradication of widespread and severe poverty and efforts to halt the marginalization of Africa in the globalization process.

The biological effects of affinity purified seed lectin from African yam bean, Sphenostylis stenocarpa (Harms), were tested on Clavigralla tomentosicollis (Stal) in an artificial seed system. S. stenocarpa was extracted from two African yam bean accessions: Enugu 95-3 and Enugu 98-2. Lectins from both accessions were highly toxic to the insect at 1.0% dry weight. For nymphs feeding on Enugu 95-3 and Enugu 98-2, survival ranged from 16.0 to 24.0% and 4.0 to 16.0% at 1.0 and 2.0% dry weight dietary lectin levels, respectively. From 4.0 to 8.0% dry weight of both lectins, no nymph survived up to 6 d after infestation. At 1.0% dry weights of Enugu 95-3 and Enugu 98-2 lectins, there was a significant delay in total developmental time (5.35 and 5.18 d), reduced survival (24.0% and 16.0%), and reduced growth (0.15+/-0.02 and 0.14+/-0.01) and resistance (61.85+/-9.78 and 57.79+/-3.80) indices, respectively. S. stenocarpa from Enugu 98-2 was the most toxic, with an LD50 of 0.43%, compared with an LD50 of 0.65% for S. stenocarpa from Enugu 95-3. The results of this investigation indicate that there exists in C. tomentosicollis physiological systems vulnerable to African yam bean lectins.

Few would disagree that the many claims and counterclaims concerning what biotechnology can or cannot do to solve Africa's food insecurity problem have mainly been made by non-Africans. It is no wonder that Florence Wambugu's (1999) excellent article titled "Why Africa needs agricultural biotech" is now widely cited by those who support the view that developing countries, particularly in SubSaharan Africa (SSA), stand to gain the most from modern biotechnology applications. The article explained in a nutshell some of the potential benefits Africa stands to gain by embracing biotechnology. Although opin- ions differ regarding the role biotechnology can play in African development, all (hopefully!) must agree about the urgency to eradicate the perpetual cycle of hunger, malnutrition, and death in a world of plenty. It is an acknowledged fact that Africa is endowed with tremendous natural (including genetic) and hu- man wealth that has yet to be harnessed to the benefit of its people. Sadly, some of this reservoir of re- sources have been disintegrating and the trend is bound to accelerate unless urgent measures are taken to stop and reverse this drift. Since farming is the most important source of income and sustenance for about three quarters of the population of SSA, there is no doubt that agricultural biotechnology (agbio- tech) can make very substantial contributions toward increasing food production by rural resource-poor farmers, while preserving declining resources such as forests, soil, water, and arable land (Bunders and Broerse, 1991). However, application of modern bio- technology tools is not likely to significantly reduce the contributions that conventional disciplines such as soil science, breeding, plant health management, agronomy, agricultural economics, and social sci- ences make to enhance crop production. In villages, constraints to crop production include pests, diseases, weeds, environmental degradation, soil nutrient depletion, low fertilizer inputs, inade- quate food processing amenities, poor roads to mar- kets, and general lack of information to make science- based decisions that underlie farming methodologies and systems. For some of these constraints, biotech-

Seed proteins were extracted from the African yam bean (AYB; Sphenostylis stenocarpa), an underutilized West African food legume. One- and two-dimensional polyacrylamide gel electrophoresis was then used to analyze the albumin fraction, galactose-specific lectins purified on immobilized galactose-Sepharose 4B, and abundant non-lectin seed proteins left over following affinity chromatography. N-terminal sequencing of prominently resolved polypetide bands led to identification of proteins having sequence homology with characterized legume seed proteins, namely, mung bean seed albumin, pea alpha-fucosidase, soybean Kunitz-type trypsin inhibitor, an endochitinase, pea pathogenesis-related protein, and/or cowpea seed storage proteins. Minor lectin-like proteins lacking hemagglutinating activity against rabbit and human erythrocytes were also identified. Because proteins such as protease inhibitors, chitinases, pathogenesis-related proteins, and lectins are known to have antimetabolic effects, the findings from this study may have relevance in the acceptability, adoption, and utilization of AYB as human food.

Artificial feeding assays were used to study the effect of purified galactose-specific lectins from African yam beans (Sphenostylis stenocarpa) on development of larvae of the cowpea weevil, Callosobruchus maculatus (Coleoptera : Bruchidae) and the legume pod-borer, Maruca vitrata (Lepidoptera : Pyrialidae). Inhibition of development of C. maculatus was observed when larvae were fed on artificial cowpea seeds containing 0.2%, 2.0% and 5.0% (wt/wt) of dietary lectin. Larval mortality was between 30% and 88%, while delays in total developmental time ranged between 7 and 13 days. The lectin had no effect on development of larvae of M. vitrala, when tested through topical artificial diet incorporation assays, except at the extremely high dose of 35% dietary level.

This paper reports the preliminary characterization of seed protein fractions from seven varieties of velvet beans (Mucuna pruriens) grown in Nigeria, using sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE). Three of the most abundant polypeptides, with approximate Mr of 23, 26 and 30 kDa, respectively, were further separated by preparative native-PAGE. N-terminal sequencing revealed the presence of the consensus sequence DDREPV-DT–PL that is also present in the soybean Kunitz-type trypsin inhibitor. The albumin fraction was also shown to contain both trypsin and chymotrypsin inhibitors through enzyme inhibitor assays. Western analysis using antibodies, raised against a representative, 23 kDa polypeptide, indicated that this protein species accumulates exclusively during seed development, suggesting a role in seed storage. Haemagglutination assays using rabbit erythrocytes failed to detect the presence of lectins. The results are discussed within the context of the role of lectins and protease inhibitors in storage and plant defence. The findings are also relevant in view of the toxic and antimetabolic effects of these proteins, which determine the acceptability and adoption of velvet beans as animal and human feed.

Abstract The legume pod-borer Maruca vitrata (Fabricius), [Lepidoptera: Pyralidae] is a major constraint restricting increased cowpea production in tropical Africa and Asia. Since lectins are known to have insecticidal properties against several pests, a survey was undertaken to screen for the effects of 25 lectins from 15 plant families on the development of Maruca pod borer (MPB) larvae. The list included 8 galactose/N-acetylgalactosamine-, 7 mannose-, 5 complex glycan-, 2 sialic acid- and 3, N-acetylglucosamine-specific lectins. Feeding bioassays using artificial diet were carried out at 2% (w/w) topical levels. Although a total of 16 lectins had detrimental effects pertaining either to larval survival, weight, feeding inhibition, pupation, adult emergence and/or fecundity, only the Listera ovata agglutinin (LOA) (Orchidaceae) and Galanthus nivalis (Amaryllidaceae) agglutinin were effective against MPB larvae for all six parameters examined. Larval mortality and feeding inhibition caused by the most active lectin (LOA) was above 60%.

A new galactose-specific lectin was isolated from African yam bean (Sphenostyles stenocarpa Harms) by affinity chromatography on galactose-Sepharose 4B. SDS-PAGE analysis resulted in four polypeptide bands of approximately 27, 29, 32 and 34 kDa, respectively. Based on the analysis of carbohydrate content and native PAGE, it is likely that the Sphenostyles lectin is a tetrameric glycoprotein with M(r) of approximately 122 kDa. N-terminal protein sequencing of purified lectins from four different Sphenostyles accessions shows that the four polypeptides have largely identical amino acid sequences. The sequences contain the conserved consensus sequence F-F-LILG characteristic of legume lectins, as well as Phaseolus vulgaris proteins in the arcelin-alpha-amylase inhibitor gene family. The lectin agglutinates both rabbit and human erythrocytes, but with a preference for blood types A and O. Using Western blotting, the lectin was shown to accumulate rapidly during seed development, but levels dropped slightly as seeds attained maturity. This is the first time a lectin has been purified from the genus Sphenostyles. The new lectin was assigned the abbreviation LECp.SphSte.se.Hga1.