The Pochonia chlamydosporia Serine Protease Gene vcp1 Is Subject to Regulation by Carbon, Nitrogen and pH: Implications for Nematode Biocontrol

The alkaline serine protease VCP1 of the fungus Pochonia chlamydosporia belongs to a family of subtilisin-like enzymes that are involved in infection of nematode and insect hosts. It is involved early in the infection process, removing the outer proteinaceous vitelline membrane of nematode eggs. Little is known about the regulation of this gene, even though an understanding of how nutrients and other factors affect its expression is critical for ensuring its efficacy as a biocontrol agent. This paper provides new information on the regulation of vcp1 expression. Sequence analysis of the upstream regulatory region of this gene in 30 isolates revealed that it was highly conserved and contained sequence motifs characteristic of genes that are subject to carbon, nitrogen and pH-regulation. Expression studies, monitoring enzyme activity and mRNA, confirmed that these factors affect VCP1 production. As expected, glucose reduced VCP1 expression and for a few hours so did ammonium chloride. Surprisingly, however, by 24 h VCP1 levels were increased in the presence of ammonium chloride for most isolates. Ambient pH also regulated VCP1 expression, with most isolates producing more VCP1 under alkaline conditions. There were some differences in the response of one isolate with a distinctive upstream sequence including a variant regulatory-motif profile. Cryo-scanning electron microscopy studies indicated that the presence of nematode eggs stimulates VCP1 production by P. chlamydosporia, but only where the two are in close contact. Overall, the results indicate that readily-metabolisable carbon sources and unfavourable pH in the rhizosphere/egg-mass environment may compromise nematode parasitism by P. chlamydosporia. However, contrary to previous indications using other nematophagous and entomopathogenic fungi, ammonium nitrate (e.g. from fertilizers) may enhance biocontrol potential in some circumstances

Potential of intercropping for management of some arthropod and nematode pests of leafy vegetables in Kenya

African leafy vegetables (ALVs) play an important role as income and food security crops in many households in Kenya. However, their potential in alleviating poverty and ensuring household food and nutrition security has not been fully exploited. The objectives of this study were to identify some arthropod and nematode pests that infest ALVs and to evaluate the effectiveness of intercropping of susceptible and resistant plants for the management purposes. Three vegetable types: African nightshade, sunn hemp and spider plant were used in determining the efficacy of an intercrop of susceptible and non-susceptible types in reducing arthropod and nematode pest effect. The treatments in the field experiment consisted of different intercrop designs and a sole crop design as control while data was taken based on five different variables. Crops in the field were infested with arthropod pests and eight different species were enumerated. The same row and hill intercropping designs were the most effective in reducing the effect of arthropod and nematode pests compared to the control plots. Spider plant and African nightshade intercrops recorded the least arthropod pest damage, higher fresh and dry shoot yields and differed significantly (P≤0.05) to African nightshade planted as a sole crop. A similar trend was observed when the experiment was repeated with a sunn hemp and African nightshade intercrop. It is concluded from this study that intercropping of different crops can be integrated with other methods to provide an easily adaptable technology to apply for effective management of arthropod and nematode pests with low external inputs

The nutrition transition and indicators of child malnutrition

We analyze how the nutrition transition affects child malnutrition in developing countries. It is often assumed that the nutrition transition affects child weight but not child growth, which could be one reason why child underweight decreases faster than child stunting. But these effects have hardly been analyzed empirically. Our cross-country panel regressions show that the nutrition transition reduces child underweight, while no consistent effect on child overweight is found. Against common views, our results also suggest that the nutrition transition reduces child stunting. Further research is required to confirm these findings