Analysis of Expresion Patterns of zmrcp1 and camv35s in Plantains in Association with Nematodes Infection
Onyango, Stephen Odhiambo
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Plantains are among staple foods in Africa. Worldwide, Musa spp. have an annual production of 88 million tonnes. Nematodes cause significant annual yield losses to these crops. The losses are estimated at about 20% worldwide. The most disastrous nematodes are Radopholus similis and Platylenchus goodeyi. Genetic improvement of the crops by conventional breeding has proved to be laborious and time consuming. Transgenic technology can offer sustainable solutions to the problem of controlling plant parasitic nematodes. To date, only constitutive heterologous promoters such as maize ubiquitin 1, rice actin 1, viral promoter (CaMV35S) have been used for the production of transgenic banana plants. This study defined the potential of Zea mays root cap specific promoter-1 (ZmRCP1) to drive biosynthesis of an anti-nematodes effector in plantain roots. Transgenic plants used in this study were regenerated from embryogenic cell suspension (ECS) of Gonja manjaya transformed by Agrobacterium tumefaciens strain EHA105 harboring the binary vectors pBI121 and pBI-ZmRCP:GUS. The study was designed to establish the difference in expression patterns of gusA gene under Cauliflower Mosaic Virus 35S (CaMV35S) constitutive promoter and ZmRCP1 and to assess the impact of R.similis infection on plantains at various stages of growth. To achieve the objectives, the study involved confirmation of the presence of gusA gene in plantain genomic DNA, inoculation of the plantains with nematodes and analysis of gusA gene expression pattern in the infected plants. Nematodes infection was achieved with R. similis. PCR amplicons were observed in all transgenic lines when DNA amplification was done using gusA specific primers. A histochemical GUS assay showed root cap expression of gusA in RCP1 lines. R.similis infection had no influence on ZmRCP1 expression pattern. The effect of R. similis infection on total leaf area (TLA) and total plant biomass (TPB) during infection period was analyzed. Consequently, a two-tailed t-test performed at 95% confidence level revealed a significant difference (P<0.05) between TLA and TPB of infected and uninfected plants. Infected lines showed lower TLA than uninfected lines. Nematodes infection reduced TPB of infected clones. The decline in TLA and TPB shows minimal or negligible natural resistance from G.manjaya against R. similis. As nematode population increased in roots, gusA expression at the root tip of RCP1 plants intensified. ZmRCP1 restricts gene expression at the root cap hence making it favourable for use in delivering a chemodisruptive peptide that can be released into rhizosphere with the root exudates. A lethal peptide can be used to achieve a complete resistance status in Musa spp.