Expression of an Insecticidal Protein under Phloem Specific Promoter in Cotton Plants to Control Whitefly

Whitefly the Bemisia tabaci is a phloem sap-sucking hemipteran pest that causes enormous damage to many crop plants, particularly cotton. Bt endotoxins which successfully controlled the chewing pest proved to be mostly ineffective against the whiteflies and many other hemipteran pests. In the past few years, some insecticidal proteins showed significant toxicity against the whiteflies such as Hvt, lectin, and TMA12. In this study, transgenic cotton lines expressing plant-derived insecticidal protein TMA12 under constitutive promoter (2X35S derived from Cauliflower mosaic virus -CaMV) and a phloem-specific promoter (Nuclear shuttle protein-NSP derived from Banana bunchy top virus- BBTV) were developed to compare their efficacy against the whiteflies. Before developing cotton transgenic lines, tobacco transgenic plants were also developed to get preliminary results about the efficacy of the transgene. After molecular characterization, cotton transgenic lines were evaluated for resistance against whitefly in the contained environment. Whitefly survival and fecundity were calculated for each transgenic line. Bioassay data proved the effectiveness of insecticidal protein against whiteflies. These results also concluded that the NSP promoter is potentially an effective strategy against B. tabaci but still its efficiency is not equal to the 2X35S promoter. The use of a phloem-specific promoter has advantages over the constitutive promoter like tissue-specific expression saves the molecular resources of the plant cells and is less prone to biosafety concerns. In the future, more phloem-specific promoters can be explored for enhanced effectivity against B. tabaci .