Gene trap strategies to unravel and characterize novel biotic-stress inducible genes in plants

Plants, being sedentary in nature constantly encounter various biotic factors such as insects, fungi, bacteria, viruses, nematodes etc. In order to combat them, plants have developed defence mechanisms at anatomical, biochemical, physiological and genetic levels. The expression of genes involved in various biological pathways including signal transduction, phytohormones signalling, osmoregulation, sugar transport, ROS homeostasis, calcium and MAPK pathways, etc., plays pivotal role in imparting resistance to biotic stresses. Therefore, identification and functional characterization of biotic-stress responsive genes are highly imperative to breed biotic stress tolerant cultivars. Gene trap strategies serve as a powerful tool to identify and unravel the biological functions of novel genes and promoters involved in stress tolerance. The candidate gene/promoter flanking the inserted gene trap can be easily cloned using the sequence information of the trap. Various strategies of gene trapping involve T-DNA and transposon based random insertional mutagenesis, transposon based random insertional mutagenesis and activation tagging. To accomplish trapping of target sequence, various vectors have been developed. Recently, gene trap strategies have been successfully imparted to identify and characterize key genes or promoters involved in biotic stress reactions. In the present review, the various gene trap strategies used for identification and cloning of biotic stress responsive genes using DNA vector-based gene traps are discussed.