The role of cuscutain-propeptide inhibitor in haustoria parasitism and enhanced resistance to dodder in transgenic alfalfa expressing this propeptide
2018
Amini, Massoume | Saify Nabiabad, Haidar | Deljou, Ali
Cuscutain is a cysteine protease produced by dodder (the most important weeds of alfalfa) that is essential for the development and penetration of the haustoria in host. The propeptide subunit of cuscutain has a specific inhibitory function and inhibits the enzymatic activity of the cuscutain. In this study, we introduced the gene encoding the propeptide segment of the cuscutain (signal peptide-less inhibitor) into alfalfa and investigated its roles in parasitism and the alfalfa resistance to C. reflexa. Results demonstrated that cuscutain is mainly expressed in haustoria and the expression of propeptide in transgenic alfalfa plants effectively inhibited cuscutain enzyme activity and consequently interrupted haustoria development at the pathogenic stage. Digitate cells of haustoria could not differentiate into the xylem and phloem hyphae in dodder grown on transgenic alfalfa. Dodder development on transgenic alfalfa lines showed an overall reduction in fecundity and vigor due to imperfect attachment of haustoria. Morphology, nodule development and biomass of transgenic plants indicate that the inhibitory transgene exhibits exquisite specificity for cuscutain enzyme and by expression of the inhibitor in transgenic plants, there was no obvious adverse effect on them. The increased development and growth of dodder-challenged alfalfa transgenic plants compared to controls, showed the efficacy of propeptide in dodder control.
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