In nature Citrus tristeza virus (CTV). genus Closterovirus. infects only the phloem cells of species of Citrus and related genera. Finding that the CTV T36 strain replicated in Nicotiana benthamiana (NB) protoplasts and produced normal virions allowed development of the first genetic system based on protoplast transfection with RNA transcribed from a full-genome cDNA clone. https://foldlyers.shop/product-category/micro-switches/