Mutation in shoot-to-root mobile transcription factor, ELONGATED HYPOCOTYL 5, leads to low nicotine levels in tobacco

Abstract

Tobacco remains one of the most commercially important crops due to the parasympathomimetic alkaloid nicotine used in cigarettes. Most genes involved in nicotine biosynthesis are expressed in root tissues; however, their light-dependent regulation has not been studied. We identified the ELONGATED HYPOCOTYL 5 homolog, NtHY5, from Nicotiana tabacum and demonstrated its role in nicotine biosynthesis. We report the development of CRISPR/Cas9-based mutant plants, NtHY5CR, and show down-regulation of the nicotine biosynthetic pathway, whereas NtHY5 overexpression (NtHY5OX) plants show the opposite effect. Grafting experiments using wild type, NtHY5CR, and NtHY5OX indicated that NtHY5 moves from shoot-to-root to regulate nicotine biosynthesis in the root tissue. We conclude that shoot HY5, directly or through enhancing expression of the HY5 in the root, promotes nicotine biosynthesis. The CRISPR/Cas9-based mutants developed, in this study; with low nicotine accumulation in leaves could help people to overcome their nicotine addiction and the risk of death from tobacco use.