Investigation of benzylisoquinoline alkaloid biosynthetic pathway and its transcriptional regulation in lotus

Lotus predominantly accumulates benzylisoquinoline alkaloids(BIAs),but their biosynthesis and regulation remain unclear.Here,we investigated structural and regulatory genes involved in BIA accumulation in lotus.Two clustered CYP80 genes were identified to be responsible for the biosynthesis of bis-BIAs and aporphine-type BIAs,respectively,and their tissue-specific expression causes divergence in alkaloid component between leaf and embryo.In contrast with the common(S)-reticuline precursor for most BIAs,aporphine alkaloids in lotus leaf may result from the(S)-N-methylcoclaurine precursor.Structural diversity of BIA alkaloids in the leaf is attributed to enzymatic modifications,including intramolecular C–C phenol coupling on ring A and methylation and demethylation at certain positions.Additionally,most BIA biosynthetic pathway genes show higher levels of expression in the leaf of high-BIA cultivar compared with low-BIA cultivar,suggesting transcriptional regulation of BIA accumulation in lotus.Five transcription factors,including three MYBs,one ethylene-responsive factor,and one basic helix–loop–helix(bHLH),were identified to be candidate regulators of BIA biosynthesis in lotus.Our study reveals a BIA biosynthetic pathway and its transcriptional regulation in lotus,which will enable a deeper understanding of BIA biosynthesis in plants.

莲的离体快速繁殖技术

以莲(Nelumbonucifera)授粉后18天的莲子胚芽为外植体,通过初代培养、继代培养和炼苗移栽,建立了莲离体快速繁殖体系。结果表明,将胚芽外植体诱导出无菌苗的最适初代培养基为MS固体培养基添加0.5 mg·L^(-1) 6-BA、0.5 mg·L^(-1)NAA、30 g·L^(-1)蔗糖、0.5 g·L^(-1)活性炭和0.8 g·L^(-1)琼脂,培养60天诱导率高于85%,其中秋红阳走茎节数最多(3.9)。最佳继代培养基为将初代培养基中的蔗糖浓度提高到80g·L^(-1),走茎采用两节一切的分苗切法,无菌苗可50天继代1次,最多可继代6次,不同品种的增殖系数介于4.0–6.7之间,以秋红阳最高(6.7)。于5–7月将生根的走茎无菌苗移栽入泥炭:塘泥=1:2(v/v)的混合基质中进行培养,成活率均大于83.9%。采用上述快繁技术,理论上1个莲子胚芽经过近1年可繁殖出种苗1 465株。该研究建立了莲的离体快繁技术体系,可为莲种苗的规模化生产提供技术支持。