Transcriptome analysis provides insights into the non-methylated lignin synthesis in Paphiopedilum armeniacum seed

• DOI: 10.21203/rs.2.13152/v3
• Publication Date: 2020-06-11T18:40:55Z
• Authors: lin fang; Xin Xu; Ji Li; Feng Zheng; Mingzhi Li; Jingwei Yan; Yuan Li; Xinhua Zhang; Lin Li; Guohua Ma; Aying Zhang; Fubin Lv; Kunlin Wu; Songjun Zeng
• Keywords: 0301 basic medicine; 2. Zero hunger; 0303 health sciences; Gene Expression Profiling; Germination; QH426-470; 15. Life on land; Lignin; Paphiopedilum armeniacum; 03 medical and health sciences; Gene Expression Regulation, Plant; Seeds; Genetics; Transcriptome analysis; Orchidaceae; Transcriptome; TP248.13-248.65; Biotechnology; Research Article

Abstract Backgrounds: Paphiopedilum is an important genus of the orchid family Orchidaceae and has high horticultural value. The wild populations are under threat of extinction because of overcollection and habitat destruction. Mature seeds of most Paphiopedilum species are difficult to germinate, which severely restricts their germplasm conservation and commercial production. The factors inhibiting germination are largely unknown.Results: In this study, large amounts of non-methylated lignin accumulated during seed maturation of Paphiopedilum armeniacum (P. armeniacum), which negatively correlates with the germination rate. The transcriptome profiles of P. armeniacum seed at different development stages were compared to explore the molecular clues for non-methylated lignin synthesis. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that a large number of genes associated with phenylpropanoid biosynthesis and phenylalanine metabolism during seed maturation were differentially expressed. Several key genes in the lignin biosynthetic pathway displayed different expression patterns during the lignification process. PAL, 4CL, HCT, and CSE upregulation was associated with C and H lignin accumulation. The expression of CCoAOMT, F5H, and COMT were maintained at a low level or down-regulated to inhibit the conversion to the typical G and S lignin. Quantitative real-time RT-PCR analysis confirmed the altered expression levels of these genes in seeds and vegetative tissues. Conclusions: This work demonstrated the plasticity of natural lignin polymer assembly in seed and provided a better understanding of the molecular mechanism of seed-specific lignification process.