MicroRNAs (miRNAs) are small non-coding RNA molecules essential for growth and development in eukaryotes. In plants, the master gene DICER-LIKE 1 (DCL1) catalyzes the biogenesis of miRNAs by processing double-stranded precursors that give rise to mature miRNAs. We sought to understand the function and evolution of microRNAs using Marchantia polymorpha, a model bryophyte that allows comparative approaches to infer characteristics of the ancestral land plant. We functionally characterized loss-of-function mutants of MpDCL1 a generated by means of CRISPR-Cas9-mediated genomic edition and the miR166/CLASS III HD-ZIP regulatory circuit in Marchantia polymorpha. We report that MpDCL1a is required for the biogenesis of miRNAs and uncovered a central role for miR166/Homeodomain Zipper Class III-regulated auxin synthesis in the specification of cell identity, patterning, meristem function, laminar expansion, and the development of the body in the last common ancestor of the bryophytes and vascular plants. Our findings indicate that DCL1, Class III HD-ZIP, miR166, and auxin functioned in the development of the body of the last common ancestor of extant land plants and provide a novel working framework to interrogate the basic principles of cell specification and patterning in plants.
Adolfo Aguilar-Cruz, E. Flores-Sandoval, Ye Xu et al.· New Phytologist· 0 citations
Monoterpenes (C10) are a large group of specialized metabolites important for plant interactions with the environment. Their biosynthesis is well understood in seed plants, where geranyl diphosphate serves as the canonical substrate, but knowledge of monoterpene biosynthesis outside seed plants remains very limited. Here, we report neryl diphosphate (NPP)-derived monoterpene biosynthesis via a biosynthetic gene cluster in the liverwort Marchantia polymorpha. MpMTPSL2, a microbial-type terpene synthase, converts NPP into α-phellandrene and D-limonene in vitro. CRISPR knockout lines showed reduced production of both monoterpenes, providing direct genetic evidence for its in planta function. MpCPT5, a cis-prenyltransferase (CPT) family member identified through co-expression with MpMTPSL2, was confirmed to encode NPP synthase, as its knockout plants abolished α-phellandrene and D-limonene production. Subcellular localization analyses in protoplasts and stable transgenic plants demonstrated that both MpCPT5 and MpMTPSL2 localize to plastids, co-localizing across all cell types with markedly stronger signals in non-green plastids of oil-body cells. Consistent with this, expression of both genes under their respective promoters was nearly abolished in oil-body-deficient mutants and strongly upregulated in a gain-of-function line for oil-body formation. MpMTPSL2 and MpCPT5 are physically linked through a shared bidirectional promoter that drives their coexpression specific to oil body cells, forming a unique biosynthetic gene cluster whose coordinated expression is maintained by PRC2-mediated H3K27me3 repression. Phylogenetic analysis implies that NPP synthases in M. polymorpha and in flowering plants evolved independently from their respective long-chain CPT ancestors. These findings provide new insights into the mechanisms and evolution of monoterpene biosynthesis in non-seed plants. Significance statement Monoterpenes are a diverse group of specialized metabolites produced widely among land plants, yet our understanding of their biosynthesis outside seed plants remains limited. Here we report that in the liverwort Marchantia polymorpha, the non-canonical substrate neryl diphosphate is used for monoterpene biosynthesis. The functions of the monoterpene synthase gene MpMTPSL2 and the neryl diphosphate synthase gene MpCPT5 were demonstrated through CRISPR knockouts. These two genes are physically linked and share a bidirectional promoter. Promoter assays show both genes function in plastids within oil-body cells, revealing cell-type specificity. These findings shew new light on the mechanisms and evolution of monoterpene biosynthesis in non-seed plants.
Guo Wei, T. Kawaguchi, Facundo Romani et al.· bioRxiv· 0 citations
