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Sporopollenin is often said to be one of the toughest biopolymers known to man. The shift in dormancy cell wall deposition from around the diploid zygotes of charophycean algae to sporopollenin around the haploid spores of land plants essentially imparted onto land plants the gift of passive motility, a key acquisition that contributed to their vast and successful colonization across terrestrial habitats. 1 , 2 A putative transcription factor controlling the land plant mode of sporopollenin deposition is the subclass II bHLHs, which are conserved and novel to land plants, with mutants of genes in angiosperms and mosses divulging roles relating to tapetum degeneration and spore development. 3 , 4 , 5 , 6 , 7 We demonstrate that a subclass II bHLH gene, MpbHLH37, regulates sporopollenin biosynthesis and deposition in the model liverwort Marchantia polymorpha. Mpbhlh37 sporophytes show a striking loss of secondary wall deposits of the capsule wall, the elaters, and the spore exine, all while maintaining spore viability, identifying MpbHLH37 as a master regulator of secondary wall deposits of the sporophyte. Localization of MpbHLH37 to the capsule wall and elaters of the sporophyte directly designates these tissue types as a bona fide tapetum in liverworts, giving support to the notion that the presence of a tapetum is an ancestral land plant trait. Finally, as early land plant spore walls exhibit evidence of tapetal deposition, 8 , 9 , 10 , 11 , 12 a tapetal capsule wall could have provided these plants with a developmental mechanism for sporopollenin deposition., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Land plants are celebrated as one of the three great instances of complex multicellularity, but new phylogenomic and phenotypic analyses are revealing deep evolutionary roots of multicellularity among algal relatives, prompting questions about the causal basis of this major evolutionary transition., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Pattern-recognition receptor (PRR)-triggered immunity (PTI) wards off a wide range of pathogenic microbes, playing a pivotal role in angiosperms. The model liverwort Marchantia polymorpha triggers defense-related gene expression upon sensing components of bacterial and fungal extracts, suggesting the existence of PTI in this plant model. However, the molecular components of the putative PTI in M. polymorpha and the significance of PTI in bryophytes have not yet been described. We here show that M. polymorpha has four lysin motif (LysM)-domain-containing receptor homologs, two of which, LysM-receptor-like kinase (LYK) MpLYK1 and LYK-related (LYR) MpLYR, are responsible for sensing chitin and peptidoglycan fragments, triggering a series of characteristic immune responses. Comprehensive phosphoproteomic analysis of M. polymorpha in response to chitin treatment identified regulatory proteins that potentially shape LysM-mediated PTI. The identified proteins included homologs of well-described PTI components in angiosperms as well as proteins whose roles in PTI are not yet determined, including the blue-light receptor phototropin MpPHOT. We revealed that MpPHOT is required for negative feedback of defense-related gene expression during PTI. Taken together, this study outlines the basic framework of LysM-mediated PTI in M. polymorpha and highlights conserved elements and new aspects of pattern-triggered immunity in land plants., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

All plant cells are surrounded by a cell wall that provides cohesion, protection, and a means of directional growth to plants. Cellulose microfibrils contribute the main biomechanical scaffold for most of these walls. The biosynthesis of cellulose, which typically is the most prominent constituent of the cell wall and therefore Earth's most abundant biopolymer, is finely attuned to developmental and environmental cues. Our understanding of the machinery that catalyzes and regulates cellulose biosynthesis has substantially improved due to recent technological advances in, for example, structural biology and microscopy. Here, we provide a comprehensive overview of the structure, function, and regulation of the cellulose synthesis machinery and its regulatory interactors. We aim to highlight important knowledge gaps in the field, and outline emerging approaches that promise a means to close those gaps., (Copyright © 2022 The Author. Published by Elsevier Inc. All rights reserved.)

The Zygnematophyceae is the sister clade to the land plants, but their biology remains mysterious. In a new study, a resolved phylogeny and a scenario for the evolution of multicellularity in that clade are proposed., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Studying the evolution of metabolism is technically challenging. A new study combining in silico metabolic maps and phylogenomics allows reconstructing the diversification of plant metabolism across one billion years of evolution., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Two new studies that consider the timing of origin of angiosperms are poles apart in their estimates. However, their partisan molecular and palaeontological perspectives may hold the key to establishing a unified evolutionary timescale for flowering plants., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Biochemical defenses against oomycete infection were already present in early diverging plant lineages, suggesting parallel selection for phenylpropanoid metabolites., (Copyright © 2019. Published by Elsevier Ltd.)

Oriented cell divisions correlate with body axis formation and elaboration of form. Probing a developmental switch from 2D to 3D growth in moss, recent studies have identified the plant meristem-associated CLAVATA signaling system as a crucial regulator of division orientation and a potential evolutionary innovation enabling elaborate land plant forms., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The key structures and functions of land plants are most often studied in flowering plant models. However, the evolution of these traits (character states) is often difficult to infer, because we lack an accurate phylogenetic frame of reference. The potential branching order of the earliest land plants has now been further condensed, narrowing down potential reference frameworks for comparative studies., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The genome of the liverwort Marchantia polymorpha is an important step toward development of a new plant model system (Bowman et al., 2017). Liverworts may be the sister taxon to all other land plants, and the genome shows features that illuminate the ancestor of all land plants and give insights into how plant systems function and evolved., (Copyright © 2017 Elsevier Inc. All rights reserved.)

A long-standing question in biology is how a group of primordial cells can give rise to complex organs. A new study finds that, in an ancient land plant, growth rate variation patterned by meristematic cells primarily determines shape., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The genetic and molecular basis of the developmental programs underlying adaptive morphological changes is largely unknown. A new study reveals an ancient gene that has been instrumental for the generation of morphological diversity and adaptation in land plants., (Copyright © 2016 Elsevier Ltd. All rights reserved.)