Phaeocerosperpusillus var. scabrellus (Notothyladaceae, Anthocerotophyta), a new taxon from northern Thailand.

A new variety of hornwort from northern Thailand, Phaeocerosperpusillusvar.scabrellus is described based on morphological characters and molecular phylogenetic analyses. In this study, phylogenetic analyses supported that the new variety is closely related to P.perpusillusvar.perpusillus. Morphologically, it is distinguished from the autonimic variety in nearly smooth spores under light microscope. A taxonomic description, illustrations, and light and scanning electron micrographs are provided. In addition, the new variety is assessed as Endangered (EN), demonstrating its rarity by being currently known from only three subpopulations.

Biolistics-mediated transformation of hornworts and its application to study pyrenoid protein localization.

Hornworts are a deeply diverged lineage of bryophytes that are sister to mosses and liverworts. Hornworts have an array of unique features that can be leveraged to illuminate not only the early evolution of land plants, but also alternative paths for nitrogen and carbon assimilation via cyanobacterial symbiosis and a pyrenoid-based CO2-concentrating mechanism (CCM), respectively. Despite this, hornworts are one of the few plant lineages with limited available genetic tools. Here we report an efficient biolistics method for generating transient-expression and stable transgenic lines in the model hornwort, Anthoceros agrestis. An average of 569 (± 268) cells showed transient expression per bombardment, with green fluorescent protein expression observed within 48-72 hours. A total of 81 stably transformed lines were recovered across three separate experiments, averaging six lines per bombardment. We followed the same method to transiently transform nine additional hornwort species, and obtained stable transformants from one. This method was further used to verify the localization of Rubisco and Rubisco activase in pyrenoids, which are central proteins for CCM function. Together, our biolistics approach offers key advantages over existing methods as it enables rapid transient expression and can be applied to widely diverse hornwort species.

Convergent evolution of fern nectaries facilitated independent recruitment of ant-bodyguards from flowering plants.

Plant-herbivore interactions reciprocally influence species' evolutionary trajectories. These interactions have led to many physical and chemical defenses across the plant kingdom. Some plants have even evolved indirect defense strategies to outsource their protection to ant bodyguards by bribing them with a sugary reward (nectar). Identifying the evolutionary processes underpinning these indirect defenses provide insight into the evolution of plant-animal interactions. Using a cross-kingdom, phylogenetic approach, we examined the convergent evolution of ant-guarding nectaries across ferns and flowering plants. Here, we discover that nectaries originated in ferns and flowering plants concurrently during the Cretaceous, coinciding with the rise of plant associations in ants. While nectaries in flowering plants evolved steadily through time, ferns showed a pronounced lag of nearly 100 My between their origin and subsequent diversification in the Cenozoic. Importantly, we find that as ferns transitioned from the forest floor into the canopy, they secondarily recruited ant bodyguards from existing ant-angiosperm relationships.

Genomes of multicellular algal sisters to land plants illuminate signaling network evolution.

Zygnematophyceae are the algal sisters of land plants. Here we sequenced four genomes of filamentous Zygnematophyceae, including chromosome-scale assemblies for three strains of Zygnema circumcarinatum. We inferred traits in the ancestor of Zygnematophyceae and land plants that might have ushered in the conquest of land by plants: expanded genes for signaling cascades, environmental response, and multicellular growth. Zygnematophyceae and land plants share all the major enzymes for cell wall synthesis and remodifications, and gene gains shaped this toolkit. Co-expression network analyses uncover gene cohorts that unite environmental signaling with multicellular developmental programs. Our data shed light on a molecular chassis that balances environmental response and growth modulation across more than 600 million years of streptophyte evolution.

Extraordinary preservation of gene collinearity over three hundred million years revealed in homosporous lycophytes.

Homosporous lycophytes (Lycopodiaceae) are a deeply diverged lineage in the plant tree of life, having split from heterosporous lycophytes (Selaginella and Isoetes) ~400 Mya. Compared to the heterosporous lineage, Lycopodiaceae has markedly larger genome sizes and remains the last major plant clade for which no chromosome-level assembly has been available. Here, we present chromosomal genome assemblies for two homosporous lycophyte species, the allotetraploid Huperzia asiatica and the diploid Diphasiastrum complanatum. Remarkably, despite that the two species diverged ~350 Mya, around 30% of the genes are still in syntenic blocks. Furthermore, both genomes had undergone independent whole genome duplications, and the resulting intragenomic syntenies have likewise been preserved relatively well. Such slow genome evolution over deep time is in stark contrast to heterosporous lycophytes and is correlated with a decelerated rate of nucleotide substitution. Together, the genomes of H. asiatica and D. complanatum not only fill a crucial gap in the plant genomic landscape but also highlight a potentially meaningful genomic contrast between homosporous and heterosporous species.