Medina R., M. Johnson, Y. Liu, N. Wilding, T. Hedderson, N. Wickett & B. Goffinet. 2018. Evolutionary dynamism in bryophytes: Phylogenomic inferences confirm rapid radiation in the family Funariaceae. Molecular Phylogenetics and Evolution 120: 240–247. pdf
Abstract: Rapid diversifications of plants are primarily documented and studied in angiosperms, which are perceived as evolutionarily dynamic. Recent studies have, however, revealed that bryophytes have also undergone periods of rapid radiation. The speciose family Funariaceae, including the model taxon Physcomitrella patens, is one such lineage. Here, we infer relationships among major lineages within the Entosthodon-Physcomitrium complex from virtually complete organellar exomes (i.e., 123 genes) obtained through high throughput sequencing of genomic libraries enriched in these loci via targeted locus capture. Based on these extensive exonic data we (1) reconstructed a robust backbone topology of the Funariaceae, (2) confirmed the monophyly of Funaria and the polyphyly of Entosthodon, Physcomitrella, and Physcomitrium, and (3) argue for the occurrence of a rapid radiation within the Entosthodon-Physcomitrium complex that began 28 mya and gave rise more than half of the species diversity of the family. This diversification may have been triggered by a whole genome duplication and coincides with global Eocene cooling that continued through the Oligocene and Miocene. The Funariaceae join a growing list of bryophyte lineages whose history is marked by at least one burst of diversification, and our study thereby strengthens the view that bryophytes are evolutionarily dynamic lineages and that patterns and processes characterizing the evolution of angiosperms may be universal among land plants.
Budke J.M. & B. Goffinet. 2016. Comparative cuticle development in morphologically divergent mosses of the Funariaceae. Frontiers in Plant Sciences 7: 832. pdf (open access) Google Scholar
Abstract:The calyptra is a maternal structure that protects the sporophyte offspring from dehydration, and positively impacts sporophyte survival and fitness in mosses. We explore the relationship between cuticle protection and sporophyte height as a proxy for dehydration stress in Funariaceae species with sporophytes across a range of sizes. Calyptrae and sporophytes from four species were collected from laboratory-grown populations at two developmental stages. Tissues were embedded, sectioned, and examined using transmission electron microscopy. Cuticle thickness was measured from three epidermal cells per organ for each individual and compared statistically. All four species have cuticles consisting of a cuticle proper and a cuticular layer on the calyptra and sporophyte at both developmental stages. Across species, shorter sporophytes are associated with smaller calyptra and thinner calyptra cuticles, whereas taller sporophytes are associated with larger calyptra and thicker calyptra cuticles. Independent of size, young sporophytes have a thin cuticle that thickens later during development, while calyptrae have a mature cuticle produced early during development that persists throughout development. This study adds to our knowledge of maternal effects influencing offspring survival in plants. Released from the pressures to invest in protection for their sporophyte offspring, maternal resources can be allocated to other processes that support sporophyte reproductive success. Using a comparative developmental framework enables us to broaden our understanding of cuticle development across species and provides structural evidence supporting the waterproofing role of the moss calyptra.
Magdy M., O. Werner, S.F. McDaniel, B. Goffinet & R.M. Ros. 2016. A genomic scanning using AFLP to detect loci under selection in Funaria hygrometrica Hedw. along a climatic gradient in the Sierra Nevada mountains (Spain). Plant Biology 18: 280–288. pdf Google Scholar
The common cord moss Funaria hygrometrica has a worldwide distribution and thrives in a wide variety of environments. Here, we studied the genetic diversity in F. hygrometrica along an abiotic gradient in the Mediterranean high mountain of Sierra Nevada (Spain) using a genome scan method. Eighty-four samples from 17 locations from 24 to 2700 m were fingerprinted based on their amplified fragment length polymorphism (AFLP) banding pattern. Using PCA and Bayesian inference we found that the genetic diversity was structured in three or four clusters, respectively. Using a genome scan method we identified 13 outlier loci, which showed a signature of positive selection. Partial Mantel tests were performed between the Euclidean distance matrices of geographic and climatic variables, versus the pair-wise genetic distance of the AFLP dataset and AFLP-positive outliers dataset. AFLP-positive outlier data were significantly correlated with the gradient of the climatic variables, suggesting adaptive variation among populations of F. hygrometrica along the Sierra Nevada Mountains. We highlight the additional analyses necessary to identify the nature of these loci, and their biological role in the adaptation process.
Budke, J. M., B. Goffinet & C. S. Jones. 2013. Dehydration protection provided by a maternal cuticle improves offspring ﬁtness in the moss Funaria hygrometrica. Annals of Botany 111: 781–789. pdf Google Scholar
Abstract:In bryophytes the sporophyte offspring are in contact with, nourished from, and partially surrounded by the maternal gametophyte throughout their lifespan. During early development, the moss sporophyte is covered by the calyptra, a cap of maternal gametophyte tissue that has a multilayered cuticle. In this study the effects on sporophyte offspring fitness of removing the maternal calyptra cuticle, in combination with dehydration stress, is experimentally determined. Using the moss Funaria hygrometrica, calyptra cuticle waxes were removed by chemical extraction and individuals were exposed to a short-term dehydration event. Sporophytes were returned to high humidity to complete development and then aspects of sporophyte survival, development, functional morphology, and reproductive output were measured. It was found that removal of calyptra cuticle under low humidity results in significant negative impacts to moss sporophyte fitness, resulting in decreased survival, increased tissue damage, incomplete sporophyte development, more peristome malformations, and decreased reproductive output. This study represents the strongest evidence to date that the structure of the calyptra cuticle functions in dehydration protection of the immature moss sporophyte. The investment in a maternal calyptra with a multilayered cuticle increases offspring fitness and provides a functional explanation for calyptra retention across mosses. The moss calyptra may represent the earliest occurance of maternal protection via structural provisioning of a cuticle in green plants.
Liu Y., L.L. Forrest, J. Bainard, J.M Budke & B. Goffinet. 2013. Organellar genome, nuclear ribosomal DNA repeat unit and microsatellites isolated from a small scale of 454 GS FLX sequencing on two mosses. Molecular Phylogenetics and Evolution 66: 1089–1094. pdf Google Scholar
Abstract:Recent innovations in high-throughput DNA sequencing methodology (next generation sequencing technologies [NGS]) allow for the generation of large amounts of high quality data that may be particularly critical for resolving ambiguous relationships such as those resulting from rapid radiations. Application of NGS technology to bryology is limited to assembling entire nuclear or organellar genomes of selected exemplars of major lineages (e.g., classes). Here we outline how organellar genomes and the entire nuclear ribosomal DNA repeat can be obtained from minimal amounts of moss tissue via small-scale 454 GS FLX sequencing. We sampled two Funariaceae species, Funaria hygrometrica and Entosthodon obtusus, and assembled nearly complete organellar genomes and the whole nuclear ribosomal DNA repeat unit (18S-ITS1-5.8S-ITS2-26S-IGS1-5S-IGS2) for both taxa. Sequence data from these species were compared to sequences from another Funariaceae species, Physcomitrella patens, revealing low overall degrees of divergence of the organellar genomes and nrDNA genes with substitutions spread rather evenly across their length, and high divergence within the external spacers of the nrDNA repeat. Furthermore, we detected numerous microsatellites among the 454 assemblies. This study demonstrates that NGS methodology can be applied to mosses to target large genomic regions and identify microsatellites.
Liu Y., N.L. Moskwa & B. Goffinet.2012. Development of eight mitochondrial markers for Funariaceae (Musci) and the amplification success in other mosses. American Journal of Botany e62–e65. (doi: 10.3732/ajb.1100402; pdf Google Scholar
Abstract: In comparison to the wide use of chloroplast markers, few mitochondrial markers are available for phylogenetic studies in bryophytes. We investigated the phylogenetic suitability of several mtDNA markers within the Funariaceae and across mosses. By comparing mitochondrial genomes of two mosses, eight regions with higher substitution rates were identifi ed and sequenced for three species in the Funariaceae and one outgroup taxon. Variations in the substitution rate of these new loci were compared to previously used markers. Thirty-four samples representing all major moss lineages were targeted to assess the universality of the newly designed primers. The new markers provided similar or more sequence variations in Funariaceae compared to previously developed mtDNA markers. Five out of eight loci were amplifi ed in 70% of other taxa, indicating that these markers may be suitable for phylogenetic studies in other moss lineages.
Budke J.M., B. Goffinet & C.S. Jones. 2012. The cuticle on the calyptra matures before the sporophyte cuticle in the moss Funaria hygrometrica. American Journal of Botany99: 14–22. (doi: 10.3732/ajb.1100311; pdf Google Scholar
Abstract: In vascular plants, leaf primordia prevent desiccation of the shoot apical meristem. Lacking leaves, the undifferentiated moss sporophyte apex is covered by the calyptra, a cap of maternal gametophyte tissue that is hypothesized to function in desiccation protection. Herein, we compare cuticle development on the calyptra and sporophyte to assess the calyptra ’ s potential to protect the sporophyte from desiccation. As the fi rst comprehensive study of moss sporophyte cuticle development, this research broadens our perspectives on cuticle development and evolution across embryophytes. Calyptrae and sporophytes at nine developmental stages were collected from a laboratory-grown population of the moss Funaria hygrometrica . Tissues were embedded, sectioned, then examined using transmission electron microscopy. Epidermal cells were measured for thickness of the cuticle layers, cell wall thickness, and lumen size. The calyptra cuticle develops precociously and reaches maturity before the sporophyte cuticle. Calyptrae are covered by a four-layered cuticle at all stages, whereas sporophyte cuticle maturation is delayed until sporangium formation. The development and thickening of the sporophyte cuticle occurs in an acropetal wave. A multilayered calyptra cuticle at the earliest developmental stages is consistent with its ability to protect the immature sporophyte from desiccation. Young sporophytes lack a complex cuticle and thus may require protection, whereas in older sporophytes a mature cuticle develops. The moss calyptra is not a vestigial structure, but rather the calyptra ’ s role in preventing desiccation offers a functional explanation for calyptra retention during the 450 Myr of moss evolution.
Liu Y., J.M. Budke & B. Goffinet. 2012. Phylogenetic inference rejects sporophyte based classification of the Funariaceae (Bryophyta): rapid radiation suggests rampant homoplasy in sporophyte evolution. Molecular Phylogenetics and Evolution 62: 130–145.pdf Google Scholar
Abstract:The moss family Funariaceae, which includes the model systems Funaria hygrometrica and Physcomitrella patens, comprises 15 genera, of which three accommodate approximately 95% of the 250–400 species. Generic concepts are drawn primarily from patterns in the diversity of morphological complexity of the sporophyte. Phylogenetic inferences from ten loci sampled across the three genomic compartments yield a hypothesis that is incompatible with the current circumscription of two of the speciose genera of the Funariaceae. The single clade, comprising exemplars of Funaria with a compound annulus, is congruent with the systematic concept proposed by Fife (1985). By contrast, Entosthodon and Physcomitrium are resolved as polyphyletic entities, and even the three species of Physcomitrella are confirmed to have diverged from distinct ancestors. Although the backbone relationships within the core clade of the Funariaceae remain unresolved, the polyphyly of these genera withstands alternative hypothesis testing. Consequently, the sporophytic characters that define these lineages are clearly homoplasious suggesting that selective pressures (or their relaxation) are in fact driving the diversification rather than the conservation of sporophytic architecture in the Funariaceae.
Budke J.M., B. Goffinet & C.S. Jones. 2011.A hundred year old question: is the moss calyptra covered by a cuticle? A case study of Funaria hygrometrica. Annals of Botany 107: 1279–1286. (doi: 10.1093/aob/mcr079). pdf Google Scholar
Abstract: The maternal gametophytic calyptra is critical for moss sporophyte development and ultimately sporogenesis. The calyptra has been predicted to protect the sporophyte apex, including the undifferentiated sporogenous region and seta meristem, from desiccation. We investigate the hypothesis that this waterproofing ability is due to a waxy cuticle. The idea that moss calyptrae are covered by a cuticle has been present in the literature forovera century, but, until now, neither the presence nor the absence of a cuticle has been documented for any calyptra. The epidermis of the calyptra, leafy gametophyte and sporophyte sporangia of the moss Funaria hygrometrica were examined using scanning and transmission electron microscopy. Thicknesses of individual cuticle layers were quantified and compared statistically. The immunochemistry antibody (LM19) specific for pectins was used to locate cell wall material within the cuticle. A multi-layered cuticle is present on the calyptra of F. hygrometrica, including layers analogous to the cuticular layer, cell wall projections, electron-lucent and electron-dense cuticle proper observed in vascular plants. The calyptra rostrum has a cuticle that is significantly thicker than the other tissues examined and differs by specialized thickenings of the cuticular layer (cuticular pegs) at the regions of the anticlinal cell walls. This is the first documentation of cuticular pegs in a moss. The calyptra and its associated cuticle represent a unique form of maternal care in embryophytes. This organ has the potential to play a critical role in preventing desiccation of immature sporophytes and thereby may have been essential for the evolution of the moss sporophyte.