Comparative analyses of eight complete plastid genomes of two hemiparasitic Cassytha vines in the family Lauraceae.

Cassytha is the sole genus of hemiparasitic vines (ca. 20 spp.) belonging to the Cassytheae tribe of the Lauraceae family. It is extensively distributed in tropical and subtropical regions. In this study, we determined the complete plastid genome sequences of C. filiformis and C. larsenii, which do not possess the typical quadripartite structure. The length of C. filiformis plastomes ranged from 114,215 to 114,618 bp, whereas that of C. larsenii plastomes ranged from 114,900 to 114,988 bp. Comparative genomic analysis revealed 1,013 mutation sites, four large intragenomic deletions, and five highly variable regions in the eight plastome sequences. Phylogenetic analyses based on 61 complete plastomes of Laurales species, 19 ITS sequences, and trnK barcodes from 91 individuals of Cassytha spp. confirmed a non-basal group comprising individuals of C. filiformis, C. larsenii, and C. pubescens in the family Lauraceae and proposed a sister relationship between C. filiformis and C. larsenii. Further morphological comparisons indicated that the presence or absence of hairs on the haustoria and the shape or size of fruits were useful traits for differentiating C. filiformis and C. larsenii.

Structural Profiling of Xyloglucans from Food Plants by High-Performance Anion-Exchange Chromatography with Parallel Pulsed Amperometric and Mass Spectrometric Detection.

Xyloglucans are the dominant hemicelluloses in the primary cell wall of dicotyledonous plants, fulfilling numerous functions. However, routine methods of cell wall analytical chemistry such as methylation analysis are time-consuming and often not adequate to capture the structural diversity of xyloglucans. Here, a xyloglucan profiling method based on the enzymatic release of xyloglucan oligosaccharides by a xyloglucan-specific endo-ß-(1→4)-glucanase and subsequent analysis of these oligosaccharides by high-performance anion-exchange chromatography (HPAEC) with parallel pulsed amperometric and mass spectrometric detection was developed. For this purpose, a set of 23 authentic xyloglucan oligosaccharides was generated, structurally characterized by mass spectrometry and NMR spectroscopy, and established as analytical standard compounds. Coupling of HPAEC with parallel electrochemical and MS detection was demonstrated to be an excellent tool to analyze xyloglucan-derived oligosaccharides. The applicability of the method was demonstrated by characterizing the xyloglucan architecture from a set of nine economically relevant food plants from the botanical orders Caryophyllales (rhubarb, buckwheat, amaranth, and quinoa), Cucurbitales (Hokkaido squash), Laurales (avocado), Myrtales (pomegranate), and Sapindales (mango and orange) for the first time. In future studies, this method can ideally be used to monitor structural alterations of xyloglucans as a result of genetic engineering, plant/tissue maturation, and processing of plant material.

Cryptocarya kaengkrachanensis, a new species of Lauraceae from Kaeng Krachan National Park, southwest Thailand.

A new species of Lauraceae, Cryptocarya kaengkrachanensis M.Z.Zhang, Yahara & Tagane, from Kaeng Krachan National Park, Phetchaburi Province, southwestern Thailand, is described and illustrated. This species is morphologically most similar to C. amygdalina in that its leaves are pinnately veined, leathery, and apparently glabrous (but microscopically hairy) abaxially, twigs are yellowish brown hairy, and fruits are 1.36 to 1.85 times longer than width. However, C. kaengkrachanensis is distinguished from C. amygdalina in having the leaves of ovate and elliptic (vs. oblong-lanceolate) with leaf aspect ratio (length:width) from 1.38 to 2.28 (vs. 2.46-3.43), and ovoid fruits (vs. ellipsoid) with stalk distinctly swollen (vs. not or only slightly swollen). In addition, phylogenetic trees constructed based on internal transcribed spacer sequences (ITS) and genome-wide SNPs using MIG-seq showed that C. kaengkrachanensis is not sister to C. amygdalina and is distinct from all the other Cryptocarya species hitherto recognized in Thailand. Analysis including other species demonstrates that C. floribunda should be a synonym of C. amygdalina, but we recognize C. scortechinii as a distinct species.

A mosaic Lauralean flower from the Early Cretaceous of Myanmar.

PREMISE OF THE STUDY: The floral history of early angiosperms is far from complete. The fossil discussed here has the potential to expand our knowledge of timing, reproductive biology, and paleobiogeography in early angiosperms. METHODS: Cutting-edge methodologies in CT scanning in conjunction with tomography software have opened new possibilities for discovering details in amber-preserved fossils that were inaccessible for meaningful study in the past. KEY RESULTS: The fossil is small and complex, cupulate, with numerous stamens and a suite of characters distributed in the modern families of Laurales. The most parsimonious placement of the fossil based on morphology is as a sister taxon of Atherospermataceae + Gomortega (Gomortegaceae). CONCLUSIONS: This fossil taxon, a Laurasian Lauralean from the mid-Cretaceous, is an important example of fossil Laurales with implications for biogeography and timing in the radiation and extinction in this group.

Increased sampling of both genes and taxa improves resolution of phylogenetic relationships within Magnoliidae, a large and early-diverging clade of angiosperms.

Magnoliidae have been supported as a clade in the majority of large-scale molecular phylogenetic studies of angiosperms. This group consists of about 10,000 species assigned to 20 families and four orders, Canellales, Piperales, Laurales, and Magnoliales. Some relationships among the families are still largely debated. Here, we reconstruct the phylogenetic relationships of Magnoliidae as a whole, sampling 199 species (representing ca. 75% of genera) and 12 molecular markers from the three genomes (plastid atpB, matK, trnL intron, trnL-trnF spacer, ndhF, rbcL; mitochondrial atp1, matR, mtSSU, mtLSU; nuclear 18s rDNA, 26S rDNA). Maximum likelihood, Bayesian and maximum parsimony analyses yielded congruent trees, with good resolution and high support values for higher-level relationships. This study further confirms, with greater levels of support, two major clades in Magnoliidae: Canellales+Piperales and Laurales+Magnoliales. Relationships among the 20 families are, in general, well resolved and supported. Several previously ambiguous relationships are now well supported. For instance, the Aristolochiaceae s.l. (incl. Asaroideae, Aristolochioideae, and Lactoris) are monophyletic with high support when Hydnoraceae are excluded. The latter family was not included in most previous studies because of the lack of suitable plastid sequences, a consequence of the parasitic habit of its species. Here, we confirm that it belongs in Aristolochiaceae. Our analyses also provide moderate support for a sister group relationship between Lauraceae and Monimiaceae. Conversely, the exact position of Magnoliaceae remains very difficult to determine. This study provides a robust phylogenetic background to address the evolutionary history of an important and highly diverse clade of early-diverging angiosperms.