The evolution of floral symmetry across the plant order Lamiales

Bilaterally symmetrical corollas have evolved independently numerous times from radially symmetrical ancestors and are thought to represent adaptation to specific pollinators. However, evolutionary losses of bilateral symmetry have occurred sporadically in different lineages. CYC2-like and RAD-like are genes needed for the normal development of bilateral symmetry in snapdragon corollas. However, exactly how changes in the floral symmetry patterning genes correlate with the origin and loss of floral bilateral remains poorly known. To address this question, a densely sampled phylogeny of CYC2-like genes across the order Lamiales was inferred and calibrated. The expression patterns of these genes in early diverging and higher core clades were also examined. The phylogeny indicated at least four independent duplications of CYC2-like genes in four major lineages of Lamiales around the Cretaceous-Paleogene (K-Pg) boundary, coinciding with the initial diversification of bumble bees and euglossine bees. Losses of CYC2-like paralogs were common, but did not correlate with a corresponding loss in floral symmetry. Relaxed positive selection occurred concurrently with retention of duplicates. CYC2-like paralogs showed differential expression, and asymmetrical expression of individual CYC2-like genes in adaxial and lateral petals correlated with the independent origins of floral zygomorphy in core Lamiales. The expression patterns of CYC2-like genes have evolved in a stepwise fashion. CYC2-like was expressed only very early in development in Oleaceae, while persistent expression of CYC2-like in petals originated in the common ancestor of Tetrachondraceae and core Lamiales. Asymmetrical expression in adaxial and lateral petals appeared later with the common ancestor of the core Lamiales. Similarly, expression of RAD-like in petals appeared in early diverging Lamiales or earlier, while asymmetrical expression in adaxial and lateral petals appeared later with Plantaginaceae and Gesneriaceae. Flowers of three radially symmetrical members of Lamiaceae were studied in detail, and the results indicated that each achieved radial symmetry in a different way. Development and expression of CYC2-like genes in Lycopus were similar to those of their bilaterally symmetrical relatives. However, expanded expression of CcCYC2A correlated with a radially symmetrical corolla in Callicarpa. Finally, loss of CYC2A and altered expression of CYC2Bs may account for the early bilateral symmetry but late radial symmetry in Mentha

Five Nuclear Loci Resolve the Polyploid History of Switchgrass (Panicum virgatum L.) and Relatives

Polyploidy poses challenges for phylogenetic reconstruction because of the need to identify and distinguish between homoeologous loci. This can be addressed by use of low copy nuclear markers. Panicum s.s. is a genus of about 100 species in the grass tribe Paniceae, subfamily Panicoideae, and is divided into five sections. Many of the species are known to be polyploids. The most well-known of the Panicum polyploids are switchgrass (Panicum virgatum) and common or Proso millet (P. miliaceum). Switchgrass is in section Virgata, along with P. tricholaenoides, P. amarum, and P. amarulum, whereas P. miliaceum is in sect. Panicum. We have generated sequence data from five low copy nuclear loci and two chloroplast loci and have clarified the origin of P. virgatum. We find that all members of sects. Virgata and Urvilleana are the result of diversification after a single allopolyploidy event. The closest diploid relatives of switchgrass are in sect. Rudgeana, native to Central and South America. Within sections Virgata and Urvilleana, P. tricholaenoides is sister to the remaining species. Panicum racemosum and P. urvilleanum form a clade, which may be sister to P. chloroleucum. Panicum amarum, P. amarulum, and the lowland and upland ecotypes of P. virgatum together form a clade, within which relationships are complex. Hexaploid and octoploid plants are likely allopolyploids, with P. amarum and P. amarulum sharing genomes with P. virgatum. Octoploid P. virgatum plants are formed via hybridization between disparate tetraploids. We show that polyploidy precedes diversification in a complex set of polyploids; our data thus suggest that polyploidy could provide the raw material for diversification. In addition, we show two rounds of allopolyploidization in the ancestry of switchgrass, and identify additional species that may be part of its broader gene pool. This may be relevant for development of the crop for biofuels

Comparative Transcriptomics Indicates a Role for SHORT VEGETATIVE PHASE (SVP) Genes in Mimulus guttatus Vernalization Response

The timing of reproduction in response to variable environmental conditions is critical to plant fitness, and is a major driver of taxon differentiation. In the yellow monkey flower, Mimulus guttatus, geographically distinct North American populations vary in their photoperiod and chilling (vernalization) requirements for flowering, suggesting strong local adaptation to their surroundings. Previous analyses revealed quantitative trait loci (QTL) underlying short-day mediated vernalization responsiveness using two annual M. guttatus populations that differed in their vernalization response. To narrow down candidate genes responsible for this variation, and to reveal potential downstream genes, we conducted comparative transcriptomics and quantitative PCR (qPCR) in shoot apices of parental vernalization responsive IM62, and unresponsive LMC24 inbred lines grown under different photoperiods and temperatures. Our study identified several metabolic, hormone signaling, photosynthetic, stress response, and flowering time genes that are differentially expressed between treatments, suggesting a role for their protein products in short-day-mediated vernalization responsiveness. Only a small subset of these genes intersected with candidate genes from the previous QTL study, and, of the main candidates tested with qPCR under nonpermissive conditions, only SHORT VEGETATIVE PHASE (SVP) gene expression met predictions for a population-specific short-day-repressor of flowering that is repressed by cold

Discussion on technical system and practice of green highway construction

This paper proposes the framework of the construction and management system of the Puyan Green Highway in Sanming, the technology of environmental protection and pollution prevention, the technology of resource conservation and recycling, the technology of green environmental protection and energy conservation and carbon reduction, the service improvement and smart construction technologies On this basis, the research and practice of green highway construction demonstration technology have been carried out, laying a practical foundation for the construction of green highways in Fujian Province

Summary trees for each of the nDNA regions and the combined nDNA tree, based on data sets with ∼83 accessions.

<p>We use letters to indicate well-supported clades, and infer that these correspond to genomic groups.</p

Divergent genomes within Panicum s.s. as inferred from nDNA clades.

*<p>Asterisks indicate that the genome was found in some but not all species in a particular taxonomic section. (In contrast, genomes A and B were found in all sampled members of sections <i>Urvilleana</i> and <i>Virgata</i>, while genome F was found in all sampled members of section <i>Panicum</i>).</p>**<p>Diploid species are underlined.</p

Summary of inferred ploidy levels and genomic compositions for taxa in the current study.

<p>Ploidy levels were inferred from sequence types, flow cytometry, and cytological studies. The symbol (+) indicates that other genomic components were suggested in some analyses, but not characterized further in the current study.</p

Flow cytometry results.

<p>Predicted ploidy levels as measured by flow cytometry. Estimates based on multiple samples of the same individual are indicated with parenthetical numbers; those based on different individuals representing the same accession are indicated with hyphenated numbers.</p