Genomics of Steinchisma (Panicoideae: Paspaleae) Anthony J. Studer1, Patrick P. Edger2 & Michael R. McKain3
1University of Illinois; 2Michigan State University; 3University of Alabama. astuder@illinois.edu
Over forty years ago researchers recognized the diversity of photosynthetic types among monocot species and their utility in understanding photosynthetic pathway evolution. However, early work was impeded by a lack of genomic technologies and an accurate taxonomic framework. Since then, genomic technologies have greatly advanced and a well-resolved phylogeny of the Paspaleae subtribe Otachyriinae has been completed. The subtribe Otachyriinae includes C3 and C3-C4 species in the genus Steinchisma, as well as sister C3 and C4 genera. We used long-read sequencing technologies to sequence and assemble the genome of Steinchisma hians, a C3-C4 intermediate species. This high quality genome assembly provides an anchor for genomic studies in this clade.
We have also successfully recreated the interspecies cross between S. hians and the C3 species Steinchisma laxum that was previously reported in the literature. With the updated phylogeny we are also attempting several new crosses that will bring together different photosynthetic types in interspecific hybrids. The combined genomic resources and unique hybrid germplasm are powerful resources for understanding the genomic changes underlying photosynthetic evolution.
Key words: C3-C4 intermediate, Panicoideae, Paspaleae, photosynthesis, Steinchisma.
Grass inflorescence evolution Renata Reinheimer1
1Instituto de Agrobiotecnología del Litoral (UNL, CONICET). rreinheimer@ial.santafe-conicet.gov.ar
Morphology of the grass inflorescence is known to be extremely variable among species, fascinating in its development and incredibly intriguing in its underlying genetics. Inflorescence forms displayed by grasses lead to a general assumption that their evolution is random. When grass inflorescence morphology was analyzed comparatively on a species phylogenetic framework, we have discovered that despite appearing extremely diverse at first sight, they followed common evolutionary trends. Currently, in our laboratory we are dedicated to investigating the molecular bases that promoted such macroevolutionary changes in the inflorescences of grasses. In particular, we focused on studying molecular mechanisms that determine the final fate of the apical and axillary meristems of the inflorescences. This talk will discuss some advances made in the study of genes (most of them, transcription factors) that played a key role in the evolution of grass inflorescence forms.
Key words: genetics, grasses, inflorecence, macroevolution, morphology.
The evolution of transcription factor protein-protein interactions and flower development in the grasses
Amanda Schrager-Lavelle1, Maria Jazmin Abraham Juarez1, Madelaine Bartlett1
1University of Massachusetts Amherst. mbartlett@bio.umass.edu
The evolution of gene regulation is central in the evolution of plant and animal form. Interactions between transcription factor proteins are of profound importance in determining gene expression patterns. This is particularly true of the floral MADS-box transcription factors, which likely function as part of tetrameric protein complexes. Current models predict that the precise
composition of these MADS-box tetramers determines downstream gene expression patterns and, in turn, floral organ identity. Arising from this model of MADS-box function is the hypothesis that shifting MADS-box protein-protein interactions affect downstream gene regulation, and thus drive evolutionary change. To test this hypothesis, we have developed an experimental system in Zea mays (maize) where we can manipulate MADS-box protein-protein interactions in an evolutionary context, and assess consequent impacts on global gene expression patterns and floral development.
We have found widespread transcriptional changes downstream of altered protein-protein interactions. In contrast, floral morphology is subtly affected. Our results have implications for understanding flower development and evolution in the grasses, and for understanding the mechanisms driving the evolution of gene regulation more broadly.
Key words: evo-devo, genetics, flower development, maize, transciption factors.
Funded by: National Science Foundation of the United States of America (IOS-1652380)
The use of low-copy nuclear genes in the delimitation of genera and species in the Andropogoneae (Panicoideae)
Cassiano A. Dorneles Welker1, Michael R. McKain2, Tatiana Teixeira de Souza-Chies3 & Elizabeth A. Kellogg4
1Universidade Federal de Uberlândia, Programa de Pós-Graduação em Biologia Vegetal, Rua Ceará s/n, Uberlândia, Minas Gerais 38400-902, Brazil; 2The University of Alabama, Department of Biological Science, 411 Mary Harmon Bryant Hall, Tuscaloosa, Alabama 35487, U.S.A.;
3Universidade Federal do Rio Grande do Sul, Programa de Pós-Graduação em Botânica, Av. Bento Gonçalves 9500, Porto Alegre, Rio Grande do Sul 91501-970, Brazil; 4Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, Missouri 63132, U.S.A.
cassiano_welker@yahoo.com.br
Andropogoneae is an economically and ecologically important group of grasses, which includes some of the world’s most important crops such as sugarcane, maize, and sorghum, as well as many dominant species in both tropical and temperate grassland vegetation formations. Polyploidy and reticulate evolution are common in Andropogoneae, making taxonomic delimitation of its genera and species difficult. Due to the high variability of the sequences and their ability for identifying hybrids, low-copy nuclear genes have proven to be great markers for reconstructing the phylogeny of Andropogoneae and circumscribing its genera and species. Phylogenetic trees inferred from nuclear genes are useful to understand the evolutionary relationships of polyploid taxa and identify allopolyploidization events because they produce characteristic double-labeled tree topologies in which the polyploid species appear twice. In such trees, allopolyploids can be recognized even in the absence of chromosome counts. Recently published papers based on low-copy nuclear genes have successfully delimited genera in several Andropogoneae lineages, including Eriochrysis, Saccharum, and Sorghum. Taxonomic circumscriptions of species complexes have also been elucidated. A recent study also showed that at least one third of Andropogoneae species resulted from allopolyploidy, with a remarkably high number of independent allopolyploidization events.
Key words: allopolyploidy, molecular cloning, reticulate evolution, species complex, taxonomy.
Diversity and evolution of rachilla appendages in the core panicoids (Poaceae - Panicoideae) Christian Silva1, Gerrit Davidse2, Maria Vorontsova3 & Reyjane Patrícia Oliveira1
1Universidade Estadual de Feira de Santana, Bahia, Brazil; 2Missouri Botanical Garden, USA;
3Royal Botanic Gardens, Kew, United Kingdom. christian_da_silva@hotmail.com
Panicoideae is the second largest lineage within Poaceae with 3,200+ species. Among its 12 tribes, Paniceae, Paspaleae, and Andropogoneae form a clade known as the core panicoids. The rachilla internode below the upper anthecium may be elongated in some genera of this clade, comprising a stipe, whereas in others it may also be expanded into appendages of various shapes. This feature of uncertain role may have high taxonomic significance, as in Ichnanthus. Here we put together the results previously obtained in taxonomic, phylogenetic, and macro- and micromorphological studies on taxa with rachilla appendages, exploring the diversity and evolution of this feature within the core panicoids. The molecular phylogenies have contradicted the traditional classifications, resulting in the proposition of new genera and reestablishment or synonymization of others. The appendages may be of homogeneous or heterogeneous morphology (as in Hildaea and Panicum sect. Rudgeana, respectively) and have multiple independent origins within the core panicoids. Oils found in the appendages of some species suggest myrmecochory, but data on dispersal is lacking.
Ontogeny of the appendages is also unknown, and their phylogenetic distribution and influence on the diversification of certain groups need to be better explored, as well as possible coevolution with ants.
Key words: fruit dispersal, grasses, independent evolution, molecular phylogeny, myrmecochory.
Generic realignments in Paniceae and Paspaleae (Panicoideae) Fernando Zuloaga 1
1Instituto de Botánica Darwinion. fzuloaga@darwin.edu.ar
Included in the PACMAD clade of the family, tribes Paniceae and Paspaleae are, together with the Andropogoneae, the largest tribes of the subfamily Panicoideae, with more than 122 genera and nearly 2000 species. Paniceae and Paspaleae include a huge morphological, cytological and physiological diversity represented by different inflorescence types, several basic chromosome numbers, and at least four major photosynthetic pathways. The x = 10 Paspaleae is sister to the Andropogoneae–Arundinelleae s.s. clade (x = 10), while the combined x = 10 clade is sister to the x
= 9 clade that contains the remaining genera of Paniceae. Within tribe Paspaleae, we here review relationships, and new alignments, in subtribes Paspalineae, Otachyriinae, and Arthropogoninae. On the other hand, new results are discussed in incertae sedis genera of tribe Paniceae, and in subtribes Dichantheliinae, Melinidinae, Panicinae, and Cenchrinae. Finally, a new classification of Panicum s. str., highlighting its morphological characters, is presented; species to be excluded from the genus are discussed. Relationships with incertae sedis genera, and those classified in the Boivinellinae, Melinidineae, and Cenchrinae are also considered.
Key words: Paniceae, Panicum, Paspaleae, systematics, taxonomy.