Symposium proposal |
Organizer: | Liangsheng Zhang (Zhejiang University) |
Co-organizer: | Fei Chen (Nanjing Agricultural University) |
Angiosperms (or flowering plants), the largest plant lineage, originated about 200 million years ago, and underwent dramatically rapid speciation within 100 million years. The molecular basis and mechanisms to the origin and diversity of angiosperms are critical questions in the plant, evolution and molecular ecology.The genomes are rich archives for understanding the fundamental genetic and evolutionary processes that generated biodiversity of flowering plants. Many genes are retained after polyploidization may be one of the most important factors leading to the origin of angiosperms. Compared with Amborella, the genomic characteristics and floral scent of water lilies are more like core angiosperms. Therefore, the floral and color characteristics of angiosperms originate at least from the common ancestors of water lilies and core angiosperms .This supports a scenario that early angiosperms had initiated the molecular mechanism underlying these functions, but further expansion and divergence of gene functions were facilitated by lineage specific Whole genome duplication events. Although there have been some clues about the origin and diversity of angiosperms, there are still many unknowns. As more and more genomes are sequenced, it will enable us to better understand the origin and diversity of angiosperms. |
S21-1
Phylogenomic analyses of gene duplications and evolution of developmental and physiological traits with implication for angiosperm diversity
Hong Ma1
1Department of Biology, the Huck Institutes of the Life Sciences, the Pennsylvania State University, University Park, PA, 16802 USA
Angiosperms are characterized by the production of fruits, which serve to protect developing seeds and subsequently facilitate seed dispersal, contributing to angiosperm diversity. Fruits display many morphological types and are classified into dry and fleshy fruits. In addition, other morphological and physiological traits are important for adaptation; such traits affecting angiosperm diversity include tendrils for climbing and root nodules for nitrogen fixation. The analyses of the evolutionary histories of fruit types and other traits is essential to the understanding of factors affecting angiosperm evolution and diversity, but are hampered by the uncertainties in the evolutionary relationships among members of a family or other taxonomic groups. We have performed phylogenomic and phylotranscriptomic analyses of nuclear genes to investigate the evolutionary relationships of several major angiosperm families, including Rosaceae, Cucurbitaceae, and Fabaceae, and probed the evolutionary histories of fruit types and other traits. In addition, phylotranscriptomic analyses detected clusters of gene duplications as strong evidence for supporting whole genome duplications (WGDs); these results support the idea that WGDs have contributed to the expansion of key genes important for fruit development, tendril formation and nitrogen-fixing nodulation. These results and their potential contribution to angiosperm diversity will be discussed.
S21-2
The making of elaborate petals in Nigella (Ranunculaceae)
Hongzhi Kong1
1State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
As a special type of floral organs, petals show tremendous diversity in shape, structure, color/coloration and function, and have increasingly been used as a model for the study of plant organ evolution. Petals of Nigella (Ranunculaceae) are of particular interest because they form highly elaborate, bilabiate structures with extensive modifications. To understand how Nigella petals become elaborate and diverse, we first investigated the morphology, micro-morphology and development of Nigella petals. We found that the degree of petal complexity increases gradually during the evolution of the genus, likely through modification of pre-existing characters (e.g., the elongation of stalk and the alteration of the upper and lower lips in shape) as well as de novo origination of new features (e.g., pseudonectaries, short trichomes, and eyebrow-like stripes). By conducting extensive developmental and evolutionary transcriptomic analyses and detailed expression and functional investigations, we identified the genes that play key roles in the elaboration and diversification of Nigella petals. We found that: 1) changes in the expression patterns of several transcription factors contribute to the formation of the upper lip (e.g., adaxial/abaxial polarity genes), the generation of pseudonectaries (e.g., YAB5), the bifurcation of the lower lip (e.g., LMI1), the development of long hairs and short trichomes (e.g., GL2, GL3, TT8 and LMI1), and the production of eyebrow-like stripes (e.g., MYB113); 2) evolutionary changes of some genes (e.g., ARF3-1, ARF4, KAN1, TT8, GL3, MYB113 and GASA14) in expression time and level may have led to the modifications of petal developmental trajectories and the origination of new characters (e.g., petal stalk, short trichomes, eyebrow-like stripes and pseudonectaries).These results confirmed that Nigella is an excellent model for the study of petal elaboration and pave the way for better understanding the basis and underlying mechanisms of plant organ diversification.
S21-3
Hybrid speciation via inheritance of alternate alleles of parental isolating genes
Jianquan Liu1
1Sichuan University
It is increasingly realized that homoploid hybrid speciation (HHS), which involves no change in chromosome number, is an important mechanism of speciation. HHS will likely increase in frequency as ecological and geographical barriers between species are continuing to be disrupted by human activities. HHS requires the establishment of reproductive isolation between a hybrid and its parents, but the underlying
genes and genetic mechanisms remain largely unknown. In this study, we reveal by integrated approaches that reproductive isolation originates in one homoploid hybrid plant species through the inheritance of alternate alleles at genes that determine parental premating isolation. The parent species of this hybrid species are reproductively isolated by differences in flowering time and survivorship on soils containing high concentrations of iron. We found that the hybrid species inherits alleles of parental isolating major genes related to flowering time from one parent and alleles of major genes related to iron tolerance from the other parent. In this way, it became reproductively isolated from one parent by the difference in flowering time and from the other by habitat adaptation (iron tolerance). These findings and further modeling results suggest that HHS may occur relatively easily via the inheritance of alternate parental premating isolating genes and barriers.
S21-4
The multi-omics analysis of Piper provide insight for angiosperms evolution
Lisong Hu1
1Spice and Beverage Research Institute, Chinese Academy of Tropical Agricultural Sciences
The origin and rapid evolution of early angiosperms is one of the core scientific issues in botany, which is known as “Abominable Mystery” of Darwin. The differentiation of floral organ, formation of kairomones/synomones in pollen and coevolution of insect pollinators, as well as functional diversification and neofunctionalization in genome evolution were regarded as the main causes of rapid development of early angiosperms. However, the evolution of piper genus with degeneration of floral organ, and rich in allomones, does not seem to follow this classical theory. Research on the characteristic of their evolution is little. Here, we found that the ancestor of genus piper was already existed in Gondwanaland period, which suggested an ancient origin of piper, and placed magnoliids as sister to the monocots-eudicots clade. The evolution of new piper species, diversity of allomones, the resistance to abiotic/biotic-stress are positively related. They retained a number of primitive features, such as degeneration of floral organ, diversity of allomones (piper alkaloids), the resistance to abiotic/biotic-stress, rather than the biosynthesis of kairomones/synomones, or the development of floral organ. Investigation into the mechanism of adaptive evolution of piper species based on genome evolution, phenotype differentiation and characteristic of secondary metabolite synthesis could complement new insight for evolution of angiosperms, which then to provide the theoretical reference for protection and utilization of Piper species under the changing climatic condition.
S21-5
The water lily genome reveals key innovations in angiosperm evolution
Fei Chen1
1College of horticulture, Nanjing Agricultural University
The water lily order Nymphaeales, together with Amborellales and Austrobaileyales form the so-called ANA-grade of angiosperms, which are extant representatives of lineages that diverged the earliest from the lineage leading to the extant mesangiosperms. Here we report the genome sequence of the water lilies. Our comprehensive phylogenomic analyses support Amborellales and Nymphaeales as successive sister lineages to all other extant angiosperms. The Nymphaea genome and other water lily transcriptomes reveal a Nymphaealean whole-genome duplication event, which is shared by Nymphaeaceae and possibly Cabombaceae. Among the genes retained from this whole-genome duplication are homologues of genes that regulate flowering transition and flower development. The broad expression of homologues of floral ABCE genes in water lilies might support a similarly broadly active ancestral ABCE model of floral organ determination in early angiosperms. Water lilies have evolved attractive floral scents and colours, which are features shared with mesangiosperms, and we identified their putative biosynthetic genes in water lilies. The chemical compounds and biosynthetic genes behind floral scents suggest that they have evolved in parallel to those in mesangiosperms. Because of its unique phylogenetic position, the water lily genomes shed light on the early evolution of angiosperms.