Verification of Chromosome Numbers in Utricularia floridana, an Aquatic, Carnivorous Plant Native to the Southeastern United States
Abstract
Previously, we conducted a cytological study of Utricularia floridana, an aquatic, carnivorous flowering plant of the Lentibulariaceae family, establishing a preliminary chromosome number of n=16 based on mitotic root tip counts. We aim to verify these results with meiotic counts from an additional population of this species. Lentibulariaceae are known for their extreme interspecific cytological variability, particularly within Utricularia and Genlisea: genomes in Genlisea show 24-fold differences in size between species, with 1C-values ranging from 63 Mbp in G. aurea (the smallest recorded in flowering plants) to 1510 Mbp in G. hispidula, and within Utricularia chromosome numbers range from n=6-40, with lengths spanning from ultra-diminutive to "normal". The accelerated molecular evolution in this clade of carnivorous plants (evidenced by extreme genomic variability between species) is of particular interest to plant geneticists. However, minute chromosome size coupled with an absence of roots (commonly used for mitotic chromosome counts), and a tendency to inhabit inconvenient habitats renders determination of chromosome numbers in this group difficult, such that fewer than 20% of the ca. 233 species of Utricularia have been counted. In June 2018 we collected numerous flower buds in different stages of development from a population of U. floridana growing in Smith Lake, Ordway-Swisher Biological Station, Putnam County, Florida. Flower buds were fixed in farmer's solution (3:1 ethanol-glacial acetic acid) for 24 hours, and stored in 70% ethanol. Anthers were removed, hydrolyzed for five minutes in 1N HCl, and macerated in aceto-orcein solution to release dividing pollen mother cells. Anther tissue was removed and cells were squashed under a coverslip to spread stained metaphase chromosomes. Samples were examined via light microscopy, and discrete cells with well-defined chromosomes imaged and counted. We anticipate that meiotic chromosome counts will verify our previous work in establishing a novel chromosome number for this enigmatic species.
Verification of Chromosome Numbers in Utricularia floridana, an Aquatic, Carnivorous Plant Native to the Southeastern United States
Previously, we conducted a cytological study of Utricularia floridana, an aquatic, carnivorous flowering plant of the Lentibulariaceae family, establishing a preliminary chromosome number of n=16 based on mitotic root tip counts. We aim to verify these results with meiotic counts from an additional population of this species. Lentibulariaceae are known for their extreme interspecific cytological variability, particularly within Utricularia and Genlisea: genomes in Genlisea show 24-fold differences in size between species, with 1C-values ranging from 63 Mbp in G. aurea (the smallest recorded in flowering plants) to 1510 Mbp in G. hispidula, and within Utricularia chromosome numbers range from n=6-40, with lengths spanning from ultra-diminutive to "normal". The accelerated molecular evolution in this clade of carnivorous plants (evidenced by extreme genomic variability between species) is of particular interest to plant geneticists. However, minute chromosome size coupled with an absence of roots (commonly used for mitotic chromosome counts), and a tendency to inhabit inconvenient habitats renders determination of chromosome numbers in this group difficult, such that fewer than 20% of the ca. 233 species of Utricularia have been counted. In June 2018 we collected numerous flower buds in different stages of development from a population of U. floridana growing in Smith Lake, Ordway-Swisher Biological Station, Putnam County, Florida. Flower buds were fixed in farmer's solution (3:1 ethanol-glacial acetic acid) for 24 hours, and stored in 70% ethanol. Anthers were removed, hydrolyzed for five minutes in 1N HCl, and macerated in aceto-orcein solution to release dividing pollen mother cells. Anther tissue was removed and cells were squashed under a coverslip to spread stained metaphase chromosomes. Samples were examined via light microscopy, and discrete cells with well-defined chromosomes imaged and counted. We anticipate that meiotic chromosome counts will verify our previous work in establishing a novel chromosome number for this enigmatic species.