Studies of hybridization and chromosome number variation in aquatic angiosperms: evolutionary implications

An index of chromosome numbers for spermatophytes indigenous to the New Zealand Botanical Region is presented, along with full references to the original reports. Chromosome numbers are listed for 1212 species out of a total estimated indigenous spermatophyte flora of 1883 described species. This represents 64.4% of the total with chromosome counts (100% for gymno‐sperms, 74.3% for dicotyledons, and 39.8% for monocotyledons).

https://www.tandfonline.com/doi/pdf/10.1080/0028825X.2000.9512672

Index of chromosome numbers of indigenous New Zealand spermatophytes

The Lemna genus is a group of monocotyledonous plants with tiny, floating bodies. Lemna gibba G3 and L. paucicostata 6746 were once intensively analyzed for physiological timing systems of photoperiodic flowering and circadian rhythms since they showed obligatory and sensitive photoperiodic responses of a long-day and a short-day plant, respectively. We attempted to approach the divergence of biological timing systems at the molecular level using these plants. We first employed molecular techniques to study their circadian clock systems. We developed a convenient bioluminescent reporter system to monitor the circadian rhythms of Lemna plants. As in Arabidopsis, the Arabidopsis CCA1 promoter produced circadian expression in Lemna plants, though the phases and the sustainability of bioluminescence rhythms were somewhat diverged between them. Lemna homologs of the Arabidopsis clock-related genes LHY/CCA1, GI, ELF3 and PRRs were then isolated as candidates for clock-related genes in these plants. These genes showed rhythmic expression profiles that were basically similar to those of Arabidopsis under light-dark conditions. Results from co-transfection assays using the bioluminescence reporter and overexpression effectors suggested that the LHY and GI homologs of Lemna can function in the circadian clock system like the counterparts of Arabidopsis. All these results suggested that the frame of the circadian clock appeared to be conserved not only between the two Lemna plants but also between monocotyledons and dicotyledons. However, divergence of gene numbers and expression profiles for LHY/CCA1 homologs were found between Lemna, rice and Arabidopsis, suggesting that some modification of clock-related components occurred through their evolution.

/pdf/conserved-expression-profiles-of-circadian-clock-related-4n9bzlr2ae.pdf

Conserved Expression Profiles of Circadian Clock-related Genes in Two Lemna Species Showing Long-day and Short-day Photoperiodic Flowering Responses

Documented chromosome numbers are reported for 187 taxa (170 species, 9 subspecies, 8 varieties), 5 hybrids (four putative, one artificial), and 18 of uncertain rank from 50 families (84 genera; 2 lycophyte, 11 pterophyte and 71 anthophyte). Of these, 189 counts are new for the New Zealand flora (167 of these are from named taxa). Many of the counts reported are from more poorly investigated families (e.g., Cyperaceae, Lycopodiaceae, Pota‐mogetonaceae) and genera (e.g., Desmoschoenus, Freycinetia, Lycopodiella, Lycopodium, Potamo‐geton, Schoenus), indigenous to New Zealand, or from nationally uncommon and/or threatened taxa (e.g., Eleocharis neozelandica, Hebe societatis, Myriophyllum robustum, and Pittosporum dallii), and/or newly described plants (e.g., Gingidia gri‐sea, Olearia adenocarpa), while three counts are from naturalised species (Alternanthera sessilis, Nephrolepis cordifolia, and Senecio skirrhodon), and one from a cultivated plant of Metrosideros nervulosa. In the majority of genera...

https://www.tandfonline.com/doi/pdf/10.1080/0028825X.2004.9512936

Contributions to a chromosome atlas of the New Zealand flora ‐ 38. Counts for 50 families

Despite rapid doubling time, simple architecture and ease of metabolic labelling, a lack of genetic tools in the Lemnaceae (duckweed) has impeded the full implementation of this organism as a model for biological research. Here, we present technologies to facilitate high-throughput genetic studies in duckweed. We developed a fast and efficient method for producing Lemna minor stable transgenic fronds via Agrobacterium-mediated transformation and regeneration from tissue culture. Additionally, we engineered an artificial microRNA (amiRNA) gene silencing system. We identified a Lemna gibba endogenous miR166 precursor and used it as a backbone to produce amiRNAs. As a proof of concept we induced the silencing of CH42, a magnesium chelatase subunit, using our amiRNA platform. Expression of CH42 in transgenic L. minor fronds was significantly reduced, which resulted in reduction of chlorophyll pigmentation. The techniques presented here will enable tackling future challenges in the biology and biotechnology of Lemnaceae.

/pdf/efficient-transformation-and-artificial-mirna-gene-silencing-2ufhjhxk3j.pdf

Krystyna Urbanska-Worytkiewicz

Papers

Cytological variation within Lemna L.