Redox-related gene expression and sugar accumulation patterns are altered in the edible inflorescence produced by the cultivated form of pacaya palm (Chamaedorea tepejilote).

BACKGROUND AND AIMS: The pacaya palm is a dioecious neotropical palm species that is exploited in Latin America for its male inflorescence, which is edible when immature. It is cultivated, in a non-intensive manner, in Guatemala, where a morphotype occurs that produces much larger, more highly branched inflorescences compared with wild palms. We sought to identify molecular factors underlying this phenotypic divergence, which is likely to be a product of domestication. METHODS: We performed RNA-seq-based studies on immature pacaya palm male inflorescences in order to identify genes that might be directly or indirectly affected in their expression in relation to domestication. We also measured the accumulation of a range of soluble sugar molecules to provide information on the biochemical status of the two different types of material. KEY RESULTS: A total of 408 genes were found to display significantly different expression levels between the wild and cultivated morphotypes. Three different functional categories were found to be enriched in the gene set that was upregulated in the cultivated morphotype: redox balance; secondary metabolism; and transport. Several sugars were found to accumulate at higher levels in inflorescences of the cultivated morphotype, in particular myo-inositol, fructose and glucose. CONCLUSIONS: The observed upregulation of redox-related genes in the cultivated morphotype is corroborated by the observation of higher myo-inositol accumulation, which has been shown to be associated with enhanced scavenging of reactive oxygen species in other plants and which may affect meristem activity.

One maternal lineage leads the expansion of Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae) in the New and Old Worlds.

The bronze bug, Thaumastocoris peregrinus, an Australian native insect, has become a nearly worldwide invasive pest in the last 16 years and has been causing significant damage to eucalypts (Myrtaceae), including Eucalyptus spp. and Corymbia spp. Its rapid expansion leads to new questions about pathways and routes that T. peregrinus used to invade other continents and countries. We used mtDNA to characterize specimens of T. peregrinus collected from 10 countries where this species has become established, including six recently invaded countries: Chile, Israel, Mexico, Paraguay, Portugal, and the United States of America. We then combined our mtDNA data with previous data available from South Africa, Australia, and Europe to construct a world mtDNA network of haplotypes. Haplotype A was the most common present in all specimens of sites sampled in the New World, Europe, and Israel, however from Australia second more frequently. Haplotype D was the most common one from native populations in Australia. Haplotype A differs from the two major haplotypes found in South Africa (D and G), confirming that at least two independent invasions occurred, one from Australia to South Africa, and the other one from Australia to South America (A). In conclusion, Haplotype A has an invasion success over many countries in the World. Additionally, analyzing data from our work and previous reports, it is possible to suggest some invasive routes of T. peregrinus to predict such events and support preventive control measures.

Molecular phylogeny of the palm genus Chamaedorea, based on the low-copy nuclear genes PRK and RPB2.

Sequence data from the low-copy nuclear genes encoding phosphoribulokinase (PRK) and the second largest subunit of RNA polymerase II (RPB2) are used to generate the first phylogenetic analysis of Chamaedorea (Arecaceae: Arecoideae: Chamaedoreeae), the largest neotropical genus of palms. The prevailing current taxonomy of Chamaedorea recognizes approximately 100 species in eight subgenera, all delimited using floral characters, which provide a useful starting point to explore species-level systematics. Sequence data from 63 species, including representatives of all eight subgenera, were analyzed using maximum parsimony and Bayesian inference optimality criteria. Genus Chamaedorea is resolved as monophyletic with strong support in all separate and combined analyses. The less species-rich subgenera are convincingly monophyletic and can be diagnosed using morphological synapomorphies. In contrast, the two largest subgenera, Chamaedorea and Chamaedoropsis, which are supposedly distinguishable from each other by the degree of connation in the staminate petals, are both resolved as highly polyphyletic. Several well supported monophyletic groups resolved by these gene regions have never before been proposed within Chamaedorea and are challenging to delimit using morphological criteria. Although PRK proved more informative than RPB2, both regions have strong utility for interpreting species-level relationships among the palms, which are notoriously recalcitrant subjects for molecular phylogenetic studies. In addition, a paralog of the target copy of PRK identified during the analysis represents a potentially valuable source of phylogenetic information for future studies.