ARTICLE | doi:10.20944/preprints201811.0071.v1
Subject: Life Sciences, Other Keywords: basal angiosperms; chloroplast; comparative genomics; Nymphaeales; Nymphaeaceae; phylogenomics; water lily
Online: 2 November 2018 (16:20:31 CET)
The order Nymphaeales, consisting of three families with a record of eight genera, has gained significant interest from botanists probably due to its position as a basal-angiosperm. The phylogenetic relationships within the order have well been studied and resolved; however, a few controversial nodes still remain in the Nymphaeaceae including the position of the genus Nuphar. The position of the genus Nuphar and the monophyly of the Nymphaeaceae family remain uncertain. This study adds to the increasing number of completely sequenced plastid genomes of the Nymphaeales and applies large chloroplast gene data set in reconstructing the intergeneric relationships within the Nymphaeaceae. Five complete chloroplast genomes were newly generated, including a first one for the monotypic genus Euryale. Using a set of 66 protein coding genes from the chloroplast genomes of 17 taxa, the phylogenetic position of Nuphar was determined and a monophyletic Nymphaeaceae family was obtained with a convincing statistical support from both partitioned and unpartitioned data schemes. Although genomic comparative analyses revealed a high degree of synteny among the chloroplast genomes of the ancient angiosperms, key minor variations were evident particularly in the contraction/expansion of the Inverted Repeat regions and in RNA editing events. Genome structure, gene content and arrangement were highly conserved among the chloroplast genomes.
ARTICLE | doi:10.20944/preprints201801.0280.v1
Subject: Biology, Plant Sciences Keywords: cold stress; heat stress; stress recovery; mitochondria; proteomics; respiration; Brassica; angiosperms
Online: 30 January 2018 (10:31:07 CET)
Complex proteomic and physiological approaches to study cold and heat stress responses in plant mitochondria are still limited. Variations in the mitochondrial proteome of cauliflower (Brassica oleracea var. botrytis) curds after cold and heat and after stress recovery were assayed by 2D PAGE in relation to respiratory parameters. Quantitative analysis of the mitochondrial proteome revealed numerous stress-affected protein spots. In cold alternative oxidase isoforms were extensively upregulated; major downregulations in the level of photorespiratory enzymes, porine isoforms, oxidative phosphorylation (OXPHOS) and some low-abundant proteins were observed. On the contrary, distinct proteins, including carbohydrate metabolism enzymes, heat-shock proteins, translation, protein import, and OXPHOS components were involved in heat response and recovery. Few metabolic regulations were suggested. Cauliflower plants appeared less susceptible to heat; closed stomata in heat stress resulted in moderate photosynthetic, but only minor respiratory impairments, however photosystem II performance was unaffected. Decreased photorespiration corresponded with proteomic alterations in cold. Our results show that cold and heat stress not only operate in diverse mode (exemplified by cold-specific accumulation of some heat shock proteins), but exert some associations on molecular and physiological levels. This implies more complex model of action of investigated stresses on plant mitochondria.
ARTICLE | doi:10.20944/preprints202201.0113.v1
Subject: Biology, Plant Sciences Keywords: Group II; Intron; Splicing; PPR; Respiration; Complex I; Mitochondria; Embryogenesis; Arabidopsis; Angiosperms.
Online: 10 January 2022 (12:46:06 CET)
Mitochondria play key roles in cellular energy metabolism in eukaryotes. Mitochondria of most organisms contain their own genome and specific transcription and translation machineries. The expression of angiosperm mtDNA involves extensive RNA-processing steps, such as RNA trimming, editing, and the splicing of numerous group II-type introns. Pentatricopeptide repeat (PPR) proteins are key players of plant organelle gene expression and RNA metabolism. In the present analysis, we reveal the function of the MITOCHONDRIAL SPLICING FACTOR 2 gene (MISF2, AT3G22670) and show that it encodes a mitochondria-localized PPR protein that is crucial for early embryo-development in Arabidopsis. Molecular characterization of embryo-rescued misf2 plantlets indicates that the splicing of nad2 intron 1 and thus respiratory complex I biogenesis are strongly compromised. Moreover, the molecular function seems conserved between MISF2 protein in Arabidopsis and its orthologous gene (EMP10) in maize, suggesting that the ancestor of MISF2/EMP10 was recruited to function in nad2 processing before the monocot-dicot divergence, ~200 million years ago. These data provide new insights into the function of nuclear-encoded factors in mitochondrial gene expression and respiratory chain biogenesis during plant embryo development.
ARTICLE | doi:10.20944/preprints201905.0002.v1
Subject: Biology, Plant Sciences Keywords: codon position; complete chloroplast; early-diverging angiosperms; monophyly; Nymphaeaceae; Nymphaeales; plastid genome; phylogenomics; repeatability
Online: 3 May 2019 (14:03:46 CEST)
The monophyly of Nymphaeaceae (water lilies) represents a critical question in understanding the evolutionary history of early-diverging angiosperms. A recent plastid phylogenomic investigation claimed new evidence for the monophyly of Nymphaeaceae, but its results could not be verified from the available data. Moreover, preliminary gene-wise analyses of the same dataset provided partial support for the paraphyly of the family. The present investigation aims to re-assess the previous conclusion of the monophyly of Nymphaeaceae under the same dataset and to determine the congruence of the phylogenetic signal across different plastome genes and data partition strategies. To that end, phylogenetic tree inference is conducted on each of 78 protein-coding plastome genes, both individually and upon concatenation, and under four data partitioning schemes. Moreover, the possible effects of various sequence variability and homoplasy metrics on the inference of specific phylogenetic relationships are tested using multiple logistic regression. Differences in the variability of polymorphic sites across codon positions are assessed using parametric and non-parametric analysis of variance. The results of the phylogenetic reconstructions indicate considerable incongruence among the different gene trees as well as the data partitioning schemes. The results of the multiple logistic regression tests indicate that the fraction of polymorphic sites of codon position 3 has a significant effect on the recovery of the monophyly of Nymphaeaceae. Taken together, these results indicate that the monophyly of Nymphaeaceae currently remains indeterminate, and that specific phylogenetic conclusions are strongly dependent on the precise plastome gene, data partitioning scheme, and codon position evaluated. In closing, I discuss the importance of archiving all data of an investigation in publicly accessible data repositories, along with sufficient details to replicate the published results, and provide recommendations on future plastid phylogenomic investigations of Nymphaeales.