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Aim: Many plants, especially at high latitudes, have both widespread and highly discontinuous geographical distributions. To increase understanding of how such patterns originate, we examine genetic patterns in the arctic-alpine plant Sibbaldia procumbens. We evaluate the contributions of réfugia and the role of long-distance dispersal in shaping the current range of this species. Location: Northern Hemisphere, especially North America. Methods: We sampled Sibbaldia from 176 localities, including 168 for S. procumbens. We analysed sequence variation in three plastid DNA non-coding regions (the atpl-atpH and trnL-trnY intergenic spacers and the trnL · intron), performed Bayesian phylogenetic analyses and statistical parsimony analyses on the combined sequences, and analysed the geographical patterns of haplotype distribution and genetic diversity using data from all populations. Results: Sibbaldia procumbens probably originated in the mountains of South and East Asia. We identified highly distinct clades in Europe and North America, which overlapped on oceanic islands of the North Atlantic indicating long-distance dispersal capability. The North American dade included two lineages, one in California and the other widely distributed across the continent and North Atlantic.Haplotype diversity in the latter lineage was markedly higher to the south, suggesting mid-late Pleistocene southward displacement of North American populations with subsequent migration northwards into previously glaciated regions. In Europe, disjunct geographical regions generally harboured distinct haplotypes. Main conclusions: Multiple Pleistocene réfugia for S. procumbens occurred in both North America and Europe. North American réfugia existed in California and in the southern Rocky Mountains, but in contrast with most widespread arctic—alpine species we found no evidence for a Beringian refugium. Cryptic réfugia may have existed within the Cordilleran Ice Sheet. Episodes of range expansion and contraction and long-distance dispersal have all contributed to the genetic structure and widespread but fragmented distribution of this species.

For nearly all species in the three genera of tribe Sinningieae (Gesneriaceae), Sinningia, Paliavana, and Vanhouttea (mostly in southeastern Brazil) plus 10 outgroups, we have sequenced six non-coding DNA regions (i.e., plastid intergenic spacers trnT-trnL, trnL-trnF, trnS-trnG, atpB-rbcL, and introns in the trnL and rpl16 genes) and four introns in nuclear plastid-expressed glutamine synthetase gene (ncpGS). Separate and combined analyses of these data sets using maximum parsimony supported the monophyly of Sinningieae, but the genera Paliavana and Vanhouttea were found embedded within Sinningia; therefore a new infrageneric classification is here proposed. Mapping of pollination syndromes on the DNA-based trees supported multiple origins of hummingbird and bee syndromes and derivation of moth and bat syndromes from hummingbird flowers. Perennial tubers were derived from perennial stems in non-tuberous plants.

Plastid microsatellites are simple mono/dinucleotide repeats that can cause in-vitro taq polymerase errors leading to 'stutter' peaks that reduce the clarity and reliability of electropherograms. As an efficient and automated barcoding protocol requires high-quality raw data, this paper investigates the suitability of the psbA-trnH and atpF-H regions of the plastid genome for automated barcoding purposes. Amplification of 92 individuals from species pairs and triplets was undertaken. Of these, 59% of atpF-H species samples and 36% of psbA-trnH species samples showed evidence of microsatellite-induced errors in electropherogram bae calling. The downsream necessity of human intervention renders these non-coding regions sub-optimal for barcoding purposes.

Systematic and evolutionary relationships within the diploid Western Mediterranean Phlomis crinita/lychnitis complex remain controversial apparently due to hybridization and introgression. This study examines patterns of sequence variation in the nuclear ribosomal DNA (ITS region) and three non-coding plastid DNA regions (trnH-psbA, trnT-trnL and atpB-rbcL) in this complex in an aim to clarify whether hybridization, introgression or lineage sorting resulting from recent diversification is mainly responsible for poorly understood relationships. Information recovered from nuclear and chloroplast markers was found to be strongly incongruent. Phylogenetic analysis of inferred nuclear ITS ribotypes is consistent with previous morphometric and taxonomic results in distinguishing two sister lineages, P. crinita s.l. and P. lychnitis. In addition, the high number of additive polymorphisms detected in ITS sequences suggests the sharing of ancestral variability and local patterns of gene flow within the complex. In contrast, the pattern of chloroplast haplotype variation is geographic rather than taxonomic, which might be caused by low mutation rates combined with frequent instances of interspecific hybridization. To integrate the apparently discordant plastid and nuclear evidence, we suggest that both lineage sorting and horizontal transfer have been involved. Even though pinpointing cases due to either phenomenon is difficult, the available data provide evidence of two sister lineages where hybridization events can be identified despite the inheritance of ancestral polymorphisms.

Background Unlike Transposable Elements (TEs) and gene/genome duplication, the role of the so-called nuclear plastid DNA sequences (NUPTs) in shaping the evolution of genome architecture and function remains poorly studied. We investigate here the functional and evolutionary fate of NUPTs in the orphan crop Moringa oleifera (moringa), featured by the highest fraction of plastid DNA found so far in any plant genome, focusing on (i) any potential biases in their distribution in relation to specific nuclear genomic features, (ii) their contribution to the emergence of new genes and gene regions, and (iii) their impact on the expression of target nuclear genes. Results In agreement with their potential mutagenic effect, NUPTs are underrepresented among structural genes, although their overall transcription levels and broadness were only lower when involved exonic regions; the occurrence of plastid DNA generally did not result in a broader expression, except among those affected in introns by older NUPTs. In contrast, we found a strong enrichment of NUPTs among specific superfamilies of retrotransposons and several classes of RNA genes, including those participating in the protein biosynthetic machinery (i.e., rRNA and tRNA genes) and a specific class of regulatory RNAs. A significant fraction of NUPT RNA genes was found to be functionally expressed, thus potentially contributing to the nuclear pool. Conclusions Our results complete our view of the molecular factors driving the evolution of nuclear genome architecture and function, and support plastid DNA in moringa as a major source of (i) genome complexity and (ii) the nuclear pool of RNA genes.

This article focuses on the molecular and hormonal mechanisms underlying the control of fleshy fruit ripening and quality. Recent research on tomato shows that ethylene, acting through transcription factors, is responsible for the initiation of tomato ripening. Several other hormones, including abscisic acid (ABA), jasmonic acid (JA) and brassinosteroids (BR), promote ripening by upregulating ethylene biosynthesis genes in different fruits. Changes to histone marks and DNA methylation are associated with the activation of ripening genes and are necessary for ripening initiation. Light, detected by different photoreceptors and operating through ELONGATED HYPOCOTYL 5(HY5), also modulates ripening. Re-evaluation of the roles of ‘master regulators’ indicates that MADS-RIN, NAC-NOR, Nor-like1 and other MADS and NAC genes, together with ethylene, promote the full expression of genes required for further ethylene synthesis and change in colour, flavour, texture and progression of ripening. Several different types of non-coding RNAs are involved in regulating expression of ripening genes, but further clarification of their diverse mechanisms of action is required. We discuss a model that integrates the main hormonal and genetic regulatory interactions governing the ripening of tomato fruit and consider variations in ripening regulatory circuits that operate in other fruits.

Peridinin-containing dinoflagellate plastomes are predominantly encoded in nuclear genomes, with less than 20 essential chloroplast proteins carried on “minicircles”. Each minicircle generally carries one gene and a short non-coding region (NCR) with a median length of approximately 400–1000 bp. We report here differential nuclease sensitivity and two-dimensional southern blot patterns, suggesting that dsDNA minicircles are in fact the minor forms, with substantial DNA:RNA hybrids (DRHs). Additionally, we observed large molecular weight intermediates, cell-lysate-dependent NCR secondary structures, multiple bidirectional predicted ssDNA structures, and different southern blot patterns when probed with different NCR fragments. In silico analysis suggested the existence of substantial secondary structures with inverted repeats (IR) and palindrome structures within the initial ~650 bp of the NCR sequences, in accordance with conversion event(s) outcomes with PCR. Based on these findings, we propose a new transcription-templating-translation model, which is associated with cross-hopping shift intermediates. Since dinoflagellate chloroplasts are cytosolic and lack nuclear envelope breakdown, the dynamic DRH minicircle transport could have contributed to the spatial-temporal dynamics required for photosystem repair. This represents a paradigm shift from the previous understanding of “minicircle DNAs” to a “working plastome”, which will have significant implications for its molecular functionality and evolution.

RNase III proteins recognize double-stranded RNA structures and catalyze endoribonucleolytic cleavages that often regulate gene expression. Here, we characterize the functions of RNC3 and RNC4, two Arabidopsis thaliana chloroplast Mini-RNase III-like enzymes sharing 75% amino acid sequence identity. Whereas rnc3 and rnc4 null mutants have no visible phenotype, rnc3/rnc4 (rnc3/4) double mutants are slightly smaller and chlorotic compared with the wild type. In Bacillus subtilis, the RNase Mini-III is integral to 23S rRNA maturation. In Arabidopsis, we observed imprecise maturation of 23S rRNA in the rnc3/4 double mutant, suggesting that exoribonucleases generated staggered ends in the absence of specific Mini-III-catalyzed cleavages. A similar phenotype was found at the 3′ end of the 16S rRNA, and the primary 4.5S rRNA transcript contained 3′ extensions, suggesting that Mini-III catalyzes several processing events of the polycistronic rRNA precursor. The rnc3/4 mutant showed overaccumulation of a noncoding RNA complementary to the 4.5S-5S rRNA intergenic region, and its presence correlated with that of the extended 4.5S rRNA precursor. Finally, we found rnc3/4-specific intron degradation intermediates that are probable substrates for Mini-III and show that B. subtilis Mini-III is also involved in intron regulation. Overall, this study extends our knowledge of the key role of Mini-III in intron and noncoding RNA regulation and provides important insight into plastid rRNA maturation.

Cycadales is an extant group of seed plants occurring in subtropical and tropical regions comprising putatively three families and 10 genera. At least one complete plastid genome sequence has been reported for all of the 10 genera except Microcycas , making it an ideal plant group to conduct comprehensive plastome comparisons at the genus level. This article reports for the first time the plastid genome of Microcycas calocoma . The plastid genome has a length of 165,688 bp with 134 annotated genes including 86 protein-coding genes, 47 non-coding RNA genes (39 tRNA and eight rRNA) and one pseudogene. Using global sequence variation analysis, the results showed that all cycad genomes share highly similar genomic profiles indicating significant slow evolution and little variation. However, identity matrices coinciding with the inverted repeat regions showed fewer similarities indicating that higher polymorphic events occur at those sites. Conserved non-coding regions also appear to be more divergent whereas variations in the exons were less discernible indicating that the latter comprises more conserved sequences. Phylogenetic analysis using 81 concatenated protein-coding genes of chloroplast (cp) genomes, obtained using maximum likelihood and Bayesian inference with high support values (>70% ML and = 1.0 BPP), confirms that Microcycas is closest to Zamia and forms a monophyletic clade with Ceratozamia and Stangeria . While Stangeria joined the Neotropical cycads Ceratozamia , Zamia and Microcyas , Bowenia grouped with the Southern Hemisphere cycads Encephalartos , Lepidozamia and Macrozamia . All Cycas species formed a distinct clade separated from the other genera. Dioon , on the other hand, was outlying from the rest of Zamiaceae encompassing two major clades—the Southern Hemisphere cycads and the Neotropical cycads. Analysis of the whole cp genomes in phylogeny also supports that the previously recognized family—Stangeriaceae—which contained Bowenia and Stangeria , is not monophyletic. Thus, the cp genome topology obtained in our study is congruent with other molecular phylogenies recognizing only a two-family classification (Cycadaceae and Zamiaceae) within extant Cycadales.

Malpighiales are one of the most diverse orders of angiosperms. Molecular phylogenetic studies based on combined sequences of coding genes allowed to identify major lineages but hitherto were unable to resolve relationships among most families. Spacers and introns of the chloroplast genome have recently been shown to provide strong signal for inferring relationships among major angiosperm lineages and within difficult clades. In this study, we employed sequence data of the petD group II intron and the petB-petD spacer for a set of 64 Malpighiales taxa, representing all major lineages. Celastrales and Oxalidales served as outgroups. Sequence alignment was straightforward due to frequent microstructural changes with easily recognizable motifs (e.g., simple sequence repeats), and well defined mutational hotspots. The secondary structure of the complete petD intron was calculated for Idesia polycarpa as an example. Domains I and IV are the most length variable parts of the intron. They contain terminal A/T-rich stem-loop elements that are suggested to elongate independently in different lineages with a slippage mechanism earlier reported from the P8 stem-loop of the trnL intron. Parsimony and Bayesian analyses of the petD dataset yielded trees largely congruent with results from earlier multigene studies but statistical support of nodes was generally higher. For the first time a deep node of the Malpighiales backbone, a clade comprising Achariaceae, Violaceae, Malesherbiaceae, Turneraceae, Passifloraceae, and a Lacistemataceae-Salicaceae lineage received significant statistical support (83% JK, 1.00 PP) from plastid DNA sequences.