Eudicot Family Research Articles

Organization of the root apical meristem in angiosperms

Although flowers, leaves, and stems of the angiosperms have understandably received more attention than roots, the growing root tips, or root apical meristems (RAMs), are organs that could provide insight into angiosperm evolution. We studied RAM organization across a broad spectrum of angiosperms (45 orders and 132 families of basal angiosperms, monocots, and eudicots) to characterize angiosperm RAMs and cortex development related to RAMs. Types of RAM organization in root tips of flowering plants include open RAMs without boundaries between some tissues in the growing tip and closed RAMs with distinct boundaries between apical regions. Epidermis origin is associated with the cortex in some basal angiosperms and monocots and with the lateral rootcap in eudicots and other basal angiosperms. In most angiosperm RAMs, initials for the central region of the rootcap, or columella, are distinct from the lateral rootcap and its initials. Slightly more angiosperm families have exclusively closed RAMs than exclusively open RAMs, but many families have representatives with both open and closed RAMs. Root tips with open RAMs are generally found in angiosperm families considered sister to other families; certain open RAMs may be ancestral in angiosperms.

Phylogenetic systematics and character evolution in the angiosperm family Haloragaceae

The poorly known Haloragaceae R. Br. (Saxifragales) are highly diverse in habit (small trees to submerged aquatics) and labile in floral merosity (2-4), both uncommon among the core eudicots. This family has a cosmopolitan distribution, but taxonomic diversity is concentrated in Australia. An explicit phylogenetic approach has not previously been utilized to examine relationships or character evolution in this family. We used molecular evidence from nrDNA ITS and cpDNA trnK and matK regions under both Bayesian and parsimony analyses to address phylogenetic relationships. Combined molecular analyses defined a monophyletic Haloragaceae with the woody genera (Haloragodendron, Glischrocaryon) sister to the rest. Relationships among many genera were well resolved, with genera as currently delimited generally well supported, although there were notable exceptions; a new genus (Trihaloragis) is recognized, and the aquatic genus Meionectes is again distinct from Haloragis. Three new species combinations are also recognized. There are multiple (two or three) origins of the submerged aquatic habit in the family and potentially an intermediate reversal to the terrestrial habit, neither previously demonstrated in a core eudicot family using an explicit phylogenetic hypothesis. Ancestral character analyses suggest two origins of trimerous flowers and multiple reductions to dimerous flowers throughout Haloragaceae.

Preliminary identification and coat protein gene phylogenetic relationships of begomoviruses associated with native flora and cultivated plants from the Yucatan Peninsula of Mexico

A number of native and cultivated eudicots in the Yucatan Peninsula of Mexico (YPM) exhibit symptoms associated with virus infection. Symptomatic leaves were collected and assessed for begomoviral detection using polymerase chain reaction (PCR), and universal primers that amplify a fragment of the coat protein gene (core Cp). Begomovirus were detected in nine native and seven cultivated species, representing seven eudicot families. DNA extracts from the 16 hosts were used for PCR amplification and sequencing of a fragment containing the coat protein (Cp) gene. The complete Cp sequence was used to establish provisional species identification. Results indicated that 13 distinct begomovirus species were represented. Among these, five potentially new begomovirus species were identified, for which we propose the names Anoda golden mosaic virus (AnGMV), Boerhavia yellow spot virus (BoYSV), Papaya golden mosaic virus (PaGMV), Desmodium leaf distortion virus (DeLDV), and Hibiscus variegation virus (HiVV). Five previously described begomoviral species were provisionally identified for the first time in the YPM; these include Euphorbia mosaic virus (EuMV), Melon chlorotic leaf curl virus (MCLCuV), Okra yellow mosaic Mexico virus (OkYMMV), Sida golden mosaic virus (SiGMV), and Tobacco apical stunt virus (TbASV). Additionally, viruses previously reported from this region, Bean golden yellow mosaic virus (BGYMV), Pepper golden mosaic virus (PepGMV), and Tomato mottle virus (ToMoV) were provisionally identified in cultivated hosts. Phylogenetic analysis provisionally placed all isolates from the YPM in a Western Hemisphere begomovirus clade.

Phylogenetic relationship of native and introduced Bemisia tabaci (Homoptera: Aleyrodidae) from China and India based on mtCOI DNA sequencing and host plant comparisons

Abstract Phylogenetic relationships for Benisia tabaci were reconstructed by analysis of a ˜780 bp fragment of the mitochiondrial cytochrome oxidase I (mtCOI) gene with an emphasis on geographic range and distribution among eight eudicot plant families that are common hosts of B. tabaci worldwide to elucidate key phylogeographic linkages between populations extant in China (n=31) and India (n=34). Bootstrap values for the Maximum Parsimony tree were highly robust for all major nodes involving the major Asian clade, sub-groups, and sister groups within, at 92%—100%. Between-clade distances for the Southcast Asia and three otor major clades, e.g. from sub-Sahara Africa, North Africa-Mediterrancan, and the Americas, were approximately > 16% divergent. Two major Asian sub-groups (I, II) were resolved, which represented populations indigenous to the region, comprising two (I a, I b) and five (II a—e) sister groups, respectively, which diverged by 11%. Two distinct populations from sunflower in Hyderabad groupe...

Pollen Diversity and Evolution in Proteoideae (Proteales: Proteaceae)

Proteoideae (27 genera, 655 species) are one of the largest clades in the early-diverging eudicot family Proteaceae and are distributed in Australia, New Caledonia, and Africa. New palynological observations using scanning and transmission electron microscopy are reported for 15 genera and 49 species, which complement previous work on the subfamily. These are integrated with an extensive review of all literature data available to provide a summary of pollen morphology and variation in each genus of Proteoideae, using a new rigorous method of character scoring. The results are discussed in the context of recent phylogenetic analyses of Proteaceae. The monophyletic Leucadendreae, comprising two Australian genera and a large clade of 10 southern African genera, appear to be relatively homogenous in pollen morphology, especially in ultrastructure of the apertural region. In addition, two other African genera, Faurea and Protea, share very similar pollen characters, some of which appear to be apomorphic, consistent with strong phylogenetic evidence for their sister group relationship. Beauprea, Eidothea, Faurea, Protea, and Stirlingia share a distinct pattern of foot layer disintegration at the apertural region and complete lack of endexine. The occurrence of the same apertural type in the early-diverging Persoonioideae suggests that it is plesiomorphic in Proteoideae and Proteaceae as a whole. This study highlights the phylogenetic potential of ultrastructural characters in Proteaceae and high levels of homoplasy and polymorphism in other characters including pollen shape and tectum sculptural patterns.

Diversity of Kranz anatomy and biochemistry in C4 eudicots

C(4) photosynthesis and Kranz anatomy occur in 16 eudicot families, a striking example of convergent evolution. Biochemical subtyping for 13 previously undiagnosed C(4) eudicot species indicated that 10 were NADP-malic enzyme (ME) and three were NAD-ME. A total of 33 C(4) species, encompassing four Kranz anatomical types (atriplicoid, kochioid, salsoloid, and suaedioid), and 21 closely related C(3) species were included in a quantitative anatomical study in which we found that, unlike similar studies in grasses and sedges, anatomical type had no predictive value for the biochemical subtype. In a multivariate canonical discriminant analysis, C(4) species were distinguished from C(3) species by the mesophyll to bundle sheath ratio and exposure of the bundle sheath surface to intercellular space. Discrimination between NADP-ME and NAD-ME was not significant, although in a Mantel test grouping by biochemical subtype was significant, while grouping by family was not. This comprehensive survey of C(4) anatomy and biochemistry unequivocally demonstrated that atriplicoid anatomy and NADP-ME biochemistry predominate in many evolutionary lineages. In addition to a main decarboxylating enzyme, high activity of a second decarboxylating enzyme was often observed. Notably, PEP-carboxykinase activity was significant in a number of species, demonstrating that this enzyme could also serve as a secondary pathway for C(4) metabolism in eudicots.

Gene Relocations within Chloroplast Genomes of Jasminum and Menodora (Oleaceae) Are Due to Multiple, Overlapping Inversions

The chloroplast (cp) DNA sequence of Jasminum nudiflorum (Oleaceae-Jasmineae) is completed and compared with the large single-copy region sequences from 6 related species. The cp genomes of the tribe Jasmineae (Jasminum and Menodora) show several distinctive rearrangements, including inversions, gene duplications, insertions, inverted repeat expansions, and gene and intron losses. The ycf4-psaI region in Jasminum section Primulina was relocated as a result of 2 overlapping inversions of 21,169 and 18,414 bp. The 1st, larger inversion is shared by all members of the Jasmineae indicating that it occurred in the common ancestor of the tribe. Similar rearrangements were also identified in the cp genome of Menodora. In this case, 2 fragments including ycf4 and rps4-trnS-ycf3 genes were moved by 2 additional inversions of 14 and 59 kb that are unique to Menodora. Other rearrangements in the Oleaceae are confined to certain regions of the Jasminum and Menodora cp genomes, including the presence of highly repeated sequences and duplications of coding and noncoding sequences that are inserted into clpP and between rbcL and psaI. These insertions are correlated with the loss of 2 introns in clpP and a serial loss of segments of accD. The loss of the accD gene and clpP introns in both the monocot family Poaceae and the eudicot family Oleaceae are clearly independent evolutionary events. However, their genome organization is surprisingly similar despite the distant relationship of these 2 angiosperm families.

Floral organogenesis in Tetracentron sinense (Trochodendraceae) and its systematic significance

In Tetracentron sinense of the basal eudicot family Trochodendraceae, the flower primordium, together with the much retarded floral subtending bract primordium appear to form a common primordium. The four tepals and the four stamens are initiated in four distinct alternating pairs, the first tepal pair is in transverse position. The four carpels arise in a whorl and alternate with the stamens. This developmental pattern supports the interpretation of the flower as dimerous in the perianth and androecium, but tetramerous in the gynoecium. There is a relatively long temporal gap between the initiation of the stamens and the carpels. The carpel primordia are then squeezed into the narrow gaps between the four stamens. In contrast to Trochodendron, the residual floral apex after carpel formation is inconspicuous. In their distinct developmental dimery including four tepals and four stamens, flowers of Tetracentron are reminiscent of other, related basal eudicots, such as Buxaceae and Proteaceae.

Oil bodies in leaf mesophyll cells of angiosperms: overview and a selected survey

Neutral (storage) oil bodies occur in leaf mesophyll cells of many angiosperms, but their literature has been largely forgotten. We review this literature and provide a survey of 302 species and hybrids from mostly north-central US species representing 113 families. Freehand cross sections of fresh leaves stained with Sudan IV verified the presence of oil. In 71 species from 24 families we observed 1-15 oil bodies per mesophyll cell. The eudicot families Asteraceae, Caprifoliaceae, Lamiaceae, and Rosaceae had the highest number of species with oil bodies, whereas few or no species in the Apiaceae, Betulaceae, Fabaceae, and Scrophulariaceae had them. Only three of 19 monocot species sampled had oil bodies. Repeat sampling of a Malus (crabapple) cultivar and a Euonymus species showed conspicuous oil bodies in mid-summer and also in mid-autumn in both attached and recently shed leaves. Oil bodies in leaf mesophyll cells are conspicuous (visible in hand cross sections using moderate magnification in unstained water mounts) in numerous species, and they occur throughout the growing season in at least some species. Neutral oil bodies in leaf mesophyll cells are not mentioned in contemporary textbooks and advanced works, but they deserve recognition as significant cellular components of many taxa, in which they may be significant sources of commercial oils.

Combining Expression and Comparative Evolutionary Analysis. TheCOBRAGene Family

Plant cell shape is achieved through a combination of oriented cell division and cell expansion and is defined by the cell wall. One of the genes identified to influence cell expansion in the Arabidopsis (Arabidopsis thaliana) root is the COBRA (COB) gene that belongs to a multigene family. Three members of the AtCOB gene family have been shown to play a role in specific types of cell expansion or cell wall biosynthesis. Functional orthologs of one of these genes have been identified in maize (Zea mays) and rice (Oryza sativa; Schindelman et al., 2001; Li et al., 2003; Brown et al., 2005; Persson et al., 2005; Ching et al., 2006; Jones et al., 2006). We present the maize counterpart of the COB gene family and the COB gene superfamily phylogeny. Most of the genes belong to a family with two main clades as previously identified by analysis of the Arabidopsis family alone. Within these clades, however, clear differences between monocot and eudicot family members exist, and these are analyzed in the context of Type I and Type II cell walls in eudicots and monocots. In addition to changes at the sequence level, gene regulation of this family in a eudicot, Arabidopsis, and a monocot, maize, is also characterized. Gene expression is analyzed in a multivariate approach, using data from a number of sources, including massively parallel signature sequencing libraries, transcriptional reporter fusions, and microarray data. This analysis has revealed that the expression of Arabidopsis and maize COB gene family members is highly developmentally and spatially regulated at the tissue and cell type-specific level, that gene superfamily members show overlapping and unique expression patterns, and that only a subset of gene superfamily members act in response to environmental stimuli. Regulation of expression of the Arabidopsis COB gene family members has highly diversified in comparison to that of the maize COB gene superfamily members. We also identify BRITTLE STALK 2-LIKE 3 as a putative ortholog of AtCOB.

First nuclear DNA C-values for 18 eudicot families.

A key target set at the second Plant Genome Size Workshop, held at the Royal Botanic Gardens, Kew in 2003, was to produce first DNA C-value data for an additional 1 % of angiosperm species, and, within this, to achieve 75 % familial coverage overall (up from approx. 50 %) by 2009. The present study targeted eudicot families for which representation in 2003 (42.5 %) was much lower than monocot (72.8 %) and basal angiosperm (69.0 %) families. Flow cytometry or Feulgen microdensitometry were used to estimate nuclear DNA C-values, and chromosome counts were obtained where possible. First nuclear DNA C-values are reported for 20 angiosperm families, including 18 eudicots. This substantially increases familial representation to 55.2 % for angiosperms and 48.5 % for eudicots. The importance of targeting specific plant families to improve familial nuclear DNA C-value representation is reconfirmed. International collaboration will be increasingly essential to locate and obtain material of unsampled plant families, if the target set by the second Plant Genome Size Workshop is to be met.

Expression patterns of STM-like KNOX and Histone H4 genes in shoot development of the dissected-leaved basal eudicot plants Chelidonium majus and Eschscholzia californica (Papaveraceae)

Knotted-like homeobox (KNOX) genes encode important regulators of shoot development in flowering plants. In Arabidopsis, class I KNOX genes are part of a regulatory system that contributes to indeterminacy of shoot development, delimitation of leaf primordia and internode development. In other species, class I KNOX genes have also been recruited in the control of marginal blastozone fractionation during dissected leaf development. Here we report the isolation of class I KNOX genes from two species of the basal eudicot family Papaveraceae, Chelidonium majus and Eschscholzia californica. Sequence comparisons and expression patterns indicate that these genes are orthologs of SHOOTMERISTEMLESS (STM), a class I KNOX gene from Arabidopsis. Both genes are expressed in the center of vegetative and floral shoot apical meristems (SAM), but downregulated at leaf or floral organ initiating sites. While Eschscholzia californica STM (EcSTM) is again upregulated during acropetal pinna formation, in situ hybridization could not detect Chelidonium majus STM (CmSTM) transcripts at any stage of basipetal leaf development, indicating divergent evolution of STM gene function in leaves within Papaveraceae. Immunolocalization of KNOX proteins indicate that other gene family members may control leaf dissection in both species. The contrasting direction of pinna initiation in the two species was also investigated using Histone H4 expression. Leaves at early stages of development did not reveal notable differences in cell division activity of the elongating leaf axis, suggesting that differential meristematic growth may not play a role in determining the observed dissection patterns.

Shoot and compound leaf comparisons in eudicots: dynamic morphology as an alternative approach

Recent developmental studies suggest that the compound leaf is a more or less incompletely developed shoot. Instead of treating compound leaves and shoots as non-homologous, this interpretation draws a continuum between them. The present work considers the plant as a hierarchical series of units on which similar developmental processes are at work, and where each level (shoot, compound leaf, leaflet) is ‘repeated’ by the next higher level. Measurements related to the expression of developmental processes operating on leaves at the shoot level and on leaflets at the compound leaf level were used to determine if similar processes are at work at these different levels during early stages of organogenesis. Plants with compound leaves showing acropetal leaflet inception, representing a total of 16 species from ten eudicot families, were studied. Based on several types of quantitative analyses, there appears to be a continuum between so-called shoots, compound leaves and leaflets in the species studied. This perspective, qualified as dynamic morphology, both parallels and complements the classical interpretation. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 143, 219−230.

Phylogenetic Position of Dipentodon Sinicus: Evidence from DNA Sequences of Chloroplast rbcL, Nuclear Ribosomal 18S, and Mitochondria matR Genes

Phylogenctic position of the monotypic genus Dipentodon has long been controversial. We investigated its,:position with 125 accessions representing 50 genera and 40 families of eudicots in the APG system. Four data sets-including the chloroplast gene rbcL, the nuclear 18S ribosomal DNA, and the mitochondrial gene matR, as well as,,,the combined matrix-were used in the study with the maximum parsimony (MP) and Bayesian inference (131) analyses. The phylogenctic trees based on individual genes and the combined data suggested that Diventodon is sister to Tapiscia (Tapisciaceae) and that Dipentodon could be placed in euroside 11 of the APG system. The clade of Dipentodon and Tapiscia is closest to Malvales and Sapindales. Such finding does not support the previously suggested close relationship between Dipentodon and various other groups, including Celastraceae, Samydaceae, Flacourtiaceae, Hamamelidaceae, and Santalales.

S-RNase-mediated gametophytic self-incompatibility is ancestral in eudicots.

The evolutionary relationship between self-incompatibility systems in different families of flowering plants has long been a topic of interest. Physiological differences in the mode of gene action and the enormous sequence differences between genes with different modes of action suggest that many instances of self-incompatibility have arisen independently. In contrast, previous analyses of the S-RNase associated with gametophytic self-incompatibility in the eudicot families (Solanaceae, Scrophulariaceae, and Rosaceae) have suggested that sequences within families form well-supported and distinct lineages. In this study we demonstrate that in fact, S-RNase-mediated gametophytic self-incompatibility evolved only once in the eudicots.

Melastomeae come full circle: biogeographic reconstruction and molecular clock dating.

Rhexia, with 11 species in the Coastal Plain province of North America, is the only temperate zone endemic of the tropical eudicot family Melastomataceae. It is a member of the only pantropical tribe of that family, Melastomeae. Based on the chloroplast gene ndhF, we use a fossil-calibrated molecular clock to address the question of the geographic origin and age of Rhexia. Sequences from 37 species in 21 genera representing the tribe's geographical range were analyzed together with five outgroups. To obtain better clade support, another chloroplast region, the rpl16 intron, was added for 24 of the species. Parsimony analysis of the combined data and maximum-likelihood analysis of ndhF alone indicate that the deepest split is between Rhexia plus its sister group, a small Central American genus, and all other Melastomeae. Old World Melastomeae are monophyletic and nested within New World Melastomeae. Although likelihood-ratio tests of clock and nonclock substitution models for the full or moderately pruned datasets rejected the clock, these models yielded identical topologies (for 30 taxa) with few significantly different branch lengths as assessed by a Student's t-test. Age estimates obtained were 22 million years ago (Mya) for the divergence of Rhexia from its sister group, 12 Mya for the dispersal of Melastomeae from the New World to West Africa, and 1 Mya for the diversification of Melastoma in Southeast Asia. The only other genus of Melastomeae to have reached Southeast Asia from Africa or Madagascar is Osbeckia. The age and geographic distribution of fossils, which come from Miocene sites throughout Eurasia, suggest that Melastomeae once ranged from Eurasia across Beringia to North America from whence they reached South America and subsequently Africa and Southeast Asia. Climate deterioration led to their extinction in the Northern Hemisphere, with Rhexia possibly surviving in Coastal Plain refugia.

Phylogeny of the Eudicots: A Nearly Complete Familial Analysis Based on rbcL Gene Sequences

A phylogenetic analysis of 589 plastid rbcL gene sequences representing nearly all eudicot families (a total of 308 families; seven photosynthetic and four parasitic families are missing) was performed, and bootstrap re-sampling was used to assess support for clades. Based on these data, the ordinal classification of eudicots is revised following the previous classification of angiosperms by the Angiosperm Phylogeny Group (APG). Putative additional orders are discussed (e.g. Dilleniales, Escalloniales, Vitales), and several additional families are assigned to orders for future updates of the APG classification. The use of rbcL alone in such a large matrix was found to be practical in discovering and providing bootstrap support for most orders. Combination of these data with other matrices for the rest of the angiosperms should provide the framework for a complete phylogeny to be used in macro-evolutionary studies.