NICKRENT, DANIEL L.1*, ALBERT BLARER2, YIN-LONG QIU2,3, DOUGLAS
E. SOLTIS4, and MICHAEL ZANIS4. 1Department of Plant Biology and
Center for Systematic Biology, Southern Illinois University, Carbondale,
IL, USA 62901-6509; 2Institute of Systematic Botany, University
of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland; 3Department
of Biology, University of Massachusetts, Amherst, MA 01003-5810;
4Department of Botany, Washington State University, Pullman, WA
99165-4236. - Paleoherb Status of Hydnoraceae Supported by Multigene
Utilization of molecular phylogenetic information over the past decade has resulted in clarification of the position of most angiosperm orders, as demonstrated by the classification produced by the Angiosperm Phylogeny Group. A group of 11 families was listed at the beginning of the APG classification because "they belong neither in any of the phylogenetically basal orders at the beginning nor in the monocots or eudicots." The phylogenetic positions of most of these families (e.g. Amborellaceae, Nymphaeaceae, Winteraceae, etc.) have since been clarified, however, the positions of two holoparasitic families, Hydnoraceae and Rafflesiaceae, have remained enigmatic. To address the question of phylogenetic position of Hydnoraceae, nuclear SSU and LSU rDNA and mitochondrial atp1 and matR sequences were obtained for Hydnora and Prosopanche. These sequences were used in a combined analysis that included the above four genes as well as chloroplast rbcL and atp (these plastid genes are mising in Hydnoraceae and were hence coded as missing). Three data sets were analyzed using maximum parsimony: 1) 3 genes/461 taxa; 2) 5 genes/77 taxa; and 3) 6 genes/38 taxa. All of these analyses support the monophyly of Hydnoraceae and the association of that clade with the "paleoherb" families Aristolochiaceae and Lactoridaceae. These results suggests that either Aristolochiaceae are paraphyletic or that Hydnoraceae should be included (along with Lactoridaceae) in a more broadly defined family Aristolochiaceae. In contrast to most traditional classifications, molecular phylogenetic analyses do not suggest a close relationship between Hydnoraceae and Rafflesiaceae s. lat.
GARCIA, MIGUEL A.*, ERICA H. NICHOLSON, and DANIEL L. NICKRENT.
Department of Plant Biology, Southern Illinois University, Carbondale,
IL 62901-6509. - Intra-individual variation in plastid rDNA sequences
from the holoparasite Cynomorium (Cynomoriaceae).
It is now generally recognized that intraspecific variation in cpDNA is relatively common; however, less is known about plastid genome variation within individuals. cpDNA chimeras (plants with different cpDNA genotypes) are well-known from variegated cultivars and may result from biparental inheritance or somatic mutations. We document here an example of intra-individual variation in plastid rDNA in a wild species, Cynomorium coccineum, a nonphotosynthetic holoparasite. PCR amplifications of all portions of the ribosomal DNA cistron (16S, 23S, 4.5S, 5S and intervening spacers) were made. The PCR products were cloned and the inserts sequenced from 19 colonies. Sequence variation has been observed for all portions of the cistron, however, we will here focus on variation in the large-subunit (LSU, 23S) rDNA which is 2.7 kb in length. Of the 19 clones, five distinct types were identified. Fifteen of the sequences were nearly identical (11 differences or less) and these were designated Type I. The remaining types (II-V) were each represented by a single clone and differed from Type I by 90-235 changes. Of the five types, Type I sequences were the most derived when compared with a tobacco outgroup sequence (range across Types 250-370 differences). Higher-order structures were constructed for representatives of the five Types to address questions of functionality. Major structural changes (mainly multiple base deletions relative to tobacco) were noted in the variable regions V2, V6, V12, V15, and V16. These deletions varied in size, and those of lesser magnitude retained sequences that were alignable with tobacco. Relatively few mutations were seen in the peptidyl transferase loop, thus suggesting retention of functionality. Given that the PCR products were obtained from total genomic DNA, it is not presently known whether heteroplasmy in Cynomorium derives from variation among cpDNAs of different plastids, cells or tissues within the individual plant.
WOLFE, ANDREA D.1*, CHRISTOPHER P. RANDLE1, and KIM E. STEINER2.
1Department of EEOB, The Ohio State University; 2Department of
Botany California Academy of Sciences. - Phylogeny and biogeography
of Orobanchaceae reconstructed from nuclear rDNA 5.8s and ITS
Orobanchaceae, as recently redefined, has 88 genera and ca. 1530 species. Most taxa are distributed in temperate regions of the world with the highest density of genera and species in the northern hemisphere and in Old World floristic regions. We sequenced the nuclear rDNA 5.8s and ITS regions from 29 parasitic and six nonparasitic genera from Lamiales to reconstruct the phylogeny of Orobanchaceae. Our sampling included all of the major parasitic genera and several of the smaller genera from throughout the range of distribution. The ITS phylogeny supports the monophyly of Orobanchaceae with Lindenbergia as the basal lineage. Genera with distributions in southern and eastern Africa are located in the most derived position of the tree. The topology of the ITS tree suggests an origin of Orobanchaceae in Asia with subsequent migration of elements to North America and the Mediterranean region via the Tethyan seaway, followed by dispersal to northeastern Africa and a secondary diversification of genera throughout the southern hemisphere.
RANDLE, CHRISTOPHER P.* and ANDREA D. WOLFE. Ohio State University,
Department of Evolution Ecology and Organismal Biology, 1735 Neil
Ave., Columbus OH 43210. - Molecular evolution of photosynthetic
genes in holoparasites Harveya Hook. and Hyobanche L. (Orobanchaceae).
Harveya Hook. (Orobanchaceae) is a genus of holoparasitic plants comprised of 25-40 species inhabiting southern Africa. Genes encoding photosynthetic proteins are expected to experience increased rates of mutation in holoparasites due to the relaxation of functional constraints on these genes. Hyobanche L., the sister genus of Harveya, has undergone rbcL pseudogene formation while species of Harveya have not. Two hypotheses may be invoked to explain the absence of an rbcL pseudogenes in Harveya. (a) The loss of Rubisco functionality has occurred via a different pathway in Harveya than rbcL pseudogene formation. (b) Rubisco retains function in Harveya, in facultative photosynthesis or an unknown, non-photosynthetic role. The gene encoding the small subunit of Rubisco, rbcS, has not been examined for loss of function in holoparasites. In this study, the evolution of Rubisco was examined by nucleotide sequencing of rbcL and rbcS, and detection of the RNA (RT-PCR) and protein products (by means of Western blot) of these genes in Hyobanche and Harveya. Structural motifs of the 3' and 5'untranslated regions (UTRs) of rbcL may be important in promoting transcription. These were sequenced and analyzed for structural alterations which may prevent transcription of this gene.
OLMSTEAD, RICHARD1* and DIANE FERGUSON2. 1Department of Botany,
University of Washington, Seattle, WA 98195; 2Dept of Biological
Sciences, Louisiana State University, Baton Rouge, LA 70803. -
A molecular phylogeny of the Boraginaceae/Hydrophyllaceae.
We conducted a molecular phylogenetic study of the Boraginaceae and Hydrophyllaceae using the chloroplast genes rbcL and ndhF and including 90 species previously assigned to the two families. Results indicate that most of the taxa assigned to these families together form a monophyletic group, but that neither of the two families, as traditionally circumscribed, are monophyletic. Hydrolea (Hydrophyllaceae) and Pteleocarpa (Boraginaceae) do not belong in this group and are better placed elsewhere. Two major clades are identified. The first major group includes the predominantly temperate herbaceous subfamily Boraginoideae and the genus Codon (Hydrophyllaceae; S. Africa). The other major monophyletic group includes clades that correspond roughly to subfamilies Cordioideae, Ehretioideae, and Heliotropoideae of Boraginaceae and tribes Nameae and Hydrophylleae/Phacelieae of Hydrophyllaceae. Within this second clade, the predominantly woody and tropical members of Boraginaceae (Cordioideae, Ehretioideae, and Heliotropoideae) are monophyletic and these are sister to tribe Nameae, which also contains the only woody and tropical members of Hydrophyllaceae (along with other temperate species). Pholisma, representing the small parasitic plant family, Lennoaceae in our study, is sister to Tiquilia (Ehretioideae), with which it co-occurs in the deserts of North America. The primary characteristic that distinguishes Boraginaceae from Hydrophyllaceae is the reduced number of ovules (2 per carpel). The most parsimonious interpretation of this character on our tree requires two independent reductions in ovule number, once in the ancestor of the Boraginoideae (with the characteristic nutlet fruits) and once in the ancestor of the tropical, woody clade (mostly drupes).
STEFANOVIC, SASA* and RICHARD G OLMSTEAD. University of Washington,
355325, Seattle, WA 98195, USA. - Molecular systematics of Convolvulaceae
inferred from multiple chloroplast loci.
Convolvulaceae are a large family, traditionally comprising 55 genera with some 1600-1700 species, the members of which present a rich diversity of morphological characteristics and ecological habitats. Previous efforts to systematize this diversity without a cladistic phylogenetic framework have disagreed on the circumscription of the family as well as tribal composition and relationship. In order to circumscribe the family and assess the relationships among its major lineages, a broad data set was constructed, containing representatives of all ten recognized tribes of Convolvulaceae plus representatives of putatively related families within Asteridae. This is done by using four chloroplast regions: rbcL, atpB, psbE-J operon, and trnL-F intron/spacer. The results indicate that Convolvulaceae are sister to Solanaceae, with 100% bootstrap support for each family and the clade comprising both families. Two of the three groups that have been proposed previously as segregate families, Cuscuta and Dichondreae, are nested within the Convolvulaceae in this analysis, and the third, Humbertia, is the sister to all other members of the family. The exact position of Cuscuta could not be ascertained, but some alternatives were rejected with confidence. The study identified several distinct monophyletic groups, some of which correspond to earlier ideas. Close relationships of tribes Hildebrandtieae with Cresseae and Ipomoeeae with Argyreieae (forming Echinoconieae) were confirmed. The polyphyly of Poraneae and Erycibeae is first reported in this study.
SIUC / College of Science / Parasitic Plant Connection
Last updated: 31-Aug-01 / dln