Dataset Information

Parallel evolution of storage roots in morning glories (Convolvulaceae).

ABSTRACT: BACKGROUND:Storage roots are an ecologically and agriculturally important plant trait that have evolved numerous times in angiosperms. Storage roots primarily function to store carbohydrates underground as reserves for perennial species. In morning glories, storage roots are well characterized in the crop species sweetpotato, where starch accumulates in storage roots. This starch-storage tissue proliferates, and roots thicken to accommodate the additional tissue. In morning glories, storage roots have evolved numerous times. The primary goal of this study is to understand whether this was through parallel evolution, where species use a common genetic mechanism to achieve storage root formation, or through convergent evolution, where storage roots in distantly related species are formed using a different set of genes. Pairs of species where one forms storage roots and the other does not were sampled from two tribes in the morning glory family, the Ipomoeeae and Merremieae. Root anatomy in storage roots and fine roots was examined. Furthermore, we sequenced total mRNA from storage roots and fine roots in these species and analyzed differential gene expression. RESULTS:Anatomical results reveal that storage roots of species in the Ipomoeeae tribe, such as sweetpotato, accumulate starch similar to species in the Merremieae tribe but differ in vascular tissue organization. In both storage root forming species, more genes were found to be upregulated in storage roots compared to fine roots. Further, we find that fifty-seven orthologous genes were differentially expressed between storage roots and fine roots in both storage root forming species. These genes are primarily involved in starch biosynthesis, regulation of starch biosynthesis, and transcription factor activity. CONCLUSIONS:Taken together, these results demonstrate that storage roots of species from both morning glory tribes are anatomically different but utilize a common core set of genes in storage root formation. This is consistent with a pattern of parallel evolution, thus highlighting the importance of examining anatomy together with gene expression to understand the evolutionary origins of ecologically and economically important plant traits.

SUBMITTER: Eserman LA

PROVIDER: S-EPMC5975488 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Parallel evolution of storage roots in morning glories (Convolvulaceae).

Eserman Lauren A LA Jarret Robert L RL Leebens-Mack James H JH

BMC plant biology 20180529 1

<h4>Background</h4>Storage roots are an ecologically and agriculturally important plant trait that have evolved numerous times in angiosperms. Storage roots primarily function to store carbohydrates underground as reserves for perennial species. In morning glories, storage roots are well characterized in the crop species sweetpotato, where starch accumulates in storage roots. This starch-storage tissue proliferates, and roots thicken to accommodate the additional tissue. In morning glories, stor ...[more]

PMID: 29843615

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Project description:A new morning glory, Calystegia felixProvance & A.C. Sanders sp. nov. (Convolvulaceae), is described from the Los Angeles, San Gabriel, and Santa Ana River basins. Historical collections of the species, which prior to 2011 had not been seen alive in 94 years, have been misidentified as Calystegia sepium (L.) R. Br. subsp. binghamiae (Greene) Brummitt. The undescribed species was rediscovered in the City of Chino in April of 2011, a few miles north of the location where the most recent previous collection had been made by I. M. Johnston in 1917. The plants were found just prior to their likely destruction by grading and trenching for an underground power line. Intensive searches have resulted in the discovery of five additional occurrences, all of them in the City of Chino. Calystegia felix is at high risk of soon becoming extinct in the wild. All of the known extant occurrences are associated with well-watered landscaping on recently completed industrial, commercial, and residential developments. Every known living occurrence is within the limits of a ciénega belt, which is now mostly historical. Otherwise, the new species is only known only from collections made around the turn of the 20(th) century in what are now heavily urbanized areas, including one from South Los Angeles and another from Pico Rivera in Los Angeles County. Calystegia felix lacks the large bracts that immediately subtend, and enclose the calyx, which are always present in members of the Calystegia sepium complex. Affinities to Calystegia felix are found among other western US species with graduated sepals and small, often somewhat remote bracts. We discuss the enduring confusion between Calystegia felix and Calystegia sepium subsp. binghamiae, and differentiate the new species from some of its more likely relatives. The taxonomic treatment is supplemented by photos of herbarium specimens and living plants. We also discuss the ecological setting of Chino's ciénega belt, which was a mosaic of palustrine wetlands.

Project description:BACKGROUND: The genus Cuscuta L. (Convolvulaceae), commonly known as dodders, are epiphytic vines that invade the stems of their host with haustorial feeding structures at the points of contact. Although they lack expanded leaves, some species are noticeably chlorophyllous, especially as seedlings and in maturing fruits. Some species are reported as crop pests of worldwide distribution, whereas others are extremely rare and have local distributions and apparent niche specificity. A strong phylogenetic framework for this large genus is essential to understand the interesting ecological, morphological and molecular phenomena that occur within these parasites in an evolutionary context. RESULTS: Here we present a well-supported phylogeny of Cuscuta using sequences of the nuclear ribosomal internal transcribed spacer and plastid rps2, rbcL and matK from representatives across most of the taxonomic diversity of the genus. We use the phylogeny to interpret morphological and plastid genome evolution within the genus. At least three currently recognized taxonomic sections are not monophyletic and subgenus Cuscuta is unequivocally paraphyletic. Plastid genes are extremely variable with regards to evolutionary constraint, with rbcL exhibiting even higher levels of purifying selection in Cuscuta than photosynthetic relatives. Nuclear genome size is highly variable within Cuscuta, particularly within subgenus Grammica, and in some cases may indicate the existence of cryptic species in this large clade of morphologically similar species. CONCLUSION: Some morphological characters traditionally used to define major taxonomic splits within Cuscuta are homoplastic and are of limited use in defining true evolutionary groups. Chloroplast genome evolution seems to have evolved in a punctuated fashion, with episodes of loss involving suites of genes or tRNAs followed by stabilization of gene content in major clades. Nearly all species of Cuscuta retain some photosynthetic ability, most likely for nutrient apportionment to their seeds, while complete loss of photosynthesis and possible loss of the entire chloroplast genome is limited to a single small clade of outcrossing species found primarily in western South America.

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Dataset Information

Parallel evolution of storage roots in morning glories (Convolvulaceae).

Publications

Parallel evolution of storage roots in morning glories (Convolvulaceae).

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