New reports of nuclear DNA content for 66 traditional Chinese medicinal plant taxa in China

Abstract

The amount of DNA in the unreplicated haploid nuclear genome (C-value) provides important information for genome biodiversity. Genome size is used in a strikingly wide variety of plant biological fields with both practical and biological significance. To extend previously published datasets on plant nuclear content and to compile information on the DNA content of traditional Chinese medicinal plants in China, flow cytometry (FCM) was used to estimate C-values of medicinal plants in Shaanxi province, China. A total of 80 medicinal plant species and vouchers were collected from locations across Shaanxi province in China. Nuclei were extracted from fresh leaves in one of two buffers, stained with fluorochrome propidium iodide (PI), and analyzed on a Guava flow cytometer to measure the position of the fluorescence peaks relative to those of an internal calibration standard. Replicate extractions, low coefficients of variation and comparisons with published C-values in the same and related species were used to confirm the accuracy and reliability of our results. Prime C-values for 66 medicinal plant taxa are provided for which no published data exist, comprising 66 angiosperms, one gymnosperm and one pteridophyte. C-values for 14 additional taxa where a genome size has previously been published are also provided. The prime values represent new reports for 27 genera (out of the 48 genera and 38 families sampled). These data provide the foundation to enable phylogenetic analysis of C-value variation and karyotype diversity in Chinese traditional medicinal plants and assist future analyses aimed at analyzing how C-values co-vary with effective components and functional traits in Chinese traditional medicinal plants.

Keywords:

• C-value
• traditional Chinese medicinal plant
• flow cytometry
• plant phylogenetics

Acknowledgments

This work was partially funded by Natural Science Foundation of China (No. 31100241), Shaanxi science and technology plan projects (2011K16-02-05), Xi’an key scientific and technological project (NC1116 (1)) and Innovation funds of graduate programs, SNNU (2013CXS017). The authors thank Dr. Leitch IJ (Royal Botanic Gardens, UK) for her kind revisions on the manuscript.

Appendix. Table A1. C-values of 80 Chinese traditional medicinal plants.

Table

The format of this table is modified from that used by Bennett and colleagues (Bennett and Leitch 1997, 2011; Bennett et al. 2000; Zonneveld et al. 2005 – see main text for references). Notes on its structure are as follows.

• “New” reports at specific and generic levels. Taxa with C-values first reported here (i.e. for which no previous C-value has been published for this species; Bennett and Leitch 2012) are indicated with “+” and appear in bold text; “+ +” indicates that the C-value also is the first report for the genus; “–” indicates that at least one C-value for the taxon has already been published.

• Taxa. Names of taxa correspond generally to those provided in the Flora Republicae Popularis Sinicae (http://frps.plantphoto.cn/) and the Directory of Chinese medicinal plants.

• Family, order, and class. The family and order assigned to angiosperms correspond with assignments under the Angiosperm Phylogeny Group system (APG III 2009; Stevens 2012). Dic = dicotyledoneae; Mon = monocotyledonae; Equ = Equisetopsida; Lep = Leptosporangiopsida; Taxus = Taxopsida.

• Life cycle types. Information on the type of life cycle for each taxon was gleaned from the literature or from www.plants.usda.gov/classification.htm: A = annual; B = biennial; P = perennial; AP = annual–perennial (including annual–biennial); BP = biennial–perennial.

• DNA amounts and conversion factors. 1C-values were calculated from the available 2C-values. For 1C-values given in megabase pairs (Mbp), we used the conversion factor of 1 pg = 978 Mb (Doležel et al. 2003).

• Buffers. We relied primarily on the Otto and LB01 isolation buffers (Doležel et al. 1989; Otto 1990; Doležel and Gohde 1995) using the methods (reagent preparation, selection of standards, etc.) laid out initially by Otto (1990) and available on the flow cytometry methodology webpage (www.ibot.cas.cz/fcm/method.html).

• Vouchers. This study is part of a larger Diversity of Medicinal Plants (DMB) project at the Shaanxi Normal University (SNNU). To permanently document the taxonomic identity of the source material, and to serve as a reference point for future changes in determinations or nomenclature, we collected herbarium vouchers and deposited these at the herbarium in SNNU.