An age-old problem.

trends in plant science correspondence Release 7.0 of Mendel database Following the recent correspondence by Jens Stougaard et al. 1 , we would like to draw the attention of your readers to the latest release of the Mendel database for the nomenclature of sequenced plant genes. Mendel provides common designations for gene families across the plant kingdom, as recommended by the Commission on Plant Gene Nomenclature (CPGN). We are pleased to report the mounting of the latest release of the database, Mendel 7.0, in the traditional ACeDB format, on the USDA-ARS Center for Bioinformatics and Comparative Genomics at Cornell University’s Genome Web site (http://genome.cornell.edu/cgi-bin/WebAce/ webace?db5Mendel/), and at Stanford’s Genomic Resources site (http://genome- www.Stanford.edu/Mendel/). Mendel 7.0 is more than twice the size of its predecessor and is contemporary with EMBL/GenBank sequence databases up until February 1999. Mendel 7.0 retains the model of sorting proteins by sequence similarity that was introduced by the John Innes group under the direction of David Lonsdale. Unfortunately the John Innes group (Norwich, UK) announced in February that it could no longer support the CPGN’s Mendel database, but the CPGN wishes to express its gratitude to David and to his associates, in particular Benedict Arnold, for automating accessions to Mendel. The new release contains all protein sequences from Swiss-Prot (release 37) and includes the complete accessions of non- green algae and cyanobacteria, in addition to the ongoing coverage of higher plants and green algae. Mendel 7.0 lists many new gene family names, including those related to alcohol dehydrogenase, methyl transferases, transporters, and additional gene families of light-harvesting proteins and chloroplast open-reading frames of undetermined function. Recognizing that function does not always correspond to simple sequence similarity, we have renamed the alignment sets derived through automation as ‘product families’; the term ‘gene family’ is reserved for sets that share similarity of sequence and function, as determined by working groups. The CPGN endorses, and indeed promotes, the importance of integrating hand curation with automated sorting. With the rush to automation, several important features of the original Mendel had become lost or obscured in recent releases. A number of gene families that had been omitted from Mendel 6 include families encoding RNAs, catalase, sucrose synthase, and subunits of RNA polymerase. These are being reinstated in Mendel 7.0, along with other features, including the fields defining alleles, subgenomes and links to other databases. In addition to all other search parameters that were available in recent releases (such as plant species, gene synonyms and accession numbers from EMBL/GenBank and Swiss-Prot) another restored feature of Mendel 7.0 is the ability to search directly by gene product. Additionally, dialog boxes will be available for comments and suggestions. The CPGN is also committed to the ongoing development of the nomenclature guidelines. Within the past few months we have identified names for .200 new gene families, including a new category of temporary gene families, which are identified by a caret (e.g. Aladh1^). Some of these temporary names have been proposed by working groups or by individual scientists, whereas others are based on traditional gene names. All names will need to be reviewed publicly on the CPGN’s Web site. Names for gene families encoding components of acetyl-coenzyme A carboxylase, for example, are currently under discussion at http://mbclserver. rutgers.edu/CPGN/FattyAcid.group.html. Those names that survive will be presented for approval by the CPGN’s associated scientists. Interested members of the scientific community are invited to propose gene family names for as yet unnamed product families; suggestions should be addressed to the e-mail address below. Discussions will be posted on the CPGN Web site (http://mbclserver.rutgers.edu/CPGN/ Conversations.html), and contributors whose proposals for gene family names are adopted by the CPGN will be identified in Mendel 7.1. Finally, we are currently in discussion with the manufacturer of an excellent relational database whose web-based format has proved too slow and tedious under our test conditions. We hope to mount a later release of Mendel that will be fast, flexible and totally user friendly. Ellen M. Reardon Commission on Plant Gene Nomenclature (e-mail cpgn@mbcl.rutgers.edu; CPGN Web site: http://mbclserver.rutgers. edu/CPGN/) References 1 Stougaard, J. et al. (1999) Genetic nomenclature guidelines for the model legume Lotus japonicus, Trends Plant Sci. 4, 1360 - 1385/99/$ Ð see front matter © 1999 Elsevier Science Ltd. All rights reserved. An age-old problem We read with interest the Perspective article on the age of tropical rain forest trees 1 . Although the piece is well written and informative, there are a number of points that we think need to be clarified. First, the authors state that ‘for time estimates of between 1000 and 2000 years this technique (natural radiocarbon dating) has a 25–50% precision’, and cite an article by K.M. Goh 2 . On consulting this article, the figure turns out to have a precision of 0.25–0.50% and is for rounding off 14 C ages. This is two orders of magnitude less than the cited value 1 . Second, the authors appear to confuse what they refer to as ‘natural radiocarbon dating’ and ‘human-induced radiocarbon dating’. To our knowledge ‘bomb’ 14 C has only been used to estimate the age of trees by extrapolating growth rates 3 . In their section ‘Estimates using radioactive indicators’ the authors incorrectly cite an article on radiocarbon ages 4 as being derived from bomb 14 C tracer methods. They also refer to a 1060-year-old rain forest tree and cite the same report 4 . In fact, this tree was a conifer in an Australian transition rain forest, and 1000-year-old conifers are common throughout the world. In their abstract, the authors also state that ‘it is not clear how accurate the technique (radiocarbon-based dating) is compared with other methods’. For trees that are less than ~350-years old, historic changes in atmospheric radiocarbon, combined with measurement precision, result in relatively inaccurate dates (~6100 years). However, for trees that are .500-years old, atmospheric radiocarbon is more stable, and dates are accurate to ~650 years. In the absence of annual rings, radiocarbon dating is the only way to directly determine the age of a tree. The indirect methods that Miguel Martinez- Ramos and Elena Alvarez-Bullya refer to are useful for understanding the mean behavior of a cohort of trees. However, these techniques cannot account for trees that remain suppressed for many decades (i.e. there is no stem diameter increment), or respond to numerous canopy openings over a period of centuries, and eventually become ancient giants. Jeffrey Q. Chambers and Susan E. Trumbore * University of California at Irvine, Earth System Sciences, 204 Physical Sciences Research Facility, University of California, Irvine, CA 92697-3100, USA * Author for correspondence (tel +1 949 824 6142; fax +1 949 824 3256; e-mail setrumbo@uci.edu) October 1999, Vol. 4, No. 10