Phylogenetic Analysis of Chloroplast DNA Variation in Coffea L.

Transcription

1 _" MOLECULAR PHYLOGENETICS AND EVOLUTION Vol 9, No 1, February, pp ,1998 ARTICLE NO FY Phylogenetic Analysis of Chloroplast DNA Variation in Coffea L J Cros,* M C Combes,* P Trouslot,* F Anthony,+ S Hamon," A Charrier,* and P Lashermes*l *Laboratoire de Ressources Génétiques et d'amélioration des Plantes Tropicales, ORSTOM, BP 5045, F-34032, Montpelliel; France; tatl, Turrialba, Costa Rica; and $ENSAM, place Viala, F-34060, Montpelliel; France Received April 15, 1997; revised July 15, 1997 The trnlrtntf intergenic spacer of cpdna has been sequenced from 38 tree samples representing 23 Coflea taxa and the related genus PsiZanthus These se- specific hybrid&ation onvergence (Doebley, 1992; Riese- Coffee trees (family Rubiaceae) are classified in two genera, Coffea and PsiZanthus, each genus being divided into two subgenera (Bridson and Verdcourt, 1988) All Coffea species are native to the intertropical forest of Africa, Madagascar, and islands of the Indian Ocean (Mascareign and Comoro Islands), while species belonging to the genus PsiZanthus originate from either Asia or Africa The subgenus Coffea encompasses more than 80 taxa so far identified, including the two species of economic importance: Coffea arabica L and Coffea canephora Pierre (Charrier and Berthaud, 1985; Berthaud and Charrier, 1988) Coffea species are diploid (2n = 2x = 22), except C arabica (2n = 4x = 44) which is self-fertile and considered a segmental allotetraploid (Carvalho, 1952; Grassias and Kammacher, 1975) Although showing considerable variation in morphology, size, and ecological adaptation, Coffea species hybridize readily yith one another and produce relatively fertile 978; Louarn, 1993) Success in zation has even been reported (Coucation) The internal tranon of the nuclear ribosomal ssfully used to establish a molecular phylogeny of Coffea species (Lashermes et al, 1997) Nevertheless, comparisons between phylogenies inferred from both chloroplast and nuclear genomes would provide a better basis for assessing species relationships Exclusively maternal inheritance of cpdna was observed in-biterspecific hybrids between C arabica and C canephora, and in an intraspecific progeny of C canephora, suggesting that the mode of plastid inheritance in Coffea is strictly maternal (Lashermes et al, 1996) CpDNAvariation present in the subgenus Coffea was assessed by restriction fragment length polymorphism (RFLP) oqboth the total chloroplast genome and the atpb-rbcl intergenic region (Lashermes et al, 1996) Only 12 variable characters were evidenced, indicating low cpdna variation To increase the number of polymorphic markers, comparative DNAsequencing seems particularly relevant The technique is relatively fast, convenient, and offers a large data set of discrete characters The sequence of a chloroplast gene such as rbcl, which has been widely used for inferring /98 $2600 Copyright CI 1998 by Academic Press All rights of reproduction in any form reserved

2 L I, 110 CROS ET AL phylogeny in plants (Clegg and Zurawski, 19921, is likely to be changing too slowly to provide enough characterh for a phylogenetic analysis between congeneric species Recent results indicate that chloroplastic noncoding regions such as the intergenic spacer between the trnl exon and the trnf gene can be used to address questions concerning relationships among closely related species or genera (Van Ham et al, 1994; Gielly and Taberlet, 1994) Plant Material hl4"exhu AND METHODS plant material was from the ORSTOM col~ec~ion, which resulted kom expeditions in Africa and Madagascar (Anthony, 1992) The actessions -surveyed, with their origins, are hdicated in Table 1 Thirty-six accessions belonged to 23 Cofea nted by two species, l? ebracteolatus and l? studying the cpdna variatio insights into Cofea evolution ships of Coffea species inferre DNA variation are compared with estima data from the nuclear genome Coffea arabica L C betirandi Chev C brevipes Hiem C canephru Pierre c sp x C stenophylla Don FB 1 FA 21 Psilanthlwr ebrmteolatlwr Hiem OA 153

3 -,, ~,, CHLOROPLAST DNA VARIATION IN Cofea L 111 that CTAB was replaced by MATAB (mixed alkyl trimethylammonium bromide) in the extraction buffer PCR Amplification and DNA Sequencing Primers deiigned by Taberlet et al (1991) were used for PCR amplification of the trnl-trnf region (5'- GGTTCAAGTCCCTCTATCCC-3 ' and 5 '-ATTTGAAC- TGGTGACACGAG-3') The primers are constructed against distal regions of the highly conserved trna genes and thus are suitable for amplifying this noncoding region from a broad spectrum of higher plants Amplifications were,performed in a volume of 50 pl contahing 10 mh8 TrisLHC1 ph 90,01% Triton X-100, intergenic spacer (Fig 1) Alignment of coffee tree sequences reqirired the introduction of six gaps, two of which were 1 bp in length and one each of 8,11,20, and 30 bp Alignment including the outgroup species, G grandiflora, results in two additional gaps of 1 and 10 bp, respectively The nature of these gaps (insertion or deletion) was hypothesized on the basis of 'Outgroup comparison All inferred gaps in coffee tree sequences were found to be deletions except for a gap 1 bp in length which could correspondto a putative insertion The length of the trnl-trnf spacer varies between 314 (accession 14) and 343 bp in individual accessions, the multide aliment beinn 344 bp in length I, ;%,,:, : e: _i,- $i 1',

4 I " ~ _" -,, 112 CROS ET AL S1 (acces 1,2, 13,31), 52 (acces28) S3 (acces 29) 54 (acces 14) 55 (acces 17) S6 (acces 23,24,25,26,27) S7 (acces 12) 1 49 TTTGATCCCCCAACTATTTATCCTATCCCCCTTTCGTTAGCGGTTCAAA T - - S8 (acces4,5,6,7,8,9,10,11,20,33) S9 (acces 2134) S10 (acces 30) Sll (acces 32) SI2 (acces 18,,19) 513 (acces 35,36) T S14 (acces'l6) T,: S15 (acces 22) S16 lacces 3) -----_- 517 (acces 15) 518 (acces 38 ie P mannir? S19 (acces 37 ie P ebrac!eolatus) 520 (acces 39 ie Ggrandflora) T SI AAACCTTATTCATTTACTCTATTCTCTTAGAAATCGATCGATCT~ACGG~GCCCTTTTCTTATCA~TCTTGTGTT s S8 _ s9 s10 _- Sll T T 514 _ T s15 S16 _ 517 S18 _ --_----- S19 S20 T A,, TGG " ( : T' T, T T ' s1 s2 s3 s s7 S8 S9 s10 s S13 S14 S15 S16 s17 S18 s19 s ATTTATGATATAC c c CT T G G T C c FIG 1 Aligned nucleotide sequences of the intergenic spacer between the trnl (UM) 3'exon and the trnf (GAA) gene (see Table 1 for accession code) Dashes denote alignment gaps and dots denotes bases in common with the first sequence The arrow indicates the begimiing of trnf (GAA) The -35 and - 10 promoter elements are overligned

5 ~ f ---_ ~ * _ I I - CHLOROPLAST DNA VARIATION IN Corea L 113 I s1 s2 s3 s4 ss 56 SI S8 s9 s10 Sll s s11 S18 S19 s ATACTGAAACTTACAAAGTACTCTTTTTTAAGATACAAGATA~GAAA~CTAGTACCTAGAT~TTTTGTAAGATACAATCCCCTTTC c c _-_- c c I c c c c C CGC C CCGC c c, c c c c c c C A c c c c s tmf gene 361 CTTCTTTTAATTGACATÁG- CCCCCCTTTT~CAT~TGA~ATGCTACATTGGGACTGGTCGGGATAGCTCAGAT 52 I s3 :: _--_--- SS S6 :, I,,s7 -- S8 :, _ SlO -, s11 kig 1

6 114 CROS ET AL cì4 sa s14 s22 s23 s25 ' r5 I I I I I P mannii1 wc wc -l-c ' humblofiana 1 FIG 2 One of the most parsimonious trees (97 found) derived from parsimony analysis of cpdna polymorphism Characters appearing only once on the tree are solid boxes; parallel and reversal changes are designated with open boxes The characters code$ rl to rll, dl to d6, and sl to s25 correspond to restriction site changes of cpdna, indels, and nucleotide substitutions on the tmum$' intergenic spacer, respectively Numbers below branches are bootstrap values (100 replicates) Clades present in the strict consensus topology are indicated by grey lines The letters following each clade indicate the geographical distribution of the relevant species: W (west Afi-ica), WC (west and central Africa), C (central Africa), E (east Africa), and M (Madagascar and the Comoro Islands),, ' I

7 I, CHLOROPLAST DNA VARIATION IN Cofeu L 115, : i i i :, I,,_, ;!,t _ ',, : ; ' I, & ' i _ (

8 116 GROS ET A+: and :Chakrier, k (1997) species (Cofea L) as jribosomal DNA Theor last DNA in the genus &er, A (1993) Use of i, D E (1991) Phylogenetic consequences in plants Evol Den& Plants 5: tics5: , : ' ' Grant, V (1971) "Plant Speciation," Columbia Univ Press, New York primers for aniplification of three non-coding regions of chloroplast DNA Plunt Mol Biol 17:

9 c 1 - c î i T 1 F Van Ham, R C H J, Hart, H, Mes, TH M, and Sandbrink, JM (1994) Molecular evolution of noncoding regions of the chloroplast t - genome in the Crassulaceae and related species Cum Genet, i i L I Wendel, J F, and Albert, V A (1992) Phylogenetics of the cotton genus (Gossypjum): Character-state weighted parsimony analysis of chlorop1ast;dna restriction site data and its systematic and bicgeographic implications Syst Bot 1% CHLOROPLAST DNA VARUTION IN Coffea L ' 1171 Wolfe, K H, Li, W H, and Sharp, P M (1987) Rates of nucleotide substitution vary greatly among plant mitochondrial, chloroplast, and nuclear DNAs Proc Natl Acad Sci USA 84: 905d-9058 ZUraWSki, G2 and Clegg, M- T (1987)- Evolution of higher-plat chloroplast DNA-encoded genes: implications for structure-function and phylogenetic studies Annu Rev Plant Physiol 38: