DNA isolationTo amplify theS-RNasealleles, total genomic DNAwas isolated from young leaves of each plant accord-ing to Dellaporta et al. (1983).Primers designThe aim of this procedure was to design primers withhigh probability of amplifying everyS-RNaseallelesofSolanum.To this end, primers were designed on thebasis of conserved regions (Fig. 2a) defined by thealignment ofS-RNasenucleotide sequences fromSolanum[Sc—S2,S3,S11,S12,S13andS14(DDBJ/EMBL/GenBank X56896, X56897, S69589, AF1911732, L36667 and AF232304, respectively), and St—S2(DDBJ/EMBL/GenBank X62727)].The couple of primers designed on the basis ofC2 and C3 alignment were not degenerate (Table 3)because C2 and C3 showed very high amino acidsequencesimilarityamongtheS-RNasealleles.Conversely,sincethealignmentofC1andC4exhibitedloweraminoacidsequencesimilarityamong theS-RNasealleles, primers designed on thebasis of these conserved regions were degenerate(Table 3).Nested PCR assaysTwo steps of PCR amplification were performed innested PCR assays. C1FD and C4RD primers wereused in the first round of PCR amplification. Each25ll reaction mixture contained 0.5lM of eachprimer,200lMdNTPmix,4mMMgCl ,1029PCRbuffer,2UTaqpolymerase(Invitrogen,Carlsbad,CA,USA)and150ngofDNAastemplate. The PCR program consisted of 1 cycleat 94_C for 2 min; 35 cycles at 94_C for 30 s, Table 1Argentinean accessions ofS.chacoense,S.spegazziniiandS.kurtzianumSpeciesAccessionaCollection sitebPlants used in this experimentcS.chacoensePI458314Catamarca, Poman, 28´_180S–66_090W, 1,700 m5(P1–P5), P3 carriesS11-RNasealleleQBCMBuenos Aires, Balcarce, 38_000S–57_490W, 140 m13(Q1–Q13), Q1 carriesS16-RNasealleleS.spegazziniiOL4916Salta, Cuesta del Obispo, 25_100S–65_520W, 3,300 m5(O1–O5)OKA5649Salta, Cuesta del Obispo, 25_100S–65_520W, 3,000 m5(O6–O10)S.kurtzianumOKA6003La Rioja, Sierra de Ambato, 28Æ450S–66_240W, 1,000 m5(K1–K5)CIM872Mendoza, Estancia La Cumbre, 34_100S–69_140W, 1,440 m5(K6–K10)aCollector and collection numbers; collectors:OkaOkada;OLOkada, Lucarini;CIMClausen, Masuelli;QBCMBedogni, Camadro,Marcellan´bProvince, location, coordinates, altitudecNumber, reference name in brackets andS-RNasealleles confirmed in these plants (Marcellan et al. 2006)´ Euphytica (2012) 187:19–2921123 55_C for 1 min, and 72_C for 1 min, and 1 cycleat 72_C for 10 min. Combinations of C2F–C4RDorC2F–C3RprimerswereusedtoperformthesecondroundofPCRamplification.Each25llreaction mixture contained 5ll of reaction productfrom the first round of PCR, 200lM dNTP mix,4mM MgCl ,1029PCR buffer, 2 U Taq polymer-ase (Invitrogen, Carlsbad, CA, USA) and 0.5lMof each primer. The PCR program was similar tothe first round of PCR except for the annealingtemperature(60_C).Amplifiedproductsofeachplant were separated on 2 % TAE agarose gels,stained with Sybr Safe and visualized with a blue-light transilluminator.SSCP analysesPCR products obtained with C2F and C3R nestedprimers were extracted using E-Gel_CloneWellTMSYBR Safe Gels and E-Gel_IBase˙TMPower System(Invitrogen, Carlsbad, CA, USA). For SSCP analysis5ll of each PCR fragment were added to 9llofdenaturing solution [95 % (v/v) formamide, 0.05 %(w/v) xylene cyanol, 0.05 % bromophenol blue, and0.01M NaOH], heated at 94_C for 4 min. and thenchilled on ice. The samples were loaded on 16914cm gel using a 0.59MDETM(Mutation DetectionEnhancement) gel solution (Cambrex Bio ScienceRockland Inc, USA) and were electrophoresed for 2 h Table 2Results of pollen–pistil compatibility relationships in crosses within and between QBCM and PI458314 accessionsobtained by fluorescence microscopyFemale parentMale parentQBCMPI458314Q1(S16)Q2Q3Q4Q5Q6Q7Q8Q9Q10Q11Q12Q13P1P2P3(S11)P4P5QBCMQ1 (S16)IaCbCCCCCCCCCQ2ICCCQ3CCCCCCQ4CCICCQ5CICQ6CCICQ7CCCCCCQ8CCCIQ9CCIQ10CCIIQ11ICIIICCQ12CIQ13CICIIIPI458314P1CCICICP2CCIP3 (S11)CCCCCCICP4CCCIICP5CCICCCCEach plant (heterozygous genotype) was identified with a letter and a number (reference name). The plants Q1 and P3 carryS16-andS11-RNasealleles, respectively. The number of genotypic combinations performed for each combination of plants was determined bythe synchrony of flowering and the number of flowers available per parental plantaIncompatible relationship: inhibition of growth of pollen tubes in the style. It could be visualized in Fig. 1bbCompatible relationship: normal growth of pollen tubes along pistil. It could be visualized in Fig. 1a 22Euphytica (2012) 187:19–29123
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