Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer
-
Upload
university-of-adelaide -
Category
Technology
-
view
2.210 -
download
1
description
Transcript of Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer
![Page 1: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/1.jpg)
The Environment InstituteWhere ideas grow
Richard Abbott
Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer
![Page 2: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/2.jpg)
Plant Introductions & Evolution:Hybrid Speciation and
Gene Transfer
Richard Abbott - St Andrews University, UK
![Page 3: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/3.jpg)
“…invasive species cost the British economyapproximately £2bn a year…”
“…approximately 15% of the aliens within Europeare known to have some impact on the environment or economy - and this problem goes across all taxonomic groups."
“There are almost 11,000 alien species inEurope and the trend of new arrivals isshowing no signs of levelling out.”
“Invasive species are one of the greatest threats facing biodiversity today.”
BBC News 13 October 2008
![Page 4: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/4.jpg)
Plant Introductions- points of entry
![Page 5: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/5.jpg)
Level of Plant Invasion in Europe
(% aliens)
Chytry et al. (2009) Diversity & Distributions.15: 98-107
![Page 6: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/6.jpg)
Plant Species in Britain & Ireland(after Preston et al. 2002)
Total Number of Species 2711
Native 1363 (50.28%)
Native/Alien* 44 (1.62%)
Naturalised Aliens* 1304 (48.10%)
* Species introduced after AD 1500
![Page 7: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/7.jpg)
Invasives are models for studying
(i) Evolution in response to environmental change
(ii) Speciation and Gene transfer following hybridization with other species
EVOLUTIONARY CONSEQUENCESOF INVASIONS
![Page 8: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/8.jpg)
Hybrid speciationSpecies BSpecies A
F1 hybrid
X
2n=10 2n=10
2n=10
2n=10
Homoploid hybrid species
2n=20
Chromosomedoubling
Allopolyploid species
![Page 9: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/9.jpg)
Origin of a new homoploid hybridspecies - Senecio squalidus
Oxford Ragwort (Senecio squalidus)
![Page 10: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/10.jpg)
Oxford Ragwort (Senecio squalidus) in the UK
Brought to Oxford Botanic Gardens from Mount Etna, Sicily, 1700
Escaped and spread around UK via railway network
![Page 11: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/11.jpg)
The Senecio hybrid zone on Mount Etna, Sicily.
Senecio aethnensis
Senecio chrysanthemifolius
Hybrid zone
3000m
1000m
2000m
0m
![Page 12: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/12.jpg)
Morphological differences between S. chrysanthemifolius and S. aethnensis
Leaf shape and texture Flower head size
![Page 13: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/13.jpg)
Differences between S. squalidus and its Sicilian relatives
Intermediate morphology - distinct from wild hybrids on Mt. Etna
Urban habitats: railways, walls, motorways
![Page 14: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/14.jpg)
Resolved:
2600 m
13 markers diagnostic of S. aethnensis
150 m
13 markers diagnostic of S. chrysanthemifolius
Surveyed RAPD variation for species diagnostic markers
![Page 15: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/15.jpg)
Ancestry of S. squalidusplants in UK
Ancestry of plants alongaltitude gradient, Mt Etna
2600 m
150 m
James JK, Abbott RJ (2005)Evolution 59: 2533-2547
![Page 16: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/16.jpg)
PCo 1 (40.6%)
PCo
2 (1
0.3%
)
S. chrysanthemifolius Hybrids S. aethnensis S. squalidus
Principal Coordinate Plot – RAPD Variation
James JK, Abbott RJ (2005)Evolution 59: 2533-2547
![Page 17: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/17.jpg)
HYBRID ORIGINS OF NEW TAXA IN SENECIO
1792
S. aethnensis x S. chrysanthemifolius(2n=20) (2n=20)
S. squalidus(2n=20)
![Page 18: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/18.jpg)
Species B
F1
Bc1
Bc2
Species A
Bc3
Bc4
25% B
50% B
12.5% B
6.25% B
3.12% B
Introgression - Gene Transfer
Movement of genes fromone species to anotherby recurrent backcrossingof hybrid to a parent
![Page 19: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/19.jpg)
Introgression (Gene transfer):
• Many examples based on analyses of neutral markers
• Very few examples involve genes affecting fitness
• Few examples where hybridizing species differ in ploidy and/or mating system
![Page 20: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/20.jpg)
Hybridizes with native Groundsel (S. vulgaris)
Oxford Ragwort (Senecio squalidus)
![Page 21: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/21.jpg)
2n = 20
2n = 40
X
F1(2n = 30)
sterile
S. vulgaris S. squalidus
Self-compatible Self-incompatible
![Page 22: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/22.jpg)
Effects of interspecific hybridization on gene expression
S. vulgarisS. x baxteriS. squalidus
0.1
1.0
10
Nor
mal
ised
Exp
ress
ion
(Log
Sca
le)
S. squalidus F1 S. vulgaris
‘Transcriptome shock’ in F1 hybrid. Normalized microarray expression data for 475 cDNA clones identified as showing significant differences in expression between F1 and one or both progenitors. Hegarty et al. (2005) Molecular Ecology 14: 2493-2510
![Page 23: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/23.jpg)
(2n=20) (2n=40)
S. squalidusWaste-sites, Roadsides,
Walls
S. vulgarisAgricultural land
Waste-sites,Gardens
X
Hybrid evolution in Senecio
New Products
S. eboracensis (2n=40)Only in York
1979
S. cambrensis (2n=60)N.Wales & Edinburgh
1948
Radiate S. vulgaris (2n=40)Widespread in UK
1832
![Page 24: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/24.jpg)
Radiate Groundsel (S. vulgaris var hibernicus )
![Page 25: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/25.jpg)
Outcrossing rates of Non-Radiate (NN) and Radiate (RR) plants
Outcrossing rates
Non-Radiate Radiate
1 - 15% 6 - 36%
![Page 26: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/26.jpg)
Finding genes that produce ray florets
• QTL analysis
• Microarray analysis
• Candidate gene approach √
![Page 27: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/27.jpg)
Ray floret
Disc floret
![Page 28: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/28.jpg)
CYCLOIDEA AS A CANDIDATE GENE
Snapdragon(Antirrhinum majus)
1 gene is largely responsible for change in flower shape: Cycloidea
Encodes a transcription factor
Luo et al. (1996) Nature 383: 794-9Luo et al. (1999) Cell 99: 367-76
![Page 29: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/29.jpg)
• 6 cycloidea-like genes (RAY1-6) amplified in S. vulgaris
• 2 (RAY1 and RAY2) expressed in outer floret primordia
![Page 30: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/30.jpg)
![Page 31: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/31.jpg)
Semi-quantitative RT-PCR showing RAY1 and RAY2expression in young flower heads of RR and NN S. vulgaris
![Page 32: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/32.jpg)
RAY Cleaved Amplified Polymorphic Sequences (CAPS)
Taq1 digest EcoR1 digest
• Linkage analysis: No recombinants for RAY1 or RAY2found among >700 F2 offspring of R/R x N/N cross
• Linkage confirmed by bulk segregant analysis of R/Rand N/N genotypes: in each case no recombinantsfound among 2,800 chromosomes
• RAY1 and RAY2 are tightly linked and associated with RAY
![Page 33: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/33.jpg)
DNA sequences of RAY1 and RAY2 genes associated with flower head forms
N and N1 - Non-radiate sequencesR and R1 - Radiate sequences
Radiate S. vulgaris contains the R sequence found in S. squalidus
Confirms Radiate S. vulgaris received the R sequence from S. squalidus
![Page 34: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/34.jpg)
Transformation studiesDo the RAY1 and RAY2 genes control development
of ray florets in S. vulgaris flower head?
• Developed transformation system for S. vulgarisusing Agrobacterium tumefaciens strain GV3101 and a Kanamycin resistance screen
• Took sequences of RAY1 and RAY 2 genes fromNon-radiate S. vulgaris (i.e. N alleles) andinserted them with 35S constitutive promoterinto Radiate S. vulgaris
RAY1
RAY2
![Page 35: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/35.jpg)
Transformants
‡ Expression of RAY2 N allele in Radiate S. vulgaris produces tubular ray florets
Both genes, RAY1 and RAY2, affect ray floret development
* Expression of RAY1 N allele in Radiate S. vulgaris inhibits ray floret production
Kim et al. (2008) Science 322: 1116-1119
Control * ** ‡
![Page 36: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/36.jpg)
Conclusions
• We have isolated two genes RAY1 and RAY2 that control the development of ray florets in the flower heads of Senecio vulgaris
• Radiate alleles of RAY1 and RAY2 are tightly linked and were introgressed from the diploid S. squalidus to generate the radiate variant of S. vulgaris
• Radiate S. vulgaris has a greater outcrossing rate than the non-radiate variant
• This difference in outcrossing rate between the two morphs of S. vulgaris will affect their relative fitness in polymorphic populations
![Page 37: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/37.jpg)
0.01
RAY2b-ARAY2b-C
RAY2b-BRAY2a-R
RAY2a-NRAY2a-NaRAY2a-R2
RAY2a-R2aRAY2a-R1RAY2a-R1a
100
100
100
100
68
60
Clade 2(RAY2a)
Clade 1(RAY2b)
Maximum likelihood phylogeny ofRAY2 sequence variation
Chapman & Abbott (2009) New Phytologist
• Clades 1 and 2 represent two copies of RAY2 gene (RAY2a and RAY2b)
• Both copies are found in S. vulgaris (tetraploid). Diploids contain only RAY2a
![Page 38: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/38.jpg)
Distribution of RAY2a-Rand R1 alleles in S. squalidus
Note: Only the ‘R’ allele has been introgressed into radiate S. vulgaris
Chapman & Abbott (2009) New Phytologist
Guildford
SouthamptonExmouth
Oxford
Birmingham
ManchesterLeeds
Edinburgh
Aberdeen
Key:R R1
0%
20%
40%
60%
80%
100%
NIC1(755m)
RAN1(755m)
MON1(1045m)
SAP4(1364m)
SAP2(1613m)
SAP0(1915m)
PRO2(2061m)
ET3(2287m)
R
R2
R1
Relative frequencies of RAY2a alleles in Senecio populations on Mount Etna
![Page 39: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/39.jpg)
HYBRID ORIGINS OF NEW TAXA IN SENECIO
x S. vulgaris(2n=40)
S. baxteri(2n=30)
x S. vulgaris(2n=40)
S. vulgaris (Radiate)(2n=40)
1832
S. eboracensis(2n=40)
19791792
S. aethnensis x S. chrysanthemifolius(2n=20) (2n=20)
S. squalidus(2n=20)
S. cambrensis(2n=60)
1948
![Page 40: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/40.jpg)
Acknowledgements:
St Andrews University: John Innes Centre:
Mark Chapman Rico CoenAmanda Gillies Pilar CubasJuliet James Min-Long Cui
Minsung Kim
Funded by NERC & BBSRC
Andy Lowe
![Page 41: Plant Introductions & Evolution: Hybrid Speciation and Gene Transfer](https://reader034.fdocuments.in/reader034/viewer/2022051816/5465c543af79596f338b4ec3/html5/thumbnails/41.jpg)
The Environment InstituteWhere ideas grow
www.adelaide.edu.au/environmentPhone: +61 8 8303 5379