The document summarizes a seminar presentation on mapping traits in carrots, including carotenoids and root system architecture. It describes using genotyping-by-sequencing and RNA-Seq to identify genes associated with carotenoid accumulation. Candidate genes were identified on chromosomes 5 and 7 linked to lutein and beta-carotene levels, respectively. The presentation also discusses using 2D imaging software to measure root system architecture traits in a mapping population, and finding genomic regions linked to economically important root traits.
2. • Introduction to carrots and their domestication history
• Traits we are interested in mapping
• Carotenoids
• Root System Architecture (RSA)
• Part I - Utilizing Genotyping-by-Sequencing (GBS) and
RNA-Seq to identify carotenoid traits of interest
• Part II – Utilizing 2D imaging to identify RSA traits
• Ongoing work and future directions
3. • Carrots are the 7th most economically
important vegetable crop in the United States
• The majority of carrot consumption is fresh market
• In 2014, on average, one person consumed 8.5lbs
(~4kg) of carrots
• Total production was valued at almost 700 million
US dollars (2.3 trillion COP) in 2013, up from 550
million in 2004
• California produces 85% of all carrots grown in the
U.S.NASS, 2014
4. • Historical
• Pre-900s purple and yellow carrot varieties
in Afghanistan and surrounding vicinity
• 1100 AD domesticated carrots moved into
SW Europe
• European cultivated carrots found in
Americas soon after Columbus’ first visit
• 1600s orange colored carrots frequently
described
• Molecular
• Clear separation between wild and
domesticated; Eastern and Western
• Wild carrots from Central Asia are the
closest genetic relatives to domesticated
carrots
• Domesticated carrot maintains a high level Iorizzo et al., 2013
5. Wild carrot has a heavily
branched, small, white
taproot
Domestication
6. Wild carrot has a heavily
branched, small, white
taproot
Accumulation of lutein and β-carotene
Domestication
7. Wild carrot has a heavily
branched, small, white
taproot
Accumulation of lutein and β-carotene
Reduction of lateral branching and
increased tap root mass/depth
Domestication
9. • Play an essential role in plant life…
• Light collection
• Photoprotection
• Biosynthesis of abscisic acid
• Production of strigolactones
• …and animal life
• Provitamin A
• Anti-cancer effects
• Healthy immune system
• Reduced heart disease
• Can also be used as food colorants, for cosmetics, or in pharmaceuticals
10. • Carrots are one of the highest naturally
occurring sources of β-carotene, an
essential vitamin A precursor
• Carrots can also be red and yellow which
contain lycopene and lutein, respectively
• Carrots have relatively few genomic
resources and the carrot community could
benefit greatly with better tools to improve
key agronomic traits
11. • Transcriptional regulations of genes
controlling carotenoid biosynthesis
and carotenoid degradation
Maize – PSY, ZDS, LCYE, CRTRB, ZEP
K Chandler et al. (2012) Crop Sci
12. • Transcriptional regulations of genes
controlling carotenoid biosynthesis
and carotenoid degradation
Maize – PSY, ZDS, LCYE, CRTRB, ZEP
• Regulation of storage structures
(chromoplasts) that act as
carotenoid sinks
Cauliflower - Or
Lu S et al. (2006) Plant
Cell
K Chandler et al. (2012) Crop Sci
13. • No studies to date, in carrot, have
found a direct link between a
carotenoid biosynthetic gene with
increased lycopene, lutein or β-
carotene accumulation
• Some of these mechanisms require
looking outside of the pathway to
identify potential carotenoid
accumulation candidate genes
14. • No studies to date, in carrot, have
found a direct link between a
carotenoid biosynthetic gene with
increased lycopene, lutein or β-
carotene accumulation
• Some of these mechanisms require
looking outside of the pathway to
identify potential carotenoid
accumulation candidate genes
Need a genome-wide approach!
16. DNA from a
segregating
population
RNA from 3 white, 3
yellow and 3 orange
genotypes
GBS
RNA-
Seq
Run the Tassel
GBS Pipeline
SNPs
Identify
differentially
expressed
genes
Cross reference
and identify
candidates
Genomic
regions of
interest
GLM with
phenotypic data
Run the
Tophat/Cufflinks
Pipeline
17. • 74146 (Wild x Orange)
• 240 F4 individuals
• Segregating for β-
carotene accumulation
• 97837 (White Belgian x
Yellow)
• 270 F2 individuals
• Segregating for lutein
accumulation
19. • 23,650 SNPs
• 5% missing data for marker, 10%
missing data for genotype
Phenotypic class Lutein (μg/g)
1) White (3) 6.90 ± 4.10*
2) Yellow (1) 33.78 ± 13.86
*Values are mean ± standard deviation.
20. • 23,650 SNPs
• 5% missing data for marker, 10%
missing data for genotype
• Region of interest on Chr 5 =
198Kb
Phenotypic class Lutein (μg/g)
1) White (3) 6.90 ± 4.10*
2) Yellow (1) 33.78 ± 13.86
*Values are mean ± standard deviation.
0
2
4
6
8
10
12
-log(P-value)
Genome location
Lutein Accumulation Chr1
Chr2
Chr3
Chr4
Chr5
Chr6
Chr7
Chr8
Chr9
21. • Only one differentially expressed gene in region of interest
• Gene contains 212bp insertion in 2nd exon
• Homologous to Arabidopsis PEL gene – where overexpression
leads to Pseudo-Etiolation in Light
22. • 31,180 SNPs
• 5% missing data for marker, 10%
missing data for genotype
Phenotypic class β-carotene (μg/g)
1) Yellow (3) 0.44 ± 0.49*
2) Orange (1) 99.75 ± 62.05
*Values are mean ± standard deviation.
23. 0
2
4
6
8
10
12
14
16
18
20
-log(P-value)
Genome location
β-Carotene Accumulation Chr1
Chr2
Chr3
Chr4
Chr5
Chr6
Chr7
Chr8
Chr9
• 31,180 SNPs
• 5% missing data for marker, 10%
missing data for genotype
• Region of interest on Chr 7 =
1Mb
Phenotypic class β-carotene (μg/g)
1) Yellow (3) 0.44 ± 0.49*
2) Orange (1) 99.75 ± 62.05
*Values are mean ± standard deviation.
24. DCARv2_Chr7:33261159-33271538 replication protein A1
DCARv2_Chr7:33272106-33274379 pseudogene, similar to putative helicase
DCARv2_Chr7:33294672-33296044 Chalcone synthase
DCARv2_Chr7:33414357-33416815 Polygalacturonase -1
DCARv2_Chr7:33630387-33633403 Plant protein of unknown function (DUF869)
60 Genes in
ROI
Five DEGs
One ROI gene
in
MEP/Caroteno
id pathway
Phenotype 33.0 33.2 33.31 33.36 33.41 33.47 33.63 33.80 33.87 33.94 34.30
Or S Y G T C C T T T . T
Or G C G T C C T T T A K
Or G C G T C C T Y W R K
Y S Y R Y Y Y Y Y W R T
Y S Y R Y Y Y Y Y W R K
Y C T A C T T C C . G T
Y S Y R Y Y Y Y Y W R K
Y S Y R Y Y Y Y Y W R K
Y S Y R Y Y Y Y T T A T
Y S Y R Y Y Y Y C A G T
Y S Y R Y Y Y Y Y W R T
Y S Y R Y Y Y Y Y W R K
1-Deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) catalyzes the first committed
step of the 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway for isoprenoid
biosynthesis
26. • GWAS in ~300 PIs to further fine-map and analyze
linkage disequilibrium around domestication loci
• Verification of differentially expressed genes with qPCR
• Use the CRISPR/Cas9 system to knockout candidate
genes
• Utilize SNPs within candidate genes to create robust co-
dominant markers to be used to evaluate the carrot PI
collection and breeding populations for β-carotene and
lutein accumulation
• Increase breeding efficiency and genebank characterization
28. • Wild carrots have a thin taproot that is
highly branched
• These traits are highly undesirable in current
cultivars and heavily selected against in wide-
crosses
• There are many different carrot cultivar
shapes that are important in different
regions of the world
• Understanding RSA can improve
water- and nutrient-use efficiency
• Need an effective way to phenotype
• 2D imaging!
29. Create, image and genotype F2
mapping population
Adapt existing 2D software, RootNav
and SmartRoot, for carrot
Analyze correlations between RSA
traits and hand-measured traits
Identify genomic regions or genes
associated with economically important
root architecture traits
30. • Create new F2 mapping
population
• B493 (orange inbred) x QAL (wild from
Uzbekistan)
• n = 262
• Wash, label, sample for leaf
tissue (DNA), scan, sample for
root tissue (HPLC)
• Images as saved as JPEGs and
ready to be imported in 2D
image analysis software
Epson Expression 10000XL
~31cm
600 dpi
~44cm
39. • Establish correlations between root traits that can be
integrated into future phenotyping work
• Identify genomic regions or genes associated with
economically important root architecture traits
• Develop molecular markers for desirable root traits to utilize
in the USDA carrot breeding program
40. • People
• Dr. Philipp Simon
• Dr. Douglas Senalik
• Dr. Massimo Iorizzo
• Dr. Megan Bowman
• Rob Kane
• Stephanie Miller
• Dr. Malcolm Bennett
• Dr. Jonathan Atkinson
• Dr. Michael Pound
• Dr. Guillaume Lobet
• Brianna Fochs
• Funding
• National Science Foundation award
1202666
• European Research Council-NSF
Initiative
• Carrot Genome Sequencing Project
• California Fresh Carrot Advisory
Board