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Transcriptome profiling of genes and pathways associated with apical abortion in broccoli
Hsueh-Yu Lu
1
(呂學宇) ,Jhih-Sian
1Department
1
Guo ,Bo-Yu
1
Guo ,Li-Ying
1
Shin ,Jyuan-Yu
Wei
1,Shih-Feng
Fu
1
(傅士峰) *
of Biology, National Chunghua University of Education, Taiwan (彰化師大生物系)
Abstract
2. Anatomy of shoot apical meristems in broccoli lines with apical abortion
Broccoli (Brassica oleracea var. italica) is a floral vegetable with an important
nutritional value due to its content of dietary fiber, antioxidants and anti-carcinogenic
compounds. Apical abortion in broccoli is a highly destructive disorder which occurs in
transplants. However, little is known about the genetic and environmental factors that affect
apical abortion. In this study, we characterized the broccoli cultivars with healthy and aborted
shoots by using comparative transcriptome (RNA-seq) at the early vegetative stage. The
tolerant line for apical abortion (BT001) and sensitive line (BS001) developed normally at
22/18℃ (day/night). However, the sensitive line showed significant apical abortion under
32/28℃. The result suggested that high temperature leads to apical abortion. Transcriptomic
analysis was performed to characterize the differentially expressed genes between the two
lines. Gene ontology analysis showed that response to heat and response to high light
intensity was enriched in heat-tolerant lines. Genes involved in glucosinolate synthesis was
enriched in heat-sensitive lines. Apical abortion in broccoli may result from both
environmental and genetic factors. The genetic markers based on the InDel of the
differentially expressed genes belonging to high light intensity responses were developed. The
DNA molecular markers displayed polymorphisms between the healthy and sensitive lines.
The potential of the DNA markers in molecular breeding was examined. Further investigation
is in progress to demonstrate the use of these genetic markers in identification of apical
abortion varieties.
Fig.
2
Microscopic
examination of shoot apical
meristem in of the apical
abortion-tolerant (BT01) and
-sensitive lines (BS01) at 22
℃ and 32 ℃. The two
broccoli lines were grown
for at different period of
time (30, 40 and 60d) post
germination.
Stereo
microscopy analysis of the
shoot apex from the two
broccoli lines (Upper panel).
Light microscopy of shoot
apical meristem of the two
broccoli lines
(Middle
panel). Scanning electron
micrography of the two lines
(Lower panel).
BT01-enriched gene annotation (22 ℃)
BT01/BS01 fold change>2
BS01-enriched gene annotation (22 ℃)
BS01/BT01 fold change>2
3. Formation of lateral shoots after apical abortion in sensitive lines
Fig. 3 Analysis
of lateral shoot
formation after
after
apical
abortion in the
broccoli
tolerant- (BT01)
and
sensitive
lines (BS01) ) at
22 ℃ and 32 ℃.
Results
1. High temperature resulted in apical abortion in sensitive broccoli lines
Fig. 1 Growth kinetics
and shoot development of
the apical abortion-tolerant
(BT01) and -sensitive
lines (BS01) at 22 ℃ and
32 ℃. The two broccoli
lines were grown for at
different period of time
(30, 40 and 60d) post
germination.
Apical
abortion-tolerant
lines
(BT01) exhibited normal
shoot apex development at
both 22℃ and 32 ℃. The
sensitive lines (BS01)
exhibited normal apex
development at 22 ℃.
Stunt shoot development
was found in apical
abortion-sensitive
lines
(BS01) at 32 ℃. The leaf
numbers of the two
broccoli
lines
were
analyzed from 30 to 60
days at 22℃ and 32 ℃,
respectively.
5. Transcriptomic analysis of apical abortion by RNA-seq
Fig. 5 Transcriptomic analysis of apical abortion in broccoli by RNA-seq. The apical abortion-tolerant (BT01)
and –sensitive broccoli lines (BS01) were grown at 22 ℃ for 4 week. RNA samples were extracted from the shoot
apex from the two broccoli lines and subjected to high-throughput RNA-seq analysis. Differentially expressed
genes with more than 2-fold change from BT01/BS01 and BS01/BT01 were defined as BT01-enriched and BS01 –
enriched, respectively.
6. Genetic marker of broccoli for identify sensitive and tolerant line
4. High-temperature-treated root tissues led to apical abortion
Locus 2541
Locus 2541
BS01 BT01 BS01 BT01
BS02 BT02 BS02 BT02
Locus 11137
BT01
BS01
BT02
BS02
<175 bp
Conclusions and future work
Differential broccoli varieties may exhibit various apical shoot-forming capacities under high temperature. Apical
abortion in broccoli may result from both environmental and genetic factors. Identification of molecular DNA
marker by agrobiotechnology in this study will help local seed breeder to obtain healthy broccoli varieties.
Fig. 4 Grafting analysis of the apical abortion-tolerant (BT01) and –sensitive lines (BS01) at at
22 ℃ and 32 ℃. The high-temperature –treated (32 ℃) broccoli lines served as root stocks while
the sections were collected from the two lines treated with 22 ℃ or 32 ℃.