1. Physiological and Molecular
Basis of Ethephon to
Enhance Sucrose Content
in Sugarcane
Litao Yang
Guangxi University
liyr@gxu.edu.cn
2014. 02. 16

2. Sugar industry in Guangxi
In 2012/2013 milling season, Guangxi
grew ~1 million ha of sugarcane, and
produced 66.36 million tons of millable
cane and 7.95 million tons of white sugar.
The average cane yield is ~70.0 tons/ha.
Milling season: November ~ April
Socrose content (%): ~ 14.5%

3. Sucrose in Sugarcane
Sucrose accumulate in parenchyma tissue of
sugarcane stalk, up to 60% of its dry weight or
25% (w/w) of its fresh weight
Sucrose yield (t ha-1) =
cane yield (t ha-1) × recoverable sucrose (%) ÷ 100
Recoverable sucrose (%) =
[ sucrose % — (Brix % — sucrose %) ÷ 2 ] × extraction %

4. Major Factors Affecting Sucrose Content
Species and Varieties
Plant age: sucrose concentration progressively
increases towards the base of the stalk
Environment:
light, temperature, water, soil nutrient, weeds,
pests, diseases, farming conditions

5. Increase Sucrose Content in Sugarcane
Breeding programs: New Varieties
Physiological approaches:
Leaf photosynthesis (source)
Enzymes involved in sucrose synthesis;
Sucrose transfer (phloem loading and transport
to the ripening stalk);
Deposition in stalk (carbon partitioning within
the stalk/vacuoles, and also rate of sucrose
remobilization to support vegetative growth )

6. (cited from Wang et al., 2013)
UDP-Glu

7. Plant Hormone: Ethylene
Plant hormones including ABA, ethylene and
GA were involved in the control of sucrose
levels in plant cells.
Ethylene is a gaseous plant hormone that
influences a number of processes in plants
such as seed germination, abscission,
senescence, fruit ripening, response to
stress, and growth.

8. Ethephon is an ethylene releasing compound

9. Molecular biological approaches
Increase Sucrose Content in Sugarcane
To understand the synthesis and accumulation
of sucrose, and the regulation mechanisms of
sucrose accumulation in the stalk;
To identify and characterize the genes involved
in sucrose metabolism and regulation;
To manipulate sugarcane sucrose contents by
transgenesis.

10. Sugarcane
genetypes with
different sucrose
contents
Genomic and
proteomic analysis
Gene
functional
analysis
Physiological
approaches in
sucrose
metabolism and
accumulation
Molecular
regulation
network
The mechanism of
sucrose synthesis,
accumulation and
regulation
Ethylene
induced
Environmenta
l conditions
Relationship
between sucrose
content and
characterization of
physiology and
biochemistry

11. Objectives
1. The effect of ethylene on sucrose content.
2. The physiological mechanism of ethylene
on increase sucrose content.
3. Isolation and functional analysis of
sugarcane genes associated with sucrose
content.
4. Understanding the physiological and molecular
mechanism of sucrose synthesis, accumulation
and regulation in sugarcane.

12. 1. Effect of ethephon on sucrose content in plot
experiment (small area)
Effect of ethephon on increasing sucrose content in mature (internode 8) and
immature (internode 4) internodes in 3 sugarcane varieties (ROC16, early
muturing; GT11, early-intermediate maturing; GT15, intermediate-late
maturing) through foliage sprayed (400 mg/L).

13. Ethephon significantly decreased the reduceing sugar
content in juice of mature (internode 8) and inmature
(internode 4) internodes for 3 varieties

14. 2. Effects of ethephon on sucrose content and yield in
large area of sugarcane
The experiment was conducted at 3 state farms (Jingguang, Liangqi
and Lutang) in total of 2400 ha of sugarcane (plant and ratoon).
Increase sucrose: ~ 1.36%
Increase cane yield: 4.02~6.33%

15. Ethephon increased green leaf numbers and chlorophyll contents
A: Jin-Guang B: Liang-Qi, C: Lu-Tang D: chlorophyll contents

16. SS:sucrose synthase; SPS: sucrose phosphate synthase;
NI:neutral invertase; AI: acid invertase
Sugarcane seedling (ROC16) was foliage sprayed with 200 mg/L of ethephon
3. Effects of ethephon on enzyme activities involved in
sucrose metabolism

17. 4. Effects of ethephon on differential gene expression
Differential gene expression in
sugarcane leaf with ethephon
application and control by cDNA-
AFLP analysis.
Ethephon: 2, 4, 6; Control: 1, 3, 5
Partial differential TDFs
Notes: 1TDF (Transcript derived fragment) codices corresponding to
polymorphism band in polyacrilamide gel; 2Results of BLAST, “--” represents no
homology sequences; 3Identified protein, “--”represents no identified protein; 4
Expect value.

18. The results indicated that ethephon could regulate
the expression of genes related to the primary
metabolism, resistance to disease and stress in
sugarcane.
The differentially expressed genes include:
chitinase I (CHI),
glutathione S-transferase (GST),
auxin-responsice protein (ARP),
light harvesting chlorophyll a/b-binding protein (LHC),
nuclear binding protein (NBP) ,
a set of unknown genes

19. 5. Cloning and expression analysis of
sugarcane sucrose relative genes
(1) Ethylene receptor (Sc-ERS) gene

20. (2) Sucrose phosphate synthase (SofSPSA and SofSPSB) gene

21. (3) Soluble acid invertase (SoSAI1) gene
Expression analysis of SoSAI1 in different organs and growth stages of sugarcane.
A: Elongation stage; B: Technical maturing stage; C: Physiological maturing stage;
D: Physiological matured stage 1-3: leaves at immature, maturing and matured,
respectively; 4-6: internodes of immature, maturing and matured; 7: rachis; 8:
inflorescence.

22. (4) alkaline/neutral invertase (SoNIN1)
Expression of SoNIN1 gene in different sugarcane organs.
1–7: internodes of +1, +6, +11, +16, +21, +26, +31, respectively;
8-11: leaves of top leaf roll, +1, +3, +6, respectively;
12: rachis; 13: inflorescence; 14: bud.

23. 1. Biological funtional analysis of sugarcane
sucrose relative genes (localization and
transgenetics)
2. Genomic and proteomic analysis of
sugarcane genetypes with different sucrose
contents
3. Set up the network of sucrose synthesis,
accumulation and regulation
Further Research

24. Acknowledgements
PI: Prof. & Dr. Yang-rui LI,
GXAAS: Drs. Bao-Qing Zhang, Yuan-Wen Wei, Dong-Liang Huang,
Prof. Qiu-zhen Zhu
GXU: Prof. Ai-Qin Wang,
Ph.D. students: Jun-Qi Niu
State Farms: Wu-jia Cen, Zhi-biao LanN, Hua-ming Guang,
Zhong-Bo Huang
Funding:
National Science and Technology Program
National Nature Science Foundation
Guangxi R & D Research Program

25. Thank you!