Sucrose importation into laticifers of Hevea brasiliensis, in relation to ethylene stimulation of latex production.
OBJECTIVE
The major economic product of Hevea brasiliensis is a rubber-containing cytoplasm (latex), which flows out of laticifers (latex cells) when the bark is tapped. The latex yield is stimulated by ethylene. Sucrose, the unique precursor of rubber synthesis, must cross the plasma membrane through specific sucrose transporters before being metabolized in the laticifers. The relative importance of sucrose transporters in determining latex yield is unknown. Here, the effects of ethylene (by application of Ethrel on sucrose transporter gene expression in the inner bark tissues and latex cells of H. brasiliensis are described.


METHODS
Experiments, including cloning sucrose transporters, real time RT-PCR and in situ hybridization, were carried out on virgin (untapped) trees, treated or untreated with the latex yield stimulant Ethrel.


RESULTS
Seven putative full-length cDNAs of sucrose transporters were cloned from a latex-specific cDNA library. These transporters belong to all SUT (sucrose transporter) groups and differ by their basal gene expression in latex and inner soft bark, with a predominance of HbSUT1A and HbSUT1B. Of these sucrose transporters, only HbSUT1A and HbSUT2A were distinctly increased by ethylene. Moreover, this increase was shown to be specific to laticifers and to ethylene application.


CONCLUSIONS
The data and all previous information on sucrose transport show that HbSUT1A and HbSUT2A are related to the increase in sucrose import into laticifers, required for the stimulation of latex yield by ethylene in virgin trees.
Dusotoit-Coucaud
Anaïs
A
UMR 547 PIAF, INRA, Université Blaise Pascal, 24 avenue des Landais, 63177 Aubière Cedex, France.
Brunel
Nicole
N
Kongsawadworakul
Panida
P
Viboonjun
Unchera
U
Lacointe
André
A
Julien
Jean-Louis
JL
Chrestin
Hervé
H
Sakr
Soulaïman
S
D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005030:Ethylenes / Q000494:pharmacology*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism; D028482:Hevea / Q000166:cytology* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D017403:In Situ Hybridization; D007840:Latex / Q000096:biosynthesis* / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000187:drug effects; D010802:Phylogeny; D024301:Plant Bark / Q000187:drug effects / Q000235:genetics; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism*; D014197:Trees / Q000187:drug effects / Q000235:genetics
D018076:DNA, Complementary; D005030:Ethylenes; D007840:Latex; D026901:Membrane Transport Proteins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012333:RNA, Messenger; D013395:Sucrose; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase; D005974:Glutamate-Ammonia Ligase