A maize landrace that emits defense volatiles in response to herbivore eggs possesses a strongly inducible terpene synthase gene
2017
Maize (Zea mays) emits volatile terpenes in response to insect feeding and egg deposition
to defend itself against harmful pests. However, maize cultivars differ strongly in
their ability to produce the defense signal. To further understand the agroecological
role and underlying genetic mechanisms for variation in terpene emission among
maize cultivars, we studied the production of an important signaling component (E)-caryophyllene
in a South American maize landrace Braz1006 possessing stemborer
Chilo partellus egg inducible defense trait, in comparison with the European maize line
Delprim and North American inbred line B73. The (E)-caryophyllene production level
and transcript abundance of TPS23, terpene synthase responsible for (E)-caryophyllene
formation, were compared between Braz1006, Delprim, and B73 after mimicked herbivory.
Braz1006–TPS23 was heterologously expressed in E. coli, and amino acid sequences
were determined. Furthermore, electrophysiological and behavioral responses
of a key parasitic wasp Cotesia sesamiae to C. partellus egg-induced
Braz1006 volatiles
were determined using coupled gas chromatography electroantennography and
olfactometer
bioassay studies. After elicitor treatment, Braz1006 released eightfold
higher (E)-caryophyllene
than Delprim, whereas no (E)-caryophyllene
was detected in
B73. The superior (E)-caryophyllene production by Braz1006 was positively correlated
with high transcript levels of TPS23 in the landrace compared to Delprim. TPS23
alleles
from Braz1006 showed dissimilarities at different sequence positions with
Delprim and B73 and encodes an active enzyme. Cotesia sesamiae was attracted to
egg-induced
volatiles from Braz1006 and synthetic (E)-caryophyllene. The variation in
(E)-caryophyllene
emission between Braz1006 and Delprim is positively correlated
with induced levels of TPS23 transcripts. The enhanced TPS23 activity and corresponding
(E)-caryophyllene
production by the maize landrace could be attributed to
the differences in amino acid sequence with the other maize lines. This study suggested
that the same analogous genes could have contrasting expression patterns in
different maize genetic backgrounds. The current findings provide valuable insight not only into genetic mechanisms underlying variation in defense signal production but
also the prospect of introgressing the novel defense traits into elite maize varieties for
effective and ecologically sound protection of crops against damaging insect pests.
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
47
References
18
Citations
NaN
KQI