To study the interaction between plants and insects I performed the experiments
to find out the counter-defense mechanism of insects when insects were attacked by the
defense protein of plants. Jasmonate (JA) is one of the most important plant hormones
that is involved in plant defense mechanism. I studied to find out the components of JA
signal transduction by T-DNA insertion mutant screening.
In the first study, transcriptional regulation in cowpea bruchid guts during
adaptation to a plant defense protease inhibitor, cowpea bruchid, when fed on a diet
containing the soybean cysteine protease inhibitor soyacystatin N (scN), activates an
array of counter-defense genes to adapt to the negative effects of the inhibitor and regain
its normal rate of feeding and development. A collection of 1,920 cDNAs was obtained
by differential subtraction with cDNAs prepared from guts of the 4th instar larvae of scNadapted
(reared on scN-containing diet) and scN-unadapted (reared on regular scN-free
diet) cowpea bruchids. Subsequent expression profiling using DNA microarray and northern blot analyses identified 94 transcript species from this collection that are
responsive to dietary scN. The full-length cDNA of an scN-inducible cathepsin B-like
cysteine protease was obtained. Its transcriptional response to scN during larval
development contrasts with the pattern of the cathepsin L family, the major digestive
enzymes. These results suggest cathepsin B-like cysteine proteases may play a crucial
role in cowpea bruchid adaptation to dietary scN.
In the second study, screening of mutants that are altered in jasmonate-regulated
signal transduction pathways using Arabidopsis thaliana was performed. Mutant
screening strategy using T-DNA insertion mutagenesis and AVP-LUC as a reporter
enabled to find JA-signal transduction mutants of Arabidopsis thaliana, 9 underregulated
mutants and 6 over-regulated mutants. 20B15 showed reduced VSP1, THI2.1
expression and increased PDF1.2 expression as compared to wild type when treated with
JA. These data strongly suggested that 20B15 is a JA signaling mutant. 49R1, 49R2 and
49R3 had same T-DNA insertion site (At1g53540) and showed about 10-fold higher
AVP-LUC expression level than wild type when JA was treated. Genetic analysis showed
the mutation of these plants was recessive and tight linkage between mutant phenotype
and T-DNA insertion in At1g53540.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1160 |
| Date | 15 May 2009 |
| Creators | Moon, Jaewoong |
| Contributors | Zhu-Salzman, Keyan |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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