| Summary: | 碩士 === 國立臺灣大學 === 植物科學研究所 === 93 === Oncidium gower ramsey is an important orchid for cut flower industry in Taiwan. Its pseudobulb is a crucial organ for inflorescence initiation and flower development. In order to investigate the genes expression involved in pseudobulb development and in flowering initiation process, a subtractive cDNA library was generated. cDNA produced from mature pseudobulb was subtracted by cDNA of leaf tissue, then constructed into pGEM-T to generate an EST libraries. More than one thousand ESTs were sequenced and analyzed. Interestingly，the class III peroxidase (POX) genes occupied 12.1.% of total ESTs. They seems to play an important role for flowering. In order to study the physiological function, we isolated nine class III peroxidase cDNA genes from cDNA library. These gene members are show 43-98% identity each other.
We constructed fusion protein of POX to GFP, for bombarding to Onion cell.We found that POX was localized in the intercellular space . We also constructed POX fusion protein vector with GST, and found that it reacted with IAA. Transgenic ectopic express of POXs genes in Arabidopsis with POXs gene caused prominently early flowering within two weeks. Using GC-MS to detect IAA concentration in these transgenic plants, IAA concentration was lower than WT. In Northern blotting analysis, we found that these genes were highly expressed in Oncidium pesudobulb before flower initiation, but expression of these genes were decreased in Oncidium pesudobulb with 3cm flower bud. By RT-PCR analysis, POX13 was specifically expressed in Oncidium pesudobulb and also enhanced in stress condition such as chilling (40C)、ABA(100uM) or H2O2(100uM). These results imply that class III peroxidase in Oncidium may regulate flowering process in Oncidium pseudobulb.
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