| Summary: | 碩士 === 國立中興大學 === 生物科技學研究所 === 102 === Begomoviruses, whitefly-transmitted members of the family Geminiviridae, harbor single-stranded circular DNA genomes and cause serious economical damages in numerous important dicotyledonous crops worldwide. Our previous studies found that Nicotiana benthamiana plants infected by Agerayum yellow vein virus (AYVV) displayed severe upward leaf curling symptom. In ontrast, Tomato leaf curl virus (TLCV) and Squash leaf curl virus (SqLCV) caused downward leaf curling symptom on N. benthamiana. The C4 proteins of these viruses were found to be involved in the regulation of the directions of leaf curling symptoms. Several host factors, including Chloroplast photosynthetic oxygen-evolving protein (CPOEP), have been identified to interact with the C4 proteins of various begomoviruses. Among the host factors, CPOEP has been shown to be involved in the symptom expression of some RNA viruses. However, whether CPOEP plays any role in the modulation of symptoms inflicted by DNA viruses remains to be elucidated. Therefore, the objective of this study is to investigate the molecular interactions between CPOEP and C4 proteins of AYVV, TLCV, and SqLCV. The CPOEP gene of N. benthamiana was amplified and cloned in the pET21d vector. The CPOEP protein was then over-expressed in Escherichia coli, purified, and used as antigens to raise specific antisera. Far-western blot analysis using CPOEP or various C4 proteins as probes confirmed the differential interactions between viral C4 proteins and CPOEP. By using the yeast two-hybrid analyses, it was revealed that the middle portion and the C-terminus of CPOEP differentially interact with the C4 protein of AYVV and TLCV, which might also be involved in the modulation of leaf curling symptoms. In contrast, the N-terminus of CPOEP is not involved in the interactions. The examination of mRNA and protein expression levels of CPOEP in plants infected with different begomoviruses is currently underway. It is expected that the results will provide further insight into the mechanisms for the modulation of symptoms.
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