| Summary: | 碩士 === 國立中興大學 === 生物科技學研究所 === 103 === Geminiviruses in the genus Begomovirus are single-stranded circular DNA viruses transmitted by whiteflies and infect dicotyledonous plants, causing great agricultural losses by inflicting severe symptoms including stunting and leaf curling. The shoot apical meristem (SAM) of angiosperm is the origin for developing new buds and leaves, and thus involved in leaf curling symptoms. It has been shown that adaxial domain of leaves would be enlarged by the misexpression of PHABULOSA (PHB), PHAVOLUTA (PHV), and REVOLUTA (REV) genes, which encode class III homeodomain-leucine zipper (HD-ZIPIII) proteins in Arabidopsis. Therefore, the aim of this study is to investigate whether PHV proteins are involved in inflicting leaf curling symptoms by begomoviruses in N. benthamiana. For the detection of PHV proteins in plants, this research have cloned PHV gene of N. benthamiana, expressed the PHV protein, raised anti-PHV polyclonal antibody and ensured its sensitivity through western blot. To test whether PHV is involved in leaf curling symptom infliction by begomoviruses, the expression of PHV gene was knocked down by virus induced gene silencing (VIGS), and then infected with Ageratun yellow vein virus (AYVV) or Tomato leaf curl virus (TLCV) by agroinfiltration. The result revealed that the PHV knock-down plants exhibited delayed development of disease symptoms compared to wild type plants. In contrast, plants infected with AYVV or TLCV and before knocking down PHV gene showed similar symptoms as wild type plants. Analysis of PHV expression on buds and leaves infiltrated AYVV or TLCV revealed that the expression of PHV in infected plants was higher than in healthy ones. It has been shown that PHV and begomovirus C4 protein are both involved in the brassinosteroid signaling pathway which modulate leaf development. The results of this study suppors the possibility that begomoviruses may modulate leaf curling symptoms indirectly through brassinosteroid signaling pathway. It is expected that through this study, alternative methods for modulating leaf curling symptoms might be developed for the management of begomovirus diseases.
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