| Summary: | 碩士 === 臺灣大學 === 植物科學研究所 === 95 === Tuberization is an important stage during plant growth and development, especially in tuber crops. As an example, sweet potato (Ipomoea batatas) is characterized with fleshy tuberous roots for nutrient storage. Factors directing the induction of early tuberization have been investigated for a long time in sweet potato. At a glance of the molecular mechanism, one gene encoding 218 amino acids was identified from cDNA-AFLP differential study and then named as Ipomoea batatas MADS-box 1 gene (IbMADS1) based on earlier studies. From sequence alignment and phylogenic analysis, IbMADS1 exhibited a typical type II-MIKC structure, including two conserve domains, MADS-box and K-box. Besides, IbMADS1 was grouped together with other orphan group MADS-box genes, such as AGL17 (Agamous-like 17) in Arabidopsis. After further dissecting the IbMADS1 expression pattern in sweet potato, RNA transcripts were specifically detectable in roots, and the increase of IbMADS1 transcripts was correlated with the early-stage formation of tuberous roots. Southern and Northern analyses were also performed to detect IbMADS1 homologues among tuber-deficient Ipomoea relatives of sweet potato to investigate the evolutionary relationship in tuber formation. In functional study, overexpression assay was conducted in potato (Solanum tuberosum). Interestingly, tuberous swelling along roots was observed in some transgenic potato lines in addition to stem-derived tuber formation. Conclusively, we propose a hypothesis to illustrate the mechanism by which IbMADS1 participates in the initiation of tuberization in sweet potato.
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