Ipomoea

Abstract: Many transcriptional factors harboring the R2R3-MYB domain, basic helix-loop-helix domain, or WD40 repeats have been identified in various plant species as regulators of flavonoid biosynthesis in flowers, seeds, and fruits. However, the regulatory elements of flavonoid biosynthesis in underground organs have not yet been elucidated. We isolated the novel MYB genes IbMYB1 and IbMYB2s from purple-fleshed sweet potato (Ipomoea batatas L. Lam. cv Ayamurasaki). IbMYB1 was predominantly expressed in the purple flesh of tuberous roots but was not detected (or only scarcely) in other anthocyanin-containing tissues such as nontuberous roots, stems, leaves, or flowers. IbMYB1 was also expressed in the tuberous roots of other purple-fleshed cultivars but not in those of orange-, yellow-, or white-fleshed cultivars. Although the orange- or yellow-fleshed cultivars contained anthocyanins in the skins of their tuberous roots, we could not detect IbMYB1 transcripts in these tissues. These results suggest that IbMYB1 controls anthocyanin biosynthesis specifically in the flesh of tuberous roots. The results of transient and stable transformation experiments indicated that expression of IbMYB1 alone was sufficient for induction of all structural anthocyanin genes and anthocyanin accumulation in the flesh of tuberous roots, as well as in heterologous tissues or heterologous plant species.

Abstract: The genus Ipomoea comprises the largest number of species within the Convolvulaceae. Throughout the world Ipomoea is usually estimated to contain c. 500 species (e.g., Mabberley, 1989; McDonald & Mabry, 1992). After our compilation, we believe Ipomoea is more likely to contain 600-700 species. Over half of them are concentrated in the Americas, where the total may approach 500 taxa, mostly native and a few introduced. Although there are recent publications dealing with Ipomoea in the floras of several American countries (O'Donell, 1941-1960b; Austin, 19751991b; Austin & Cavalcante, 1982; Austin & al., 1986; McDonald, unpubl. thesis 1978, unpubl. diss. 1982, 1982-1995; McDonald & Austin, 1990; McDonald & Mabry, 1992; Wilkin, 1995), there is no single reference summarizing all the species currently recognized in the western hemisphere. The purpose of this publication is to make available an updated list with relationships of American Ipomoea species examined thus far. There certainly are more species in the Americas than recognized here, especially in Brazil, Bolivia and Paraguay, but many of these have not been studied since Meisner (1869). Moreover, there are species remaining undescribed and/or undiscovered. Infrageneric placement is given, where known, and a documented American geographical range is provided for each species.